Efficacy of an automated technology at detecting early postpartum estrus events: Can we detect resumption of cyclicity?

The objective of this observational study was to evaluate the efficacy of a neck-mounted automated activity monitor (AAM) at detecting early postpartum resumed ovarian cyclicity. A total of 192 lactating cows (primiparous = 73 and multiparous = 119) were enrolled in this study. Cows were continuously monitored by a neck-mounted AAM early postpartum (7 to 30 d in milk; DIM). Calving was classified as assisted (forced extraction of a calf) or unassisted (normal calving). Retained fetal membrane, metritis, hyperketonemia, clinical mastitis, and milk production were recorded. Cows were classified as healthy (i.e., no disease events) or sick (i.e., any disease event). Estrus events were alerted by the AAM using a proprietary algorithm set by the AAM company. Blood samples, from the coccygeal vein, were collected at 15, 18, 21, 24, 28, and 30 DIM for progesterone (P4) analysis. Resumption of cyclicity was considered when P4 concentration was ≥1 ng/mL on any collection day. Cows were considered anovular when P4 concentration was <1 ng/mL on all collection days. Cows were classified as true positive: P4 ≥ 1 ng/mL and at least one estrus alert; false positive: P4 < 1 ng/mL and at least one estrus alert; true negative: P4 < 1 ng/mL and no estrus alerts; and false negative: P4 ≥ 1 ng/mL and no estrus alerts. Statistical analyses were performed by frequency distribution and mixed effects logistic regression procedures on SAS (SAS Institute Inc.). The specificity, sensitivity, accuracy, and positive predictive value of the sensor to detect cows that had resumed cyclicity were 84.0%, 34.1%, 52.1%, and 79.2%, respectively. Out of the 192 cows, 35.9% (69/192) were anovulatory and 37.5% (72/192) had no estrus events between 7 to 30 DIM. Healthy cows were more likely to resume cyclicity in early lactation compared with cows that were sick (78.3 ± 1.9 vs. 32.8 ± 3.1%, respectively) independent of parity. In conclusion, the sensor had a high specificity for detecting anovular cows, but it had lower sensitivity, and thus was not effective at detecting cyclic cows, perhaps due to silent ovulation early postpartum.

Effect of 2 dosages of prepartum cholecalciferol injection on blood minerals, vitamin D metabolites, and milk production in multiparous dairy cows: A randomized clinical trial

The objective of the present study was to evaluate the effect of 2 dosages of prepartum cholecalciferol injection on blood minerals, vitamin D metabolites, and milk production. Cows entering their second or greater lactation (n = 158) were randomly assigned to a control group (CON) or one of 2 treatment groups receiving either 6 × 106 IU (6VitD) or 12 × 106 IU (12VitD) cholecalciferol intramuscularly on d 275 ± 1.2 (SD) of gestation. Concentrations of serum total Ca (tCa), phosphate, and Mg were determined on 1, 2, 3, 5, 7, and 10 d in milk (DIM). For a subsample of 30 cows entering the third lactation (n = 10/group), these samples were analyzed for cholecalciferol, 25-hydroxycholecalciferol (25-OHD3), and 24,25-dihydroxycholecalciferol (24,25-[OH]2D3). In these cows, we also determined 1,25-dihydroxycholecalciferol (1,25-[OH]2D3), the biologically most active metabolite, on 1, 2, 3, and 5 DIM. Repeated measures ANOVA was performed to evaluate the effect of different dosages of cholecalciferol on blood minerals, vitamin D metabolites, and milk yield over the first 5 test days after calving. Binary outcomes such as retained placenta and metritis were analyzed using a chi-squared test. Although the 12VitD treatment increased tCa concentrations on 1, 2, and 3 DIM compared with CON, administration of 6VitD increased tCa concentrations only on 1 DIM. Compared with CON cows and 6VitD cows, 12VitD cows had greater serum phosphate concentration during the first 10 DIM. Furthermore, 6VitD cows had greater serum phosphate concentrations compared with CON cows. On the contrary, 12VitD cows had lower serum Mg concentrations during the first 10 DIM compared with CON and 6VitD cows. Cholecalciferol was increased by the treatment and decreased quickly until 10 DIM. In respect to 25-OHD3, the 6VitD treatment resulted in a 4.1-fold increase in comparison to the CON group, while a 6.5-fold increase was observed in 12VitD animals. The vitamin D metabolite 24,25-(OH)2D3 increased linearly with 25-OHD3 serum levels, resulting in the highest concentrations in the 12VitD group. An increase of 1,25-(OH)2D3 until 3 DIM was observed in all cows. However, this rise was most pronounced in the CON group. The incidence of retained placenta was 1.9%, 11.5%, and 29.6%, and that of metritis was 11.5%, 15.4%, and 31.5% for CON, 6VitD, and 12VitD cows, respectively. Although none of the treated cows exerted clinical signs of hypocalcemia, one cow in CON incurred clinical hypocalcemia. Cows of the 12VitD group had a lower milk yield over the first 5 monthly test days compared with the control and 6VitD group (42.2 ± 0.5, 42.0, ± 0.5 and 40.7 ± 0.5 kg for control cows, 6VitD cows and 12VitD cows, respectively). Although no negative side effects were observed in 6VitD cows, we do not recommend the general application of 6 × 106 IU cholecalciferol before calving as positive effects on calcium homeostasis were marginal and restricted to the first DIM. The present findings confirm that the application of 12 × 106 IU cholecalciferol negatively affected milk production on this farm.

Association between genomic daughter pregnancy rate and expected milk production on the resumption of estrus behavior in Holstein cattle

The objective of this observational study was to evaluate estrous expression at the first estrus occurring between 7 to 30 d in milk (DIM), as detected by an automated activity monitor (AAM), and its association with genomic daughter pregnancy rate (GDPR) and genomic expected milk production (GEM) in lactating dairy cows. A total of 4,119 lactations from 2,602 Holstein cows were included. Cows were enrolled as first lactation (n = 1,168), second lactation (n = 1,525) and third and greater lactation (n = 1,426). Hair samples were collected from the tail switch, and cows were genotyped using an SNP platform (Clarifide, Zoetis, São Paulo, SP, Brazil). Postpartum cows were examined daily by the farm personnel from calving until 10 DIM. Calving was classified as assisted (forced calf extraction) and unassisted (normal calving). Retained fetal membranes (RFM), hyperketonemia (KET), and left displaced abomasum (LDA) were also recorded. Mean GDPR (± SD) was -0.29 ± 1.4, and the intensity and duration of the first estrus event was 15.9 ± 13.1 x-factor (intensity unit measurement) and 11.1 ± 3.8 h, respectively. Cows that had greater GDPR had greater intensity and longer duration of estrus at the alert, independent of parity. Overall resumption of estrous expression, between 7 to 30 DIM, was 41.2% (1,695/4,119), where 58.8% (2,424/4,119) did not have an estrus event, 31.0% (1,274/4,119) of cows had one event of estrus, and 10.2% (421/4,119) of cows had 2 or more events of estrus early postpartum. Mean DIM (± SD) at first estrus event, detected by the AAM, was 19.4 ± 4.4 d. Days in milk at first event for cows with one event was 20.7 ± 1.6 d and 15.9 ± 3.1 d for cows with 2 or more events of estrus. First lactation cows were more likely to have an estrus event early postpartum when compared with second and third and greater lactation cows (45.2 ± 1.4% [530/1168] vs. 41.6 ± 1.3% [636/1525] vs. 37.2 ± 1.3% [529/1426], respectively). There was an interaction of parity and GDPR on the proportion of cows demonstrating an early postpartum estrus. There was no difference in the proportion of cows with an early postpartum estrus between those with assisted or unassisted calving, RFM, or LDA. However, cows that had KET were less likely to have an alert early postpartum when compared with cows that did not have KET. Mean genomic expected milk production (± SD) was 256.8 ± 600.1 kg. There was no interaction between GEM and parity on estrous expression (i.e., intensity and duration). There was no interaction between GEM and GDPR on the proportion of estrus early postpartum.

INVITED REVIEW: Nutritional and management factors that influence colostrum production and composition in dairy cows

Colostrum is a rich source of nutritional and non-nutritional components and is recognized as essential to transfer passive immunity to newborn calves. Because of the individual and seasonal variability in colostrum yield and composition, maintaining an adequate supply of high-quality colostrum year-round remains a challenge for commercial dairy producers. In this narrative review, we described the individual, seasonal, and herd-level variability of colostrum production and summarized the association between individual animal factors such as parity, sex of the calf, calf birth weight, as well as indicators of the cow's metabolic status and the yield and composition of colostrum. Further, we reviewed the current knowledge on the influence of prepartum nutrition and management strategies on colostrum production. Research on the metabolizable energy and protein supplied in the prepartum diet as well as into the inclusion and source of vitamins, minerals, and feed additives suggests prepartum nutrition influences the yield, quality, and composition of colostrum. Furthermore, the prepartum environment and dry period length remain influential factors in the production of colostrum. However, additional research is needed to understand the mechanisms by which prepartum nutrition and management affects colostrum production. Lastly, time to colostrum harvest and oxytocin administration as well as the current knowledge on the effect of heat-treatment and colostrum storage strategies on colostral components were discussed. To conclude, we identify critical gaps in knowledge for future focus of investigation in colostrum research.

Association of transition cow health with pregnancy per artificial insemination and pregnancy loss in Holstein cows submitted to a Double-Ovsynch protocol for first service

This observational study was conducted to evaluate the effect of transition cow health on pregnancy per artificial insemination (P/AI) and pregnancy loss (PL) in cows submitted to a Double-Ovsynch protocol (DO) for first service. Lactating Holstein cows (n = 15,041) from one commercial dairy farm in northern Germany between January 2015 to December 2021 were enrolled into a modified Double-Ovsynch protocol (GnRH, 7 d later PGF2α, 3 d later GnRH, 7 d later GnRH, 7 d later PGF2α, 24 h later PGF2α, 32 h later GnRH, and 16 to 18 h later timed artificial insemination) for first service at 72 ± 3 d in milk. Pregnancy was diagnosed at 32 and 60 d post-AI via transrectal ultrasonography. Pregnancy loss was defined as the proportion of cows diagnosed pregnant 32 d post-artificial insemination that were diagnosed nonpregnant 60 d post-artificial insemination. Health-related events (i.e., milk fever [MF], hyperketonemia [KET], retained fetal membranes [RFM], metritis, mastitis, left displaced abomasum [LDA]) were assessed by farm personnel using standard operating procedures. Multivariable logistic regression was used for testing potential associations between transition cow health event occurrence and outcome variables, including P/AI and PL. Three separate models were built for cows in first lactation, second lactation, and ≥third lactation. Overall, 20.0% (885/4,430), 34.9% (1,391/3,989), and 53.9% (3,570/6,622) of cows had at least one transition cow health event for first, second, and ≥third lactations, respectively. The most prevalent transition cow health event for first-lactation cows was metritis (10.7%; [473/4,430]), whereas second-lactation cows suffered mostly from mastitis (16.6%; [664/3,989] and KET (16.6%; [661/3,989]), and cows with ≥third lactations were mostly affected by KET (33.2%; [2,198/6,622]). We observed a negative association between inflammatory disorders (i.e., RFM, metritis, mastitis) and P/AI in all cows irrespective of parity. Metabolic disorders (i.e., MF, KET, LDA) were negatively associated with P/AI only in multiparous cows. Irrespective of parity, only uterine diseases (i.e., RFM, metritis) were significantly associated with PL. These results show that enrolling cows into a fertility protocol, such as DO, cannot overcome the carryover effects of inflammatory and metabolic disorders on P/AI and PL and highlight the importance of optimizing transition cow health as a prerequisite for achieving high fertility in a DO protocol.

Association between a pyroelectric infrared sensor monitoring system and a 3-dimensional accelerometer to assess movement in preweaning dairy calves

The objective of this study was to correlate movement assessed by a pyroelectric infrared sensor system in preweaning dairy calves with lying and standing time assessed by a 3D accelerometer considering the temperature-humidity index (THI). A total of 35 dairy calves (1-7 d of age) were enrolled in the study and 20 calves were included in the final analyses. The lying and standing time of the calves was monitored with a 3D accelerometer (Hobo Pendant G Data Logger, Onset Computer Corporation, USA), which was used as the gold standard reference. The infrared sensor monitoring system (IMS; Calf Monitoring System, Futuro Farming GmbH, Germany) was fixed to the fence of the calf hutch within the calf's reach. Temperature-humidity was monitored with 2 validated THI sensors inside and on outside of each calf hutch. Additionally, one THI sensor was located near the calf hutches. The observation period lasted 14 consecutive days. The average standing time assessed by the 3D accelerometer was 13.4 ± 12.7 (mean ± standard deviation) min/h and the average lying time was 46.6 (±12.7) min/h. The median (25th percentile; 75th percentile) number of movements measured by the IMS was 360 (60; 919) movements per hour. Number of movements per hour measured by the IMS was compared with data obtained with a validated 3D accelerometer. The Pearson correlation coefficient between both standing and lying time and the number of movements was r = 0.85 and r = -0.85, respectively. The Pearson correlation coefficients were only slightly influenced by THI (low THI [<68]: r = 0.86; medium THI [68-72]: r = 0.85; high THI [>72]: r = 0.81). Our data show that the number of movements of dairy calves measured by IMS were highly correlated with the chosen gold standard reference method. High THI slightly affects the measurement accuracy of IMS.

Evaluation of laboratory and on-farm tests to estimate colostrum quality for dairy cows

The objectives of this study were to evaluate different analytical methods to determine colostrum quality in dairy cattle, including one laboratory-based method (ELISA) and 4 on-farm tests. We hypothesized that the colostral IgG concentration using different analytical methods, such as ELISA (mg/mL), digital Brix refractometer (% Brix), colostrometer (specific gravity and mg/mL), an outflow funnel (seconds), and a lateral flow assay (mg/mL), were highly correlated with the reference method, radial immunodiffusion (RID; mg/mL) and would generate comparable results. Colostrum samples were collected from 209 Holstein Friesian cows on 2 commercial dairy farms in Germany. Colostrum weight and colostrum temperature were measured. Test characteristics, such as optimum thresholds, sensitivity, specificity, and area under the curve (AUC) were determined using a receiver operating characteristic curve analyses for each test. Out of 209 colostrum samples assessed by RID, 186 (89%) samples had high quality (≥50 mg IgG/mL), while 23 colostrum samples (11%) showed poor quality with IgG concentrations less than 50 mg/mL. The mean IgG concentration (±SD) was 101.3 ± 45.9 mg/mL and the range was 6.0 to 244.3 mg/mL. The Pearson correlation coefficient (r) between RID and ELISA was r = 0.78. In comparison to RID, Pearson correlation coefficients for the on-farm tests were: r = 0.79 (digital Brix refractometry), r = 0.58 (colostrometer: specific gravity), r = 0.61 (colostrometer: temperature corrected), r = 0.26 (outflow funnel) and r = 0.43 (lateral flow assay), respectively. The optimal threshold to identify high-quality colostrum using ELISA was 50.8 mg/mL with sensitivity 91.3%, specificity 92.3%, and AUC of 0.94. For the on-farm tests sensitivity ranged from 95.7% (Brix refractometry) to 60.9% (lateral flow assay). Specificity ranged from 88.6% (lateral flow assay) to 75.9% (colostrometer: temperature corrected). The AUC ranged from 0.93 (Brix refractometry) to 0.73 (outflow funnel). Based on the AUC, ELISA (0.94) and Brix refractometry (0.93) can be considered highly accurate. In conclusion, the ELISA is accurate to assess colostrum quality. Regarding the on-farm tests only the digital Brix refractometer and the colostrometer were adequate to determine colostrum quality.

Association between transfer of passive immunity, health, and performance of female dairy calves from birth to weaning

The objective of this observational study was to compare calf health, average daily weight gain, and calf mortality considering the proposed categories of transfer of passive immunity (TPI) by the consensus report of Lombard et al. (2020). The consensus report defines 4 categories of passive immunity (excellent, good, fair, and poor) of calves obtained after colostrum ingestion. The association between the 4 TPI categories was analyzed on calf health (i.e., hazards for morbidity and mortality), and average daily weight gain (ADG) of female Holstein Friesian calves during the first 90 d of age. A further aim of this study was to examine the effects of calving-related factors, such as dystocia or winter season, on TPI status. We hypothesized that calves with excellent TPI have greater ADG, lower risks for infectious diseases such as neonatal diarrhea, pneumonia, and omphalitis, and lower mortality rates. This observational study was conducted from December 2017 to March 2021. Blood was collected from 3,434 female Holstein Friesian dairy calves from 1 commercial dairy farm. All female calves aged 2 to 7 d were assessed for TPI status by determination of total solids (TS) in serum via Brix refractometry by the farm personnel once a week. Passive immunity was categorized according to Lombard et al. (2020) with excellent (≥9.4% Brix), good (8.9-9.3% Brix), fair (8.1-8.8% Brix), or poor TPI (<8.1% Brix). For the analysis of ADG and calving ease 492 or 35 calves had to be excluded due to missing data. The distribution of calves according to TPI categories was as follows: 4.8% poor (n = 166), 29.5% fair (n = 1,012), 28.3% good (n = 971), and 37.4% excellent (n = 1,285). From the calving-related factors, parity of the dam, calving ease, birth month, calving assistance by different farm personnel, and day of life for TPI assessment were significantly associated with TS concentration. Out of 3,434 calves, 216 (6.3%) had diarrhea, and 31 (0.9%) and 957 (27.9%) suffered from omphalitis and pneumonia during the first 90 d of life, respectively. Overall, the morbidity during the preweaning period was 32.6% (n = 1,118), and the mortality was 3.1% (n = 107). The ADG was 0.90 ± 0.15 kg with a range of 0.32 to 1.52 kg. The Cox regression model showed that calves suffering from poor TPI tended toward a greater hazard risk (HR) for diarrhea (HR = 1.57, 95% CI: 0.92-2.69) compared with calves with excellent TPI. Calves suffering from TPI had a greater HR for pneumonia (HR = 2.00, CI: 1.53-2-61), overall morbidity (HR = 1.99, CI: 1.56-2.55), and mortality (HR = 2.47, CI: 1.25-4.86) in contrast to excellent TPI. Furthermore, calves with good and fair TPI had significantly greater HR for pneumonia (good TPI: HR = 1.35, CI: 1.15-1.59; fair TPI: HR = 1.41, CI: 1.20-1.65) and overall morbidity (good TPI: HR = 1.26, CI: 1.09-1.47; fair TPI: HR = 1.32, CI: 1.14-1.53) compared with the excellent TPI category. Average daily weight gain during the first 60 d of life was associated with TPI categories. Calves with excellent and good TPI status had ADG of 0.90 ± 0.01 kg/d and 0.92 ± 0.01 kg/d (mean ± SE), respectively. The ADG of calves with fair TPI status was 0.89 ± 0.01 kg/d, and calves suffering from poor TPI had 0.86 ± 0.01 kg/d. Average daily weight gain differed in calves with poor TPI compared with the other categories. Fair and excellent TPI differed additionally from good TPI. We found no statistical difference between the TPI categories fair and excellent. In conclusion, poor TPI was associated with higher morbidity and mortality during the first 90 d of life. Furthermore, calves with fair, good or excellent TPI had greater ADG.

Associations between days in the close-up group and milk production, transition cow diseases, reproductive performance, culling, and behavior around calving of Holstein dairy cows

The objective of experiment I was to evaluate the association between days in the close-up group (DINCU) and milk production, early lactation diseases, reproductive performance, and culling. In experiment II behavioral changes associated with DINCU were evaluated using a neck-mounted sensor (Smarttag neck, Nedap Livestock Management, Groenlo, the Netherlands). Cow-lactations of 28,813 animals from 14,155 individual cows of 2 farms in northern Germany and western Slovakia, calving between January 2015 and December 2020, were included in the study. After exclusion of cows with a gestation length <262 and >292 d and cows with >42 DINCU data from 8,794 and 19,598 nulliparous and parous cows, respectively, were available for final statistical analyses. To analyze the association between DINCU and second test-d 305-d mature-equivalent milk projection, linear mixed models were calculated. Binary data (i.e., clinical hypocalcemia, hyperketonemia, retained placenta [RP], acute puerperal metritis [APM], mastitis, left displaced abomasum [LDA], first service pregnancy risk) were analyzed using logistic regression models. To analyze the association between DINCU and culling or death during the first 300 DIM Cox proportional hazards were used. To analyze the association between DINCU and behavior 7 d before to 7 d after calving (i.e., activity, inactivity, eating, ruminating time), linear mixed models were calculated. Nulliparous cows with a short (<10 DINCU) and a long stay (>30 DINCU) in the close-up group had a lower milk production an increased risk for hyperketonemia, RP, and APM compared with nulliparous cows with DINCU between 21 to 28 d. Parous cows with a short (<10 DINCU) and a long stay (>30 DINCU) in the close-up group had a lower milk production, an increased risk for RP and mastitis, a reduced first service pregnancy risk, and an increased culling risk, compared with parous cows with DINCU between 21 to 28 d. Furthermore, the risk for clinical hypocalcemia and LDA was increased in parous cows with >30 DINCU compared with parous cows with <30 DINCU. The risk for APM was increased in parous cows with <10 DINCU compared with parous cows with >10 DINCU. In nulliparous cows no association was found between DINCU and the risk for left displaced abomasum and mastitis. In experiment II, cows with 7 and 35 DINCU had an impaired behavior around calving compared with cows with 14, 21, and 28 DINCU. During the last 7 d before parturition, these cows were more inactive and had a reduced eating and ruminating time. After calving, cows with 7 DINCU spent less time eating. In conclusion, cows with <10 DINCU and cows with >30 DINCU had a lower milk production, a higher risk to incur diseases and an impaired behavior, especially before calving.

Effect of a progesterone-releasing intravaginal device (PRID) for 8 days during a modified Ovsynch protocol on pregnancy outcomes in lactating Holstein cows

Our objective was to evaluate the effect of a progesterone-releasing intravaginal device (PRID) in a 7-d Ovsynch protocol on pregnancy per artificial insemination (P/AI) and pregnancy loss, compared with a standard 7-d Ovsynch protocol without progesterone supplementation. We hypothesized that progesterone supplementation during an Ovsynch protocol would increase P/AI and decrease pregnancy loss. Data were collected on lactating Holstein cows (n = 716) that either received a 7-d Ovsynch protocol (control: d 0, 100 µg of GnRH; d 7, 500 µg of cloprostenol; d 9, µg of GnRH; n = 360) or a modified Ovsynch protocol with addition of a PRID (PRIDsynch; d 0, 100 µg of GnRH + PRID; d 7, 25 mg of dinoprost; d 8, PRID removal; d 9, 100 µg of GnRH; n = 356). All cows received timed artificial insemination (TAI) approximately 16 h after the second GnRH treatment. Pregnancy diagnosis was performed via ultrasonography on d 38 ± 3 after TAI and rechecked on d 80 ± 7 after TAI. Reproductive performance differed between treatments, with PRIDsynch cows having greater (38.9%) P/AI compared with control cows (31.7%) at d 38 ± 3 and also at d 80 ± 7 (34.6% vs. 28.9%, for PRIDsynch and control cows, respectively). Pregnancy loss did not differ among treatments.

Evaluating different methods of serum collection to detect failed transfer of passive immunity in newborn calves via refractometry

The objective of the study was to compare 4 different methods of serum collection to assess failed transfer of passive immunity (FTPI) in dairy calves. We hypothesized that centrifuged serum, filtered serum and clotted serum at room temperature, and clotted serum at refrigerator temperature measured with Brix refractometry would highly correlate with IgG concentration assessed by radial immunodiffusion (RID; gold standard) in centrifuged serum. Blood samples were collected from 321 newborn dairy calves. In centrifuged serum (r = 0.88), serum clotted at room temperature (20.2°C ± 6.47; r = 0.86), serum clotted at refrigerator temperature (7.6°C ± 0.91; r = 0.87), and filtered serum (r = 0.70), total solids (TS) in % Brix, and IgG concentrations measured with RID were highly correlated. Regarding the refractometry results among the different serum types, the TS results of serum clotted at room temperature, clotted at refrigerator temperature, and filtered serum showed high correlation coefficients compared with the TS results of centrifuged serum (r = 0.99, r = 0.98, and r = 0.89), respectively. The test characteristics of clotted serum were as accurate as centrifuged serum and generate comparable results. Filtered serum was slightly less accurate. All serum types are valid methods to detect an FTPI in dairy calves, if the specific Brix thresholds for each serum type are considered. Nevertheless, serum clotted at refrigerator temperature should not be the preferred method to avoid the risk of hemolysis.

Association of activity and subsequent fertility of dairy cows after spontaneous estrus or timed artificial insemination

The objective of this observational study was to evaluate the association between increased physical activity at first artificial insemination (AI) and subsequent pregnancy per AI (P/AI) in lactating Holstein cows following spontaneous estrus or a timed AI (TAI) protocol. We also wanted to identify factors associated with the intensity of activity increase (PA) captured by automated activity monitors (AAM) and fertility. Two experiments were conducted, in which cows either were inseminated based on the alert of the AAM system (AAM cows) or received TAI following a 7-d Ovsynch protocol (TAI cows) if not inseminated within a farm-specific period after calving. Experiment 1 included 2,698 AI services from AAM cows and 1,042 AI services from TAI cows equipped with the Smarttag Neck (Nedap Livestock Management) from a dairy farm in Slovakia (farm 1). In the second experiment, 6,517 AI services from AAM cows and 1,226 AI services from TAI cows fitted with Heatime (Heatime Pro; SCR Engineers Ltd.) from 8 dairy farms in Germany (farms 2-9) were included. Pregnancy diagnosis was performed on a weekly basis by transrectal ultrasound (farms 1, 3, 7, 8) or by transrectal palpation (farms 2, 4-6, 9). Estrous intensity was represented by the peak value of the change in activity. In experiment 1, PA was categorized into low (x-factor 0-20) and high (x-factor 21-100) PA, and in experiment 2 into low (activity change = 35-89) and high (activity change = 90-100) PA. In TAI cows from both experiments, PA was additionally categorized into cows with no AAM alert. Data were analyzed separately for AAM and TAI cows using multinomial logistic regression models for PA in TAI cows and logistic regression models for PA in AAM cows and P/AI in both groups. In experiment 1, P/AI of AAM cows was greater for AI services performed with conventional frozen semen (57.6%) compared with sexed semen (47.2%), whereas type of semen only tended to be associated with P/AI in TAI cows (54.4% conventional frozen semen vs. 48.9% sexed semen). In experiment 2, P/AI was greater for fresh semen (AAM cows: 44.4% vs. TAI cows: 44.2%) compared with conventional frozen semen (AAM cows: 37.6% vs. TAI cows: 34.6%). In both experiments, pregnancy outcomes were associated with PA. In experiment 1, AAM cows with high PA (55.1%) had greater P/AI than cows with low PA (49.8%). Within TAI cows, cows with no alert (38.8%) had reduced P/AI compared with cows with low (54.2%) or high PA (61.8%). In experiment 2, AAM cows with high PA (45.8%) had greater P/AI compared with cows with low PA (36.4%). Timed AI cows with no alert (27.4%) had decreased P/AI compared with cows with low (41.1%) or high (50.8%) PA. The greatest risk factors for high PA were parity (experiment 1) and season of AI (except for TAI cows from experiment 1). We conclude that high PA at the time of AI is associated with greater odds of pregnancy for both AAM and TAI cows. In both experiments, about 2 thirds of AAM cows (experiment 1: 69.9% and experiment 2: 70.7%) reached high PA, whereas only approximately one-third or less of TAI cows (experiment 1: 37.3% and experiment 2: 23.6%) showed high PA. Although we observed similar results using 2 different AAM systems for the most part, risk factors for high PA might differ between farms and insemination type (i.e., AAM vs. TAI).

Evaluation of the diagnostic accuracy of a point-of-care device to measure concentrations of nonesterified fatty acids in serum and whole blood

The objective of this study was to compare measurements of nonesterified fatty acids (NEFA) between the gold standard diagnostic laboratory method and a handheld NEFA meter (Qucare Pro meter, DFI Co. Ltd.). Three experiments were conducted to study the usability of the meter. In experiment 1 we compared results of the meter obtained from measurements in serum and whole blood with results of the gold standard method. Based on the results of experiment 1 we compared the results measured by the meter in whole blood with results obtained from the gold standard method on a larger scale, as we wanted to omit the step of centrifugation with the cow-side test. In experiment 3 we determined the influence of ambient temperature on measurements. Overall, blood samples of 231 cows were collected between 14 and 20 d in milk. The Spearman correlation coefficients (ρ) were calculated and Bland-Altman plots were created to compare the accuracy of the NEFA meter with the gold standard. In addition, in experiment 2 receiver operating characteristic (ROC) curve analyses were performed, to define thresholds for the NEFA meter to detect cows with a NEFA concentration above 0.3, 0.4, and 0.7 mEq/L. In experiment 1, there was a high correlation between NEFA concentrations in whole blood and serum determined by the NEFA meter and the gold standard (ρ = 0.90 for measurement in whole blood; ρ = 0.93 for measurement in serum). In experiment 2, the measurement in whole blood with the NEFA meter was compared with the gold standard. Despite a lower correlation (ρ = 0.79) the ROC curve analyses revealed a high specificity and a moderate sensitivity for lower cut-points (i.e., 0.3 and 0.4 mEq/L). The NEFA meter underestimated especially high concentration of >0.7 mEq/L. Considering thresholds of 0.3, 0.4, and 0.7 mEq/L measured by the gold standard test, sensitivity and specificity were 59.1% and 96.7%, 79.0% and 95.4%, and 86.4% and 95.6%, respectively, when using 0.3, 0.3, and 0.4 mEq/L as thresholds for the NEFA meter. Accuracy was 74.1%, 88.3%, and 93.8% for the 3 thresholds tested. Experiment 3 showed that measurements should be conducted at approximately 21°C (ρ = 0.73) as correlations were poor at 6.2°C and 15.1°C (ρ = 0.18 and 0.22, respectively).

Associations between time in the close-up group and milk yield, milk components, reproductive performance, and culling of Holstein dairy cows fed acidogenic diets: A multisite study

The objective of this prospective cohort study was to evaluate the association between the prepartum days in the close-up group (DINCU) and milk yield, milk components, reproductive performance, and culling risk in the subsequent lactation for Holstein dairy cows. Dry cow feeding management of 20 farms was evaluated during 2 farm visits. All farms were feeding an acidogenic diet in the close-up group. Data from 14,843 cows were collected for 365 d following the second farm visit. Data sets of 13,314 cows were available for final statistical analysis after exclusion of cows with missing information about gestation length, cows with a gestation length shorter than 262 d or longer than 292, cows with 0 DINCU, and cows with >42 DINCU. At enrollment, 3,871 and 9,443 of those animals were nulliparous and parous cows, respectively. Continuous data such as energy corrected milk (ECM), the ratio of fat and protein, and somatic cell score (SCS) at first test day were analyzed using linear mixed models. Binary data such as stillbirth, culling within 60 DIM, and pregnancy within 150 DIM were analyzed using logistic regression models. Based on their different physiology, separate models were built for nulliparous and parous cows. All results displayed are the predicted least squares means from the multivariable analyses. A significant association between DINCU and milk yield at first test day was observed for nulliparous and parous cows. Nulliparous cows with 7, 21, or 35 DINCU had a first test day ECM of 31.8, 33.3, and 35.5 kg, respectively. Parous cows with 7, 21, or 35 DINCU had a first test day ECM of 42.8, 45.6, and 44.6 kg of ECM, respectively. In nulliparous cows, there was a tendency for an association between DINCU and the ratio of fat and protein at first test day. In parous cows, however, a significant association was observed. Parous cows with 7, 21, or 35 DINCU had a ratio of fat and protein of 1.31, 1.35, and 1.37, respectively. There was a significant association between DINCU and SCS at first test day in nulliparous and parous cows. In nulliparous cows with 7, 21, or 35 DINCU, SCS was 2.39, 2.49, and 2.85, respectively. In parous cows with 7, 21, or 35 DINCU, SCS was 2.46, 2.53, and 2.78, respectively. No associations were observed between DINCU and occurrence of stillbirth and DINCU and the risk of pregnancy within 150 DIM. The multivariable model predicted a tendency for an association between DINCU and the risk of being culled within 60 DIM in parous cows. Particularly, 0 to 6 DINCU were associated with a substantially increased risk of being culled. In conclusion, a short stay in the close-up group should be avoided to improve milk yield at first test day and to minimize culling risk for parous cows. A long stay in the close-up group (>30 d) was associated with reduced milk production and an increased ratio of fat and protein in milk of parous cows and increased SCS of nulliparous and parous cows.

Effects of a single transdermal administration of flunixin meglumine in early postpartum Holstein Friesian dairy cows: Part 1. Inflammatory and metabolic markers, uterine health, and indicators of pain

The objectives of this study were to assess the effects of a single transdermal administration of flunixin meglumine (FM) in early postpartum Holstein Friesian dairy cows on serum concentrations of inflammatory and metabolic markers, uterine health, and indicators of pain. The hypothesis was that the anti-inflammatory, antipyretic, and analgetic effects of the pharmaceutic agent would reduce systemic inflammation, resulting in improved metabolic and inflammatory profile, diminished incidence of metritis, and reduced expression of pain. A total of 500 cows (153 primiparous, 347 multiparous) from 3 different commercial dairy farms in the northeast of Germany were included in a randomized controlled clinical trial. Farms were preselected based on high haptoglobin concentrations in their fresh lactating cows. Cows were excluded if they had experienced dystocia, stillbirth, or twin birth, or if they showed any signs of milk fever, retained fetal membranes, or fever (>40°C). The cows were treated once with either FM (3.33 mg/kg) or a placebo as control (CON) through transdermal administration between 24 to 36 h postpartum (d 2). General health examinations were performed (daily from d 2-8 and additionally on d 15 postpartum), vaginal discharge was assessed using the Metricheck device (d 8 and 15 postpartum) and serum samples were analyzed for inflammatory and metabolic markers (d 2, 4, and 6 postpartum). Effects of treatment, parity, sampling day, and their interactions were evaluated using mixed effects models. Primiparous cows treated with FM showed lower serum haptoglobin concentrations (0.90 ± 0.08 vs. 1.17 ± 0.07 g/L; ± standard error of the mean) and higher serum albumin concentrations (35.5 ± 0.31 vs. 34.8 ± 0.31 g/L) on d 6 postpartum. They also had a lower risk for purulent vaginal discharge with or without a fever compared with CON cows on d 15 postpartum (odds ratio for CON vs. FM: 1.63, 95% CI: 1.26-2.00), and body temperature was lower throughout the first 15 d in milk (39.1 ± 0.11 vs. 39.2 ± 0.11°C). Multiparous cows treated with FM had lower serum β-hydroxybutyrate concentrations on d 4 postpartum (0.71 ± 0.05 vs. 0.78 ± 0.05 mmol/L) and d 6 postpartum (0.74 ± 0.05 vs. 0.80 ± 0.05 mmol/L). Regardless of parity, FM-treated cows were significantly less likely to abduct their tail from their body (14.3 vs. 23.6%) and show an arched back (27.9 vs. 39.7%) on the day after treatment compared with CON cows. It can be concluded that FM treatment slightly reduced inflammation and diminished the risk for metritis in primiparous cows, improved metabolic profile in multiparous cows, and reduced expressions of pain in all cows.

Randomized clinical trial to evaluate the effects of a prepartum cholecalciferol injection on postpartum serum calcium dynamics and health and performance in early-lactation multiparous dairy cows

The objectives of the present study were (1) to evaluate the effect of prepartum cholecalciferol treatment on serum Ca concentration during the first 10 d after calving and (2) to evaluate the effect of treatment on subsequent health and performance. Multiparous Holstein cows (n = 377) from one dairy farm were fed a negative dietary cation-anion difference diet (-31 mEq/kg of DM) for the last 21 d of gestation. On d 275, the animals were randomly assigned to a control or a treatment group. Cows in the control group were left untreated, and cows in the treatment group received an injection of 12 × 10⁶ IU of cholecalciferol intramuscularly on the day of enrollment. If treated cows did not deliver the calf within 6 d, they were reinjected with 10 × 10⁶ IU of cholecalciferol. Blood samples were drawn on 1, 2, 3, 5, 7, and 10 days in milk (DIM) and analyzed for serum Ca, P, and Mg concentrations. In a subsample of cows (50 control cows, 35 cows treated once with cholecalciferol, and 15 cows treated twice) serum haptoglobin, nonesterified fatty acids, β-hydroxybutyrate, and 25-hydroxycholecalciferol concentrations were analyzed on 1, 5, and 10 DIM. Binary data [retained placenta (RP), metritis] were analyzed using logistic regression models. Repeated measures ANOVA with first-order autoregressive covariance was performed to evaluate the treatment effect on milk yield over the first 10 test days after parturition, 25-hydroxycholecalciferol, serum Ca, P, Mg, β-hydroxybutyrate, nonesterified fatty acids, and haptoglobin concentrations. Cox proportional hazards were used to model the time to event outcomes (time to pregnancy within 200 d, culling until 300 DIM). After enrollment of 31.4% of cows and a preliminary analysis, adverse reactions became apparent, and the study was stopped. Cows treated with cholecalciferol had a greater risk of incurring RP and metritis. The adjusted mean incidences were 2.0%, 7.7%, and 4.0% for RP, and 21.6%, 39.3%, and 33.3% for metritis for control cows, cows treated once, and cows treated twice with cholecalciferol, respectively. Compared with control cows, cows injected once with 12 × 10⁶ IU of cholecalciferol produced less energy-corrected milk on the first (-3.76 kg) and second (-2.75 kg) test days, respectively. Cows injected twice with cholecalciferol (12 × 10⁶ IU of cholecalciferol and 10 × 10⁶ IU 1 wk later) had a reduced milk yield only at first test day (-3.80 kg). Treatment with cholecalciferol led to a significant increase in 25-hydroxycholecalciferol on d 1, 5, and 10 after calving. Serum Ca and P concentrations were significantly increased in cows treated with cholecalciferol, but serum Mg concentrations were significantly reduced. Haptoglobin concentrations were significantly increased on 5 DIM in cows injected once with 12 × 10⁶ IU of cholecalciferol. Although we observed no effect of treatment on culling until 300 DIM, time to pregnancy was delayed by 34 d in cows injected once with 12 × 10⁶ IU of cholecalciferol. In the present study, injection with 12 × 10⁶ IU of cholecalciferol had detrimental effects on health and milk production despite the beneficial effects on Ca homeostasis.

Management-related factors in dry cows and their associations with colostrum quantity and quality on a large commercial dairy farm

The objective of this observational study was to evaluate the association of management-related factors in dry cows and colostrum quantity and quality in Holstein cows on a large commercial dairy farm. This study was conducted from January 2018 to December 2020 on a commercial dairy farm in Germany, milking approximately 2,500 Holstein cows. Dairy personnel recorded colostrum quantity (n = 7,562) and evaluated colostrum quality in a subsample of animals (n = 2,600) using a digital Brix refractometer. Generalized linear mixed models were constructed to evaluate the association of management-related factors and colostrum quantity and quality. Models were run separately for primiparous or multiparous cows. The outcome variable was either colostrum quantity (kg) or quality (% Brix). Average colostrum quantity was 4.0 ± 2.5 kg, 5.1 ± 3.4 kg, and 5.5 ± 3.5 kg for cows in lactation 1, 2, and ≥3, respectively. In primiparous cows (n = 2,351), colostrum quantity was affected by month of calving (greatest in April = 4.1 kg, and lowest in November = 3.2 kg), sex of the calf (female singleton = 3.50 ± 0.26 kg; male singleton = 3.76 ± 0.27 kg; twins = 2.97 ± 0.66 kg), stillbirth (stillbirth = 3.14 ± 0.39 kg; no stillbirth = 3.68 ± 0.31 kg). In multiparous cows (n = 5,216), colostrum quantity was affected by month of calving (greatest in May = 5.5 kg, and lowest in October = 3.8 kg), calving ease (calving ease 0 = 4.23 ± 0.26 kg; score 1 = 4.77 ± 0.21 kg; score 2 = 4.98 ± 0.22 kg; score 3 = 5.30 ± 0.22 kg), sex of the calf (female singleton = 4.42 ± 0.21 kg; male singleton = 5.00 ± 0.21 kg; twins = 5.03 ± 0.30 kg), stillbirth (stillbirth = 4.24 ± 0.38 kg; no stillbirth = 5.39 ± 0.11 kg), milk yield in previous lactation (+0.1 kg increase for 1,000 kg more milk yield in previous lactation), days spent in the far-off group (0.05 ± 0.003 kg for every day), and days in the close-up pen (0.06 ± 0.010 kg for every day). Average colostrum quality was 25.1 ± 3.4% Brix, 24.7 ± 3.3% Brix, and 27.6 ± 4.4% Brix for cows in lactation 1, 2, and ≥3, respectively. In primiparous cows (n = 817), colostrum quality was affected only by month of calving. Colostrum quality in primiparous cows was greatest in December (26.8% Brix) and lowest in August (23.9% Brix). In multiparous cows (n = 1,783), colostrum quality was affected by parity (lactation 2 = 25.2 ± 2.7% Brix; lactation 3+ = 27.9 ± 2.7% Brix), month of calving (greatest in February = 27.5% Brix, and lowest in August = 25.7% Brix), milk yield in previous lactation, and colostrum quantity. We observed a seasonal pattern for colostrum quantity and quality. Future intervention studies using multiple farms need to elucidate whether management of the photoperiod or length of exposure to close-up diets, or both, can help to optimize colostrum production.

Occurrence and greater intensity of estrus in recipient lactating dairy cows improve pregnancy per embryo transfer

The aim of this study was to determine the association between occurrence and intensity of estrous expression with pregnancy success in recipient lactating dairy cows subjected to embryo transfer (ET). Two observational studies were conducted. Holstein cows were synchronized using the same timed ET protocol, based on estradiol and progesterone in both experiments. At 9 d after the end of the timed ET protocol only animals that had ovulated were implanted with a 7-d embryo [experiment 1 (Exp. 1); n = 1,401 ET events from 1,045 cows, and experiment 2 (Exp. 2); n = 1,147 ET events from 657 cows]. Embryos were produced in vivo (Exp. 1 and Exp. 2) and in vitro (only Exp. 2), then transferred to recipient cows as fresh or frozen-thawed. Pregnancy was confirmed at 29 and 58 d after the end of timed ET protocol. In Exp. 1, animals had their estrous expression monitored through a tail chalk applied on the tail head of the cows and evaluated daily for chalk removal (no estrus: 100% of chalk remaining; estrus: <50% of chalk remaining). In Exp. 2, cows were continuously monitored by a leg-mounted automated activity monitor. Estrous expression was quantified using the relative increase in physical activity at estrus in relation to the days before estrus. Estrous expression was classified as no estrus [<100% relative increase in activity (RI)], weak intensity (100-299% RI), and strong intensity (≥300% RI). Data were analyzed by analysis of variance using mixed linear regression models (GLIMMIX) in SAS (SAS Institute Inc.). A total of 65.2% (914/1,401) and 89.2% (1,019/1,142) of cows from Exp. 1 and Exp. 2, respectively, displayed estrus at the end of the ovulation synchronization protocol. In Exp. 1, cows expressing estrus before to ET had greater pregnancy per ET than those that did not [41.0 ± 2.3% (381/914) vs. 31.5 ± 2.9% (151/487), respectively]. Similarly, in Exp. 2, cows classified in the strong intensity group had greater pregnancy per ET compared with cows in the weak intensity and no estrus groups [41.3 ± 2.2% (213/571) vs. 32.7 ± 2.7% (115/353) vs. 11.3 ± 3.5% (26/218), respectively]. There was no effect of ET type on pregnancy per ET in Exp. 1. However, in Exp. 2, cows that received an in vivo-produced embryo, either fresh or frozen, had greater pregnancy per ET compared with cows that received in vitro-produced embryo. Cows receiving embryos in the early blastocyst and blastocyst stage had greater fertility compared with cows receiving embryos in the morula stage. There was an interaction between the occurrence of estrus and the stage of embryo development on pregnancy per ET, cows which displayed estrus and received a morula or early blastocyst had greater pregnancy per ET than cows that did not display estrus. In conclusion, the occurrence and the intensity of estrous expression improved pregnancy per ET in recipient lactating dairy cows and thus could be used as a tool to assist in the decision making of reproduction strategies in dairy farms.

Economic impact of adding a second prostaglandin F2α treatment during an Ovsynch protocol using a meta-analytical assessment and a stochastic simulation model

Incomplete luteal regression after treatment with a single dose of PGF_2α during an Ovsynch protocol decreases fertility to timed artificial insemination (AI). An additional treatment with PGF_2α 24 h after the first dose has been recommended to increase the proportion of cows with complete luteal regression and subsequent pregnancy per AI (P/AI). This is, however, associated with additional costs of labor and product. The objective was to develop a stochastic partial budget model to estimate the economic impact of an additional PGF_2α treatment on d 8 during an Ovsynch protocol in primiparous and multiparous cows. A systematic review of the literature and a meta-analytical assessment was performed to evaluate the effects of adding a second PGF_2α treatment during the Ovsynch protocol on P/AI in lactating dairy cows. Thirteen randomized controlled experiments from 11 published manuscripts including 9,735 cows were used. We were able to retrieve information regarding parity from 9 experiments from 7 manuscripts (2,367 primiparous cows and 5,356 multiparous cows). An additional dose of PGF_2α yielded a 5.60 risk difference in P/AI [95% confidence interval (CI) = 3.69-7.52]. In primiparous cows and multiparous cows, an additional dose of PGF_2α yielded a 4.24 (95% CI = 0.31-8.17) and a 5.31 risk difference in P/AI (95% CI = 2.75-7.87). Revenue was based on the associated improvement in reproductive performance because of an increase in P/AI multiplied by the value of a pregnancy (PGVAL). Median PGVAL was €252, ranging from €42 (fifth percentile) to €623 (95th percentile). Based on parity, median PGVAL was €205 (5th percentile = €43; 95th percentile = €651) and €264 (5th percentile = €88; 95th percentile = €598) for primiparous (n = 1,252) and multiparous cows (n = 3,003), respectively. Using a stochastic simulation model with 10,000 iterations, adding a second PGF_2α dose on d 8 was more profitable (€7.76/cow; 5th percentile = €0.01; 95th percentile = €29.40) compared with a single PGF_2α administration on d 7. In primiparous cows, adding a second PGF_2α treatment was more profitable (€1.99/cow; 5th percentile = -€3.08; 95th percentile = €22.52) in 67% of all simulated iterations. In multiparous cows, adding a second PGF_2α treatment was more profitable (€7.92/cow; 5th percentile = -€0.09; 95th percentile = €28.22) in 95% of all simulated iterations. In conclusion, there was a clear benefit of an additional PGF_2α treatment during the Ovsynch protocol on P/AI (+5.6 percentage units). Despite additional costs for hormones and labor, an additional treatment with PGF_2α on d 8 was more profitable in 95% of all scenarios because of the associated increase in fertility. It turned out, however, that adding a second PGF_2α treatment was more profitable in multiparous cows compared with primiparous cows.

Association of estrous expression detected by an automated activity monitoring system within 40 days in milk and reproductive performance of lactating Holstein cows

The objective of this observational study was to evaluate the association of estrous expression within 40 days in milk (DIM) using a neck-mounted automated activity monitor (Heatime Pro; SCR Engineers Ltd.) with reproductive performance in lactating Holstein cows. A total of 2,077 cows (614 primiparous cows and 1,463 multiparous cows) from 5 commercial dairy farms were included in the statistical analyses. Activity data from the first 7 d after calving were excluded. An estrus event was defined as an activity change index ≥35 for more than 2 h. Cows were classified according to the number of estrus events from d 7 until d 40 postpartum into 3 categories: (1) no estrus event (Estrus0); (2) one estrus event (Estrus1), and (3) 2 or more estrus events (Estrus2). Generalized linear mixed models were used to analyze continuous and categorical data. Shared frailty models were used for time to event data. Overall, 52.7% of cows had no estrus event detected by an automated activity monitor system from d 7 until d 40 postpartum. Herd level prevalence of Estrus0 ranged from 37.5 to 58.4%. Estrous expression from d 7 until d 40 postpartum affected estrous duration and estrous intensity at first artificial insemination (AI). Cows in Estrus0 had the shortest duration (13.2 ± 0.33 h) compared with cows in Estrus1 (13.8 ± 0.36 h) and Estrus2 (14.8 ± 0.41 h). Cows in Estrus2 had a longer estrous duration at first postpartum AI compared with cows in Estrus1. Among Estrus0 cows, 46.2% had an estrus event with high intensity at first postpartum AI. Among cows in Estrus1 and Estrus2, 50.8 and 53.8% had an estrus event with high intensity at first postpartum AI, respectively. There was a significant difference between Estrus2 and Estrus0 and a tendency between Estrus0 and Estrus1. There was no difference between Estrus1 and Estrus2. For Estrus0, Estrus1, and Estrus2 cows, pregnancy per AI was 29.4, 30.9, and 37.8%, respectively. There was a significant difference between Estrus0 and Estrus2 and Estrus1 and Estrus2. There was no difference between Estrus0 and Estrus1. Estrous expression from d 7 until d 40 postpartum affected time to first AI and time to pregnancy. Compared with Estrus0 cows, cows in Estrus1 [hazard risk (HR) = 1.74] and Estrus2 (HR = 1.77) had an increased hazard of being inseminated within 100 DIM. There was no difference between Estrus1 and Estrus2. Median DIM to first AI were 70, 59, and 58 for cows in Estrus0, Estrus1, and Estrus2, respectively. Compared with Estrus0 cows, cows in Estrus1 (HR = 1.28) and Estrus2 (HR = 1.33) had an increased hazard of becoming pregnant within 200 DIM. There was no difference between Estrus1 and Estrus2. Median DIM to pregnancy were 127, 112, and 103 for Estrus0 cows, Estrus1 and Estrus2, respectively. In conclusion, cows with no estrous expression from 7 to 40 DIM had reduced estrous expression at first AI and inferior reproductive performance compared with cows that displayed estrous activity.

Factors associated with estrous expression and subsequent fertility in lactating dairy cows using automated activity monitoring

The objective of this observational study was to identify factors associated with estrous duration (DU) and intensity measured as the peak of activity (PA) change and subsequent fertility in lactating Holstein cows using a neck-mounted automated activity monitor (Heatime Pro, SCR Engineers Ltd., Netanya, Israel). Ambient temperature and relative humidity were recorded hourly to calculate the temperature-humidity index (THI). A total of 5,933 estrus events from 3,132 cows located on 8 commercial dairy farms in Germany were used for this study. Farms participated in monthly DHIA testing. Pregnancy diagnosis was performed either by transrectal palpation [farm 1: 42 ± 3 d; farm 3: 40 ± 3 d; farms 4 and 8: 38 ± 3 d; farm 5: 43 ± 3 d after artificial insemination (AI)] or transrectal ultrasonography (farms 2, 6, and 7: 30 ± 3 d after AI). Estrous intensity was categorized based on peak activity of estrus into low (35-89 index value), and high (90-100 index value) PA. Overall, 73.5% of estrus events were of high PA. The mean (± standard error of the mean) DU was 14.94 ± 0.06 h. There was a strong correlation between DU and PA (r = 0.67). In the final statistical model, only PA was associated with pregnancy per artificial insemination (P/AI), with 1.35 greater odds of pregnancy for cows with high PA compared with cows with low PA. Increased THI 1 wk before AI was associated with shorter DU, lower PA, and decreased P/AI. A small percentage of cows (4.7%) showed short interestrus intervals (i.e., more than 1 activity peak within 7 d close to the event of estrus), resulting in reduced DU, PA, and P/AI. The change of weighted rumination was associated with DU and PA, as a lower nadir was associated with a greater risk for high PA and long DU. There was no association, however, between the nadir of change of weighted rumination and P/AI. Whereas milk yield and somatic cell count from the DHIA test date before AI were negatively associated with estrous expression, neither milk yield nor somatic cell count was associated with P/AI. Surprisingly, multiparous cows expressed estrus with longer DU (13.15 ± 0.31 h) compared with primiparous cows (12.52 ± 0.32 h), whereas PA did not differ among parities. Pregnancy per AI was greater for primiparous (29.4%) than for multiparous (22.1%) cows. An estrus event with long DU or high PA was more likely later in lactation. Milk fat, milk protein, milk urea nitrogen, and lactose from the DHIA test date closest to AI had no association with estrous expression or P/AI. In conclusion, DU and PA were highly correlated, and cows with high PA were particularly associated with greater odds for pregnancy. A negative association between estrous expression and P/AI was identified for increased THI 1 wk before AI and cows with short interestrus intervals using automated activity monitor.

Timing of artificial insemination using fresh or frozen semen after automated activity monitoring of estrus in lactating dairy cows

The objective of this observational experiment was to determine the association between the time of artificial insemination (AI) and pregnancy per AI (P/AI) in lactating Holstein cows inseminated with either fresh or frozen semen considering different characteristics of an estrus event (i.e., onset, peak, and end) using an automated activity monitoring system. A total of 3,607 AI services based on the alert of an automated activity monitoring system (Heatime; SCR Engineers Ltd., Netanya, Israel) were evaluated from 4 commercial dairy farms in Germany. Pregnancy diagnosis was performed by transrectal palpation 38 ± 3 d after AI or by transrectal ultrasonography 30 ± 3 d after AI. Estrus intensity was categorized based on peak activity of estrus (PAE) into low (35-89 index value) and high (90-100 index value) intensity. The mean (± standard deviation) duration of an estrus event was 14.3 ± 4.6 h. The mean (± standard deviation) interval from onset of estrus (OE; moment where index value was ≥35) to AI was 16.8 ± 8.0 h, from PAE to AI was 11.9 ± 8.1 h, and from end of estrus (EE; moment where index value returned to <35) to AI was 2.5 ± 8.7 h. Primiparous cows had greater P/AI than multiparous cows, whereas first AI postpartum yielded greater P/AI compared with subsequent AI services. Type of semen was not associated with P/AI. Cows with heat stress 1 wk before AI had decreased P/AI. Cows with low estrus intensity (26.0%) were less fertile compared with cows showing high estrus intensity (32.8%). Cows with intermediate 100-d milk yield had decreased P/AI compared with cows with either low or high 100-d milk yield. There was a quadratic effect of the interval from OE to AI on P/AI. At 38 d after AI, P/AI was greatest for cows inseminated from 7 to 24 h after OE, within 18 h after PAE, or from 5 h before EE to 12 h after EE. There was no interaction between the interval from OE to AI and type of semen. There tended to be an interaction between the intervals from PAE to AI and type of semen and from EE to AI and type of semen. Cows inseminated with fresh semen within 5 h before EE had greater P/AI compared with frozen semen, whereas cows inseminated with frozen semen from 13 to 18 h after EE had greater P/AI compared with fresh semen. In conclusion, inseminating cows from 7 to 24 h after OE or 1 to 18 h after PAE yielded greatest P/AI irrespective of type of semen. In addition, high estrus intensity was positively associated with P/AI.

Effect of dose and timing of prostaglandin F2α treatments during a 7-d Ovsynch protocol on progesterone concentration at the end of the protocol and pregnancy outcomes in lactating Holstein cows

The objective of this study was to evaluate the effect of two prostaglandin F_2α (PGF) treatments 24 h apart (500 μg of cloprostenol) and treatment with a double PGF dose on d 7 (1000 μg of cloprostenol) during a 7-d Ovsynch protocol on progesterone (P4) concentration and pregnancy per artificial insemination (P/AI) in lactating Holstein cows. We hypothesized that treatment leads to a decreased P4 concentration at the second GnRH treatment (G2) and an increase in P/AI compared to the traditional 7-d Ovsynch protocol. A secondary hypothesis was that the treatment effect is influenced by the presence of a corpus luteum (CL) at the first GnRH treatment (G1). Two experiments were conducted on 8 commercial dairy farms in Germany. Once a week, cows from both experiments were assigned in a consecutive manner to receive: (1) Ovsynch (control: GnRH; 7 d, PGF; 9 d, GnRH), (2) Ovsynch with a double PGF dose (GDPG: GnRH; 7 d, 2xPGF; 9 d, GnRH), or (3) Ovsynch with a second PGF treatment 24 h later (GPPG: GnRH; 7 d, PGF; 8 d, PGF; 32 h, GnRH). All cows received timed AI (TAI) approximately 16 h after G2. Pregnancy diagnosis was performed by transrectal palpation (38 ± 3 d after TAI, experiment 1) or transrectal ultrasonography (35 ± 7 d after TAI, experiment 2). Whereas farms from experiment 1 used a Presynch-Ovsynch protocol (PGF, 14 d later PGF, 12 d later GnRH, 7 d later PGF, 2 d later GnRH, and 16-18 h later TAI) to facilitate first postpartum TAI, no presynchronization protocol was used on farms from experiment 2. In experiment 1, we enrolled 1581 lactating dairy cows (60 experimental units) from 2 dairy farms. At G2, blood samples were collected from a subsample of cows (n = 491; 16 experimental units) to determine P4 concentration at G2. In experiment 2, we enrolled 1979 lactating dairy cows (252 experimental units) from 6 dairy farms. Transrectal ultrasonography was performed to determine the presence or absence of a CL at G1. In experiment 1, treatment affected P/AI (P = 0.01) and P/AI was greater for GDPG (38.2%) and GPPG (38.9%) than for control cows (29.8%). Both, GDPG and GPPG cows had decreased P4 concentration at G2 compared with control cows (P < 0.01). Whereas both treatments increased the percentage of cows with very low P4 concentration (0.00-0.09 ng/mL) at G2, only the GPPG treatment decreased the percentage of cows with high P4 concentration (≥0.6 ng/mL) at G2 compared to the control group. In experiment 2, P/AI was greater for GPPG (37.4%) than for control cows (31.0%; P = 0.03) and tended to be greater than for GDPG cows (31.8%; P = 0.05). Cows from the GDPG group had similar (P = 0.77) P/AI compared to the control group. Pregnancy per AI did not differ between cows with a CL at G1 and cows without a CL at G1 (34.1% vs. 32.6%; P = 0.50). There was no interaction between treatment and presence of a CL at G1 on P/AI (P = 0.61). Combining data from the 2 experiments but excluding cows from experiment 1 receiving presynchronization before first TAI (n = 2573; 312 experimental units), P/AI was greater for GPPG (40.3%; P < 0.01) than for control (31.8%) and GDPG cows (33.4%). Between GDPG and control cows, P/AI did not differ (P = 0.46). We conclude that overall the addition of a second PGF treatment on d 8 during a 7-d Ovsynch protocol increased P/AI compared to the traditional 7-d Ovsynch including a single PGF dose on d 7 and to a double PGF dose on d 7. Doubling the PGF dose on d 7 in a 7-d Ovsynch protocol did not affect P/AI. Use of a presynchronization protocol, however, seems to influence the effect of a dose frequency modification of PGF treatment in an Ovsynch protocol. Presynchronized cows receiving first postpartum TAI had similarly increased P/AI treated with a double PGF dose compared with treatment with a second PGF dose. Future studies need to elucidate whether the treatment effect is modified by presynchronization of the first postpartum TAI.

Association between serum calcium dynamics around parturition and common postpartum diseases in dairy cows

The objective of this study was to compare periparturient serum Ca dynamics (CaDyn) in cows with and without diseases in early lactation. The study enrolled 1,949 cows from a commercial dairy farm in northern Germany. Blood samples were drawn 7 d before expected calving date and on d 0, 1, 3, and 7 after calving and analyzed for serum Ca concentration. Cows were monitored for clinical hypocalcemia (CH), ketosis, left displaced abomasum (LDA), retained placenta, acute puerperal metritis (APM), mastitis, and pneumonia. To evaluate the association between CaDyn and diseases during the transition period, repeated measures ANOVA with first-order autoregressive covariance were performed. Serum CaDyn of healthy cows (i.e., without any of the aforementioned diseases) was compared with CaDyn of cows with one of the aforementioned diseases (CH, ketosis, APM, mastitis, LDA, and pneumonia), and cows with multiple diseases (CH+, ketosis+, APM+, mastitis+, LDA+, and pneumonia+). Separate models were built for primiparous and multiparous cows. For primiparous cows, we evaluated the association between CaDyn and ketosis (healthy cows vs. cows with ketosis vs. cows with ketosis+) and CaDyn and APM (healthy cows vs. cows with APM vs. cows with APM+). The same models were built for multiparous cows. Three additional models were built for multiparous cows to evaluate the association between CaDyn and CH (healthy cows vs. cows with CH vs. cows with CH+), mastitis (healthy cows vs. cows with mastitis vs. cows with mastitis+), or LDA (healthy cows vs. cows with LDA vs. cows with LDA+). In primiparous cows, serum Ca concentrations of cows with ketosis, APM, and APM+ were significantly reduced on d 3 and 7 after calving, compared with healthy cows. Serum Ca concentrations of primiparous cows with ketosis+ were reduced on d 3, but not on d 7 after calving. Multiparous cows with CH had significantly reduced serum Ca concentrations on d 0, 1, and 3 compared with healthy cows. On d 3 and 7, serum Ca concentration of CH+ cows was significantly reduced compared with healthy multiparous cows. Multiparous cows with ketosis and ketosis+ had significantly reduced serum Ca concentrations on d 1 and 3 compared with healthy cows. Cows with APM+ had significantly increased serum Ca concentrations on d 0 and reduced serum Ca concentrations on d 3, compared with healthy cows. Whereas multiparous cows with mastitis had a reduced serum Ca concentration on d 1, mastitis+ cows had a reduced serum Ca concentration on d 1 and 3, compared with healthy multiparous cows. Overall, multiparous cows with LDA+ had reduced serum Ca concentrations. Especially a delayed onset of hypocalcemia (d 3 and 7) was indicative for the development of disease in primiparous cows. In multiparous cows, reduced serum Ca concentrations on d 1 and 3 were associated with occurrence of diseases. Future studies should evaluate whether reduced serum Ca concentrations are a cause or concomitant circumstance of diseases in early lactation.

Evaluation of different analytical methods to assess failure of passive transfer in neonatal calves

The objective of this study was to evaluate different analytical methods of assessing failure of passive transfer (FPT) in neonatal calves. We hypothesized that 3 different media (i.e., centrifuged serum, centrifuged plasma, filtered plasma) and different analytical methods [i.e., ELISA, capillary electrophoresis (CE), Brix refractometer, and handheld optical refractometer] would be highly correlated with the gold standard radial immunodiffusion (RID) and would generate comparable results. Serum and plasma blood samples were collected from Holstein Friesian calves (n = 216) aged 1 to 7 d, from 2 commercial dairy herds in northeast Germany. The RID analysis showed that 59 of 216 calves (27%) had serum IgG concentrations of <10 mg/mL and 157 calves (73%) had serum concentrations of ≥10 mg/mL. The mean IgG concentration (± standard deviation) was 17.1 ± 9.8 mg/mL, and the range was 0.8 to 47.8 mg/mL. In serum, the correlation between RID and CE was r = 0.97, and between RID and ELISA was r = 0.90; CE and ELISA were also highly correlated (r = 0.89). Both refractometry methods were highly correlated with RID using centrifuged serum, centrifuged plasma, or filtered plasma (Brix refractometer: r = 0.84, 0.80, and 0.78, respectively; handheld optical refractometer: r = 0.83, 0.81, and 0.80, respectively). We determined test characteristics (optimum thresholds, sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve) for CE, ELISA, and the handheld optical and digital refractometers using receiver operating characteristic curve analyses with RID as the reference value. Optimal thresholds for assessing FPT using plasma were higher than for serum, regardless of the method of plasma harvesting. The 4 different devices had comparable areas under the curve, irrespective of the medium used. All analytical methods can be used to assess FPT.

Evaluation of 2 different treatment procedures after calving to improve harvesting of high-quantity and high-quality colostrum

The objective of this study was to evaluate 2 different treatment procedures at the first milking after calving to increase colostrum quantity and to improve colostrum quality in dairy cows. We hypothesized that either exogenous treatment with oxytocin or the presence of the calf at first milking would lead to higher colostrum quantity and higher IgG concentration. The study was conducted from October to December 2017 on a commercial dairy farm in Germany. A total of 567 cows at the time of calving were enrolled, but for the final analyses only 521 animals were considered. The cows were randomly assigned on a daily basis into 1 of 3 groups: (1) control group (n = 177), (2) application of 20 IU of oxytocin i.m. (OXY; n = 163), and (3) presence of the calf (CA; n = 181) before and during milking. Cows in the control and oxytocin group had no contact with their calves after calving and were milked in a separate milking parlor. Cows in the oxytocin group were injected with 20 IU of oxytocin i.m. 3 min before manual stimulation. For cows in the third group, the calf was placed into a calf cart and located in front of the cow 3 min before manipulation of the cow. Colostrum quantity was determined by a digital hanging scale. The colostrum quality was assessed with digital Brix refractometry and ELISA. To evaluate the effect of 2 different treatment procedures, a generalized linear mixed model was constructed using SPSS (SPSS Inc., IBM, Ehningen, Germany). The mean (±SE) colostrum quantity was 4.17 ± 0.30 kg. The treatment procedures and the harvesting time after calving had no effect on colostrum quantity. Parity, calf birth weight, and calving time affected colostrum quantity. Cows in second parity had the lowest quantity of colostrum (3.74 ± 0.37 kg) compared with cows in parity 1 (4.75 ± 0.34 kg) and cows in parity 3 or greater (4.75 ± 0.38 kg). Cows calving during the night (2200 until 0600 h; 4.93 ± 0.37 kg) had the highest quantity of colostrum compared with cows calving in the morning (0600 until 1400 h; 4.17 ± 0.38 kg) or afternoon (1400 until 2200 h; 4.14 ± 0.34 kg). Regarding colostrum quality, 48% of the colostrum samples contained ≥50 mg of IgG/mL. The mean IgG concentration was 54.6 ± 2.80 mg of IgG/mL. Colostrum quality was affected by the treatment procedures, colostrum quantity, parity, calving time, harvesting time after calving, and the calving day during the week. Both treatment procedures (i.e., OXY with mean IgG concentration results of 57.0 mg of IgG/mL and CA with 56.0 mg of IgG/mL) resulted in higher IgG concentrations in colostrum compared with the control group (50.7 mg of IgG/mL). With increasing colostrum quantity, the colostrum quality decreased in primiparous and multiparous cows. A longer time lag between calving and milking negatively affected the colostrum quality. Concentration of IgG was higher for cows in parity 3 or greater (64.6 ± 2.59 mg of IgG/mL) compared with cows in parity 1 (48.5 ± 2.86 mg of IgG/mL) and cows in parity 2 (50.7 ± 2.89 mg of IgG/mL). Cows calving during the night had greater IgG concentrations (60.4 ± 2.92 mg of IgG/mL) compared with cows calving in the morning (51.9 ± 2.98 mg of IgG/mL) or afternoon (51.3 ± 2.71 mg of IgG/mL). Harvesting colostrum on quieter days, such as Sundays, resulted in higher IgG concentrations (61.4 ± 3.70 mg of IgG/mL). The assessment by Brix refractometry resulted in a mean result of 26.0 ± 0.20% Brix. Treatment procedures and the harvesting time after calving had no effect on colostrum quality. A negative association was observed between colostrum quantity and quality in primiparous and multiparous cows determined by Brix refractometry. Brix readings were greater for cows in parity 3 or higher (27.7 ± 0.26% Brix) compared with cows in parity 1 (25.3 ± 0.30% Brix) and cows in parity 2 (25.0 ± 0.32% Brix). In conclusion, the treatment procedure for the first milking is irrelevant to improve the quantity of colostrum. Both treatment procedures, however, increased IgG concentrations as determined by ELISA.

Serum calcium dynamics within the first 3 days in milk and the associated risk of acute puerperal metritis

The objectives of this study were to evaluate postpartum serum calcium dynamics for different parity groups of dairy cows and to assess whether serum calcium concentration on d 0, 1, and 3 postpartum was associated with the risk of developing acute puerperal metritis (APM). The study took place on a commercial dairy farm in northern Germany and included 4,043 Holstein dairy cows. Calving difficulties, such as dystocia, twins, or stillbirth, were recorded. Blood samples were obtained on d 0, 1, and 3 after calving for analysis of serum calcium concentration. Animals were examined daily for clinical symptoms of retained placenta, APM, mastitis, and displaced abomasum until 10 d in milk. To determine serum calcium dynamics postpartum, we performed repeated-measures ANOVA with first-order autoregressive covariance. A logistic regression model was used to evaluate the association of serum calcium concentration with the risk of developing metritis. Serum calcium concentration was affected by time relative to calving, parity, and APM. Increasing parity negatively affected serum calcium concentration on d 0 and 1. Serum calcium concentration reached its lowest level on d 1 and 3 in multiparous and primiparous cows, respectively. The concentration increased from d 1 to 3 in multiparous cows and decreased from d 0 to 3 in primiparous cows. The association of APM and serum calcium dynamics varied by parity. On d 3, serum calcium concentration was significantly lower in animals with subsequent APM than in those without APM. The overall incidence of APM was 12.0% (primiparous cows, 20.4%; multiparous cows, 8.6%). An association existed between serum calcium concentration on d 3 after calving and APM. Primiparous cows had an odds ratio of 0.12 for serum calcium concentration on d 3, indicating that a primiparous cow with serum calcium concentration of 2.5 mmol/L had a 88% lower chance of developing APM compared with a cow with a concentration of 1.5 mmol/L. Multiparous cows had an odds ratio of 0.34 for serum calcium concentration on d 3, indicating that a multiparous cow with serum calcium concentration of 2.5 mmol/L had a 66% lower chance of developing APM compared with a cow with a concentration of 1.5 mmol/L. Primiparous cows with low serum calcium concentration had the highest predicted probability of developing APM. Our results reveal a dynamic in serum calcium concentration in the first 3 d in milk. Consequently, the day of sampling and the observed risk period for hypocalcemia are important when conducting epidemiological studies to evaluate associations between hypocalcemia and clinical diseases.

Randomized clinical trial to evaluate the efficacy of prostaglandin F2α to treat purulent vaginal discharge in lactating dairy cows

The objectives of this study were (1) to assess the effect of purulent vaginal discharge (PVD) on reproductive performance using a 4-point vaginal discharge score (VDS) and (2) to evaluate the effect of PGF2α treatment in cows with PVD on reproductive performance. Holstein cows (n = 2,473) from 1 commercial dairy farm had their vaginal discharge scored at 32 ± 3 d in milk (DIM) using a 4-point scale. Cows were also scored for body condition score and had their ovaries examined using transrectal ultrasound. A VDS-2 or greater was used to define PVD. Cows with PVD were assigned to receive 2 doses of 500 µg of PGF2α analogue (n = 277; Cloprostenol; PGF Veyx forte, Veyx Pharma Ltd., Schwarzenborn, Germany) 14 d apart (odd ear tag number) or remained untreated (n = 272; even ear tag number). All cows not detected in estrus at 90 ± 3 DIM were enrolled into a timed artificial insemination (AI) protocol. The effect of VDS and the effect of PGF2α in cows with PVD on reproductive performance were evaluated separately. First service conception risk (FSCR), time to first AI, and time to pregnancy were used as indicators for reproductive performance. Data were analyzed with Cox's regression and mixed logistic models. The prevalence of PVD was 22.2% (548/2,473). We detected an interaction of parity and VDS for FSCR and time to pregnancy. In primiparous cows, VDS had no effect on FSCR and time to pregnancy. In multiparous cows, VDS had an effect on FSCR and time to pregnancy. Multiparous cows having a VDS-2 or a VDS-3 had decreased odds of pregnancy at first AI compared with cows having a VDS-0. Multiparous cows with VDS-1 or VDS-3 had a decreased hazard of conceiving within 200 DIM. The treatment effect of PGF2α was conditional on parity. In primiparous animals with PVD without a corpus luteum present at 32 DIM, treatment with PGF2α reduced FSCR. Irrespective of the presence of a corpus luteum, treatment with PGF2α decreased the hazard of conceiving within 200 DIM in primiparous cows. Although multiparous cows with PVD treated with PGF2α had increased odds of pregnancy at first AI, no treatment effect was observed on the hazard of conceiving within 200 DIM. Our results do not support the blanket use of PGF2α as a treatment option in postpartum dairy cows having PVD.

Association of postpartum hypocalcemia with early-lactation milk yield, reproductive performance, and culling in dairy cows

Periparturient hypocalcemia is frequently observed and considered as a gateway disease that is associated with various health issues. The objective of this study was to evaluate the association of hypocalcemia with early-lactation milk yield, reproductive performance, and culling across a large number of different managerial systems. A prospective cohort study was conducted based on a convenience sample of 125 dairy herds from 8 federal states of Germany between February 2015 and August 2016. A blood sample was drawn from 1,709 animals within 48 h after parturition and analyzed for serum calcium concentration. After discarding cows (n = 283) with missing data, a total of 1,426 cows were considered for final analyses. The median time from calving to sampling was 14.0 h (interquartile range = 5.0-24.9 h). For each herd, a record of the herd management software was requested 150 d after the last cow was sampled. Serum calcium concentration of each cow was associated with early-lactation milk yield (Dairy Herd Improvement Association equivalent test 1 to 3), reproductive performance [days in milk (DIM) at first artificial insemination (AI), pregnancy at first AI, time to pregnancy within 150 DIM], and culling (until 60 DIM) data. Generalized linear mixed models were used to analyze continuous or categorical data. Shared frailty models were used for time to event data. Five different thresholds were used to define hypocalcemia. Thresholds ranged from 1.8 to 2.2 mmol/L using 0.1-mmol/L increments. Clinical hypocalcemia was defined as serum calcium concentration <2.0 mmol/L in combination with clinical signs (e.g., recumbency). The effect of hypocalcemia on milk yield was conditional on parity. In primiparous cows a serum calcium concentration <2.0 mmol/L (6.4% of cows were below this threshold) had no effect on milk production, whereas there was a tendency for multiparous cows with a serum calcium concentration <2.1 mmol/L (63.2% of cows were below this threshold) to produce 0.80 kg/d more milk compared with multiparous cows at or above the threshold. Multiparous cows suffering from clinical hypocalcemia produced 2.19 kg/d less milk compared with normocalcemic cows in early lactation. Calcium status was not associated with days to first insemination. Cows with a serum calcium concentration <1.9 mmol/L (34.6% of cows below this threshold) had decreased odds (odds ratio = 0.56) of pregnancy at first AI. A serum calcium concentration <1.8 mmol/L (24.1% of cows below this threshold) had a significant effect on time to pregnancy. Compared with animals with a serum calcium concentration ≥1.8 mmol/L, the hazard of becoming pregnant within 150 DIM was reduced when cows had a serum calcium concentration <1.8 mmol/L (hazard ratio = 0.68). Cows with a serum calcium concentration <2.0 mmol/L (44.3% of cows were below this threshold) had a 1.69 times greater hazard of being culled within the first 60 DIM compared with normocalcemic animals. The present study shows that the association of hypocalcemia with milk yield was conditional on parity and serum calcium concentration measured once within 48 h after calving. Considering reproductive performance and culling in early lactation, a negative effect of postpartum hypocalcemia was demonstrated.

Short communication: Associations between blood glucose concentration, onset of hyperketonemia, and milk production in early lactation dairy cows

The objectives of this study were to describe the associations between hypoglycemia and the onset of hyperketonemia (HYK) within the first 6 wk of lactation, to evaluate the effects of body condition score at calving on glucose concentration, and to study the effects of hypoglycemia on milk production. A total of 621 dairy cows from 6 commercial dairy farms in Germany were enrolled between 1 and 4 d in milk (DIM). Cows were tested twice weekly using an electronic handheld meter for glucose and β-hydroxybutyrate (BHB), respectively, for a period of 42 d. Hypoglycemia was defined as glucose concentration ≤2.2 mmol/L. Hyperketonemia was defined as a BHB concentration ≥1.2 mmol/L. The onset of HYK was described as early onset (first HYK event within the first 2 wk postpartum) and late onset (first HYK event in wk 3 to 6 postpartum). The effect of ketosis status on blood glucose within 42 DIM was evaluated using a generalized linear mixed model. No effect was observed of HYK on glucose concentration in primiparous cows. Multiparous cows with early-onset HYK had a lower glucose concentration (-0.21 mmol/L) compared with nonketotic cows. Overall, primiparous cows had a lower prevalence and incidence of hypoglycemia than multiparous cows. Hypoglycemia in multiparous cows was associated with higher first test-day milk production and 100 DIM milk production. In conclusion, hypoglycemia mainly occurred in multiparous cows with early-onset HYK, whereas primiparous cows were at a lower risk for hypoglycemia.

Antibiotic treatment of metritis in dairy cows-A meta-analysis

The objective of this meta-analysis was to assess the efficacy of the treatment of bovine metritis with common antibiotic and nonantibiotic treatment options. Acute puerperal metritis, a systemic and potentially painful illness with rectal temperature >39.5°C and signs of toxemia due to an infection of the uterus, occurs within 21 d after parturition. Because of the infectious nature, antibiotics are considered beneficial for the treatment of acute puerperal metritis. Each use of an antimicrobial drug, however, is associated with selective pressure for eventual emergence of resistant bacteria. The 23 trials evaluated in the course of a previously conducted systematic review were the basis for meta-analytic investigations. Selected trials were screened regarding their eligibility for the following investigations: (1) comparison of different antibiotic treatments with respect to metritis prevalence at time of re-examination, (2) efficacy of ceftiofur treatment with respect to metritis prevalence at time of re-examination, (3) comparison of efficacy of antibiotic versus nonantibiotic drugs with respect to metritis prevalence at time of re-examination, and (4) equivalence assessment of treatment effects on reproductive performance measures. Where at least 3 trials had investigated the same outcome variable and met the inclusion criteria (inclusion of a control or reference group diagnosed with metritis; reporting means and standard deviation in case of continuous data), meta-analytic investigations were carried out. Due to a shortage of comparable studies, we could not conduct investigations (1) and (3). Ceftiofur treatment of 828 metritic cows was associated with a decrease in the prevalence of metritis following treatment in comparison to 804 untreated cows. In conclusion, meta-analytic investigations uncovered a need for more high-quality studies. Furthermore, a positive effect of the most commonly used antibiotic drug, ceftiofur, for the treatment of bovine metritis could be shown. A comparison with other antibiotic or nonantibiotic treatment options could not be made.

Evaluation of ear skin temperature as a cow-side test to predict postpartum calcium status in dairy cows

Subclinical hypocalcemia is considered a gateway disease that increases susceptibility to other metabolic and infectious diseases in transition dairy cows. In the absence of a cow-side test, however, it is difficult to identify hypocalcemic cows. The objective of this study was to evaluate ear skin temperature as a diagnostic predictor of serum calcium concentration. We conducted a cross-sectional study on 7 commercial dairy farms, involving 251 cows 0 to 48h after calving. Skin temperature of the ears (STEar) was scored manually by palpating both ears. An infrared thermometer was used to measure ear temperature, skin temperature on the coxal tuber (STCox), and ambient temperature. Rectal temperature was measured using a digital thermometer. A blood sample was drawn to determine serum calcium concentration. Hypocalcemia was defined as serum calcium below 2.0mmol/L, irrespective of clinical symptoms. Serum calcium concentration <2.0mmol/L in connection with clinical symptoms was defined as clinical milk fever; serum calcium concentration <2.0mmol/L without clinical symptoms was defined as subclinical hypocalcemia. Multivariate analysis using the GENLINMIXED procedure and receiver operating characteristic analysis were performed to evaluate whether serum calcium concentration could be predicted using ear temperature and other temperature estimates. The prevalence of hypocalcemia was 3.3, 27.3, 32.8, and 69.6% for cows in first, second, third, and fourth or greater lactation, respectively. None of the cows in first and second lactation had clinical milk fever. The prevalence of clinical milk fever was 6.0 and 20.3% for cows in their third and fourth or greater lactation, respectively. A decrease in ear temperature of 0.39°C [95% confidence interval (CI): 0.25-0.54] was associated with a decrease of 0.1mmol/L in serum calcium concentration. Ambient temperature, however, was a major confounder for ear temperature. With an increase in ambient temperature of 1°C, STEar rose by 0.78°C (95% CI: 0.67-0.90). Hypothermia was more pronounced in clinical milk fever (median 21.8°C; interquartile range 14.7-27.0°C) compared with subclinical hypocalcemia (median 27.6°C, interquartile range 22.1-30.8°C). All temperature estimates had only accurate test characteristics based on their area under the curve for prediction of subclinical hypocalcemia (area under the curve for STEar, STCox, and rectal temperature were 0.641, 0.668, and 0.606, respectively) when cows with clinical milk fever were excluded. Although ear temperature has been associated with serum calcium concentration, ear temperature cannot be recommended for diagnosis of subclinical hypocalcemia.

Glucose concentration in capillary blood of dairy cows obtained by a minimally invasive lancet technique and determined with three different hand-held devices

BACKGROUND

Dairy cows have a massive demand for glucose at the onset of lactation. A poor adaption to this period leads to an excessive negative energy balance with an increased risk for ketosis and impaired animal health and production. Besides the measurement of ketones, analysing the glucose concentration in blood is reported as helpful instrument for diagnosis and differentiation of ketosis. Monitoring metabolic parameters requires multiple blood sampling. In other species, new blood sampling techniques have been introduced in which small amounts of blood are rapidly analysed using electronic hand-held devices. The objective of this study was to evaluate the suitability of capillary blood for blood glucose measurement in dairy cows using the hand-held devices FreeStyle Precision (FSP, Abbott), GlucoMen LX Plus (GLX, A. Menarini) and the WellionVet GLUCO CALEA, (WGC, MED TRUST). In total, 240 capillary blood samples were obtained from dry and fresh lactating Holstein-Friesian cows. Blood was collected from the skin of the exterior vulva by using a lancet. For method comparison, additional blood samples were taken from a coccygeal vessel and analyzed in a laboratory. Glucose concentrations measured by a standard laboratory method were defined as the criterion standard.

RESULTS

The Pearson correlation coefficients between the glucose concentrations analyzed in capillary blood with the devices and the reference were 73% for the FSP, 81% for the GLX and 41% for the WGC. Bland-Altman plots showed biases of -18.8 mg/dL for the FSP, -11.2 mg/dL for the GLX and +20.82 mg/dL for the WGC. The optimized threshold determined by a Receiver Operating Characteristics analysis to detect hyperglycemia using the FSP was 43 mg/dL with a sensitivity (Se) and specificity (Sp) of 76 and 80%. Using the GLX and WGC optimized thresholds were 49 mg/dL (Se = 92%, Sp = 85%) and 95 mg/dL (Se = 39%, Sp = 92%).

CONCLUSIONS

The results of this study demonstrate good performance characteristics for the GLX and moderate for the FSP to detect hyperglycemia in dairy cows using capillary blood. With the study settings, the WGC was not suitable for determination of glucose concentrations.

Glucose concentration in capillary blood of dairy cows obtained by a minimally invasive lancet technique and determined with three different hand-held devices

Background

Dairy cows have a massive demand for glucose at the onset of lactation. A poor adaption to this period leads to an excessive negative energy balance with an increased risk for ketosis and impaired animal health and production.

Besides the measurement of ketones, analysing the glucose concentration in blood is reported as helpful instrument for diagnosis and differentiation of ketosis. Monitoring metabolic parameters requires multiple blood sampling. In other species, new blood sampling techniques have been introduced in which small amounts of blood are rapidly analysed using electronic hand-held devices.

The objective of this study was to evaluate the suitability of capillary blood for blood glucose measurement in dairy cows using the hand-held devices FreeStyle Precision (FSP, Abbott), GlucoMen LX Plus (GLX, A. Menarini) and the WellionVet GLUCO CALEA, (WGC, MED TRUST). In total, 240 capillary blood samples were obtained from dry and fresh lactating Holstein-Friesian cows. Blood was collected from the skin of the exterior vulva by using a lancet. For method comparison, additional blood samples were taken from a coccygeal vessel and analyzed in a laboratory. Glucose concentrations measured by a standard laboratory method were defined as the criterion standard.

Results

The Pearson correlation coefficients between the glucose concentrations analyzed in capillary blood with the devices and the reference were 73 % for the FSP, 81 % for the GLX and 41 % for the WGC. Bland-Altman plots showed biases of −18.8 mg/dL for the FSP, -11.2 mg/dL for the GLX and +20.82 mg/dL for the WGC. The optimized threshold determined by a Receiver Operating Characteristics analysis to detect hyperglycemia using the FSP was 43 mg/dL with a sensitivity (Se) and specificity (Sp) of 76 and 80 %. Using the GLX and WGC optimized thresholds were 49 mg/dL (Se = 92 %, Sp = 85 %) and 95 mg/dL (Se = 39 %, Sp = 92 %).

Conclusions

The results of this study demonstrate good performance characteristics for the GLX and moderate for the FSP to detect hyperglycemia in dairy cows using capillary blood. With the study settings, the WGC was not suitable for determination of glucose concentrations.

Effect of insemination after estrous detection on pregnancy per artificial insemination and pregnancy loss in a Presynch-Ovsynch protocol: A meta-analysis

Presynchronization of cows with 2 injections of prostaglandin administered 14d apart (Presynch-Ovsynch) is a widely adopted procedure to increase pregnancy per artificial insemination (P/AI) for the first service. In a Presynch-Ovsynch protocol, 2 different management strategies can be observed. Either all cows receive timed artificial insemination (onlyTAI) or cows detected in estrus after the second PGF2α injection are inseminated and the remaining cows without signs of estrus will be subject to timed AI (EDAI+TAI). A systematic review of the literature was performed with the objective to evaluate the effect of insemination after estrous detection during a Presynch-Ovsynch protocol for the first service on fertility in lactating dairy cows. Two statistical approaches were conducted using either a fixed or a random effects meta-analysis based on the heterogeneity among the experimental groups. Reproductive outcomes of interest were P/AI measured on d32 (d 28 to 42) and pregnancy loss between d32 and 60 (d 42 to 74) of gestation. In approach 1, 3 randomized controlled studies including 1,689 cows with the primary objective to evaluate the effect of insemination after estrous detection in a Presynch-Ovsynch protocol were used. The incorporation of insemination after estrous detection decreased the odds of pregnancy by 35% [odds ratio=0.65; 95% confidence interval (CI)=0.53-0.80] on d32 after AI using a fixed effects model. We detected no effect on pregnancy loss on d60 of gestation (odds ratio=0.88; 95% CI=0.55-1.43). There was no heterogeneity among the 3 studies regarding P/AI and pregnancy loss. In approach 2, cows from approach 1 and cohorts from another 17 experimental groups including 8,124 cows submitted to first AI using a Presynch-Ovsynch protocol were used. Information regarding pregnancy loss was available for 5,200 cows. In the random effects model, the overall proportion of P/AI was 30.9% (95% CI=26.71-35.28; n=2,400) and 41.7% (95% CI=39.76-42.01; n=7,413) on d32 after AI for EDAI+TAI and onlyTAI, respectively. The overall proportion of pregnancy loss was 11.7% (95% CI=6.11-18.8; n=1,811) and 9.6% (95% CI=6.37-13.33; n=3,389) on d60 after AI for EDAI+TAI and onlyTAI, respectively. We observed substantial heterogeneity among the experimental groups regarding P/AI and pregnancy loss. In summary, there was a benefit on P/AI for cows with 100% TAI after completing a Presynch-Ovsynch protocol.

Effect of a phase I Coxiella burnetii inactivated vaccine on body temperature and milk yield in dairy cows

Q fever is a zoonotic disease caused by Coxiella burnetii. The pathogen is prevalent in ruminants (goats, sheep, cows), which are the main sources of human infection. In the cattle industry around the world, animal (15 to 20%) and herd (38 to 72%) level prevalences of C. burnetii are high. Vaccination of ruminants against Q fever is considered important to prevent spreading of the disease and risk of infection in humans. However, published information on side effects of the Q fever vaccination under field conditions is limited for cows. The objective of this study was to investigate the effect of the phase I C. burnetii inactivated vaccine Coxevac on body temperature and milk yield in dairy cows. In 2 experiments, a total of 508 cows were randomly divided into 2 groups to determine the effect of first vaccination on body temperature and milk yield. The C. burnetii serostatus of all cows was tested before vaccination with an indirect ELISA. The first experiment took place in the teaching and research barn of the Clinic of Animal Reproduction at the Freie Universität Berlin. Temperature was measured vaginally in 10 cows in a crossover design. The second experiment was conducted on a commercial dairy farm. Milk yield of 498 cows was measured 1 wk before and 1 wk after vaccination. In a subset of 41 cows, temperature was measured rectally. In both experiments, body temperature increased significantly after vaccination (1.0 ± 0.9°C and 0.7 ± 0.8°C). A significant difference was also found in body temperature between vaccinated and control cows. Thirty percent of the vaccinated animals in experiment 1 showed reversible swelling at the injection site as a reaction to the vaccination. The results indicate that vaccination against Q fever causes a transient increase of body temperature that peaks in the first 12 to 24h and declines after that. In experiment 2, vaccinated cows (26.8 ± 0.39 kg/d) produced significantly less milk than did control cows (28.2 ± 0.44 kg/d) 7d after first vaccination. The cumulative milk loss after first vaccination was influenced by an interaction between C. burnetii serostatus and average milk yield 7d before first vaccination. This was considered as part of the physiological immune response. Three out of 10 vaccinated animals in experiment 1 showed painful swelling of the skin at the injection site, which had a maximum size of 14.0 × 14.0 × 1.1cm. In conclusion, a transient increase of body temperature and a decrease in milk yield is prevalent after Coxevac vaccination.

Suitability of capillary blood obtained by a minimally invasive lancet technique to detect subclinical ketosis in dairy cows by using 3 different electronic hand-held devices

The objective of this study was to evaluate the suitability of capillary blood obtained by a minimally invasive lancet technique to detect subclinical ketosis in 49 prepartum and 191 postpartum Holstein-Friesian cows using 3 different electronic hand-held devices [FreeStyle Precision (FSP, Abbott), GlucoMen LX Plus (GLX, A. Menarini), NovaVet (NOV, Nova Biomedical)]. The β-hydroxybutyrate (BHBA) concentration in serum harvested from coccygeal blood samples was analyzed in a laboratory and used as a reference value. Capillary samples were obtained from the skin of the exterior vulva by using 1 of 3 different lancets. In all samples, the concentration of BHBA was immediately analyzed with all 3 hand-held devices used in random order. All lancets used in the study were eligible for capillary blood collection but differed in the total number of incisions needed. Spearman correlation coefficients between the BHBA concentrations in capillary blood and the reference test were highly significant with 83% for the FSP, 73% for the NOV, and 63% for the GLX. Using capillary blood, the FSP overestimated the mean BHBA concentration compared with the reference test (+0.08 mmol/L), whereas the GLX and NOV underestimated the mean concentration (-0.07 and -0.01 mmol/L). When a BHBA concentration of 1.2 mmol/L in serum was used to define subclinical ketosis, the corresponding analyses of receiver operating characteristics resulted in optimized thresholds for capillary blood of 1.1 mmol/L for the NOV and GLX devices, and of 1.0 mmol/L for the FSP. Based on these thresholds, sensitivities (Se) and specificities (Sp) were 89 and 84% for the NOV, 80 and 89% for the GLX, and 100 and 76% for the FSP. Based on a serum BHBA concentration of 1.4 mmol/L, analyses of receiver operating characteristics resulted in optimized cut-offs of 1.4 mmol/L for the FSP (Se 100%, Sp 92%), 1.3 mmol/L for the NOV (Se 80%, Sp 95%), and 1.1 mmol/L (Se 90%, Sp 85%) for the GLX. Using these optimized thresholds for the specific hand-held meters, no significant differences between the devices in Se and Sp to detect subclinical ketosis in coccygeal blood were observed. Calculated test characteristics for analyzing capillary blood using the hand-held devices were numerically smaller compared with blood obtained from a coccygeal vessel, but overlapping confidence intervals indicate no statistical difference between the origin of the sample. Hence, this procedure seems to be suitable for ketosis monitoring in dairy cows, but further validation with more data from different farms is recommended.