Association between clinical hypocalcaemia and postpartum endometritis

Harnessing Vaginal Probiotics for Enhanced Management of Uterine Disease and Reproductive Performance in Dairy Cows: A Conceptual Review

Uterine disease in cattle impairs reproductive performance and profitability and increases antibiotic use and antimicrobial resistance. Thus, probiotics offer a promising alternative therapy. This review presents conceptual findings on the efficacy of probiotics in managing uterine diseases and fertility in cows. Probiotics containing Lactobacillus spp. and Bifidobacterium spp. individually or as composite formulations are known to improve fertility. Strategic intravaginal administration of these formulations would likely enhance uterine immunity, particularly during the postpartum period. While current findings on the benefits to uterine health are encouraging, there is still significant knowledge missing, including a lack of empirical information from large-scale field trials. This review underscores the need for evidence-based guidelines for probiotics, such as genomic selection of formulations, targeted delivery, or potential synergy with other interventions. Future research should address these gaps to maximize the potential of probiotics in managing uterine diseases and enhancing the reproductive health of dairy cattle.

Risk factors for ultrasound-diagnosed endometritis and its impact on fertility in Scottish dairy cattle herds

BACKGROUND

The aim of this study was to investigate the risk factors for and the impact of ultrasound-diagnosed endometritis (UDE) on lactating dairy cows' reproductive performance.

METHODS

Data were analysed from 1123 Holstein and Holstein-Friesian cows from two Scottish dairy farms. A reproductive ultrasound examination was conducted on two occasions, at 43 ± 3 and 50 ± 3 days in milk (DIM), to screen for hyperechoic fluid in the uterus. Statistical analyses were performed using multivariable logistic regression modelling and Cox proportional hazards models.

RESULTS

The overall incidence of UDE was 8.8% (99/1123). Risk factors for UDE included calving during autumn/winter seasons, increased parity and the presence of two or more diseases in the first 50 ± 3 days postpartum. The presence of UDE was associated with a reduced odds of pregnancy after all artificial inseminations up to 150 DIM.

LIMITATIONS

The retrospective design of this study led to some inherent limitations with the quality and quantity of data collected.

CONCLUSIONS

The findings of this study indicate which risk factors should be monitored in postpartum dairy cows to limit the impact of UDE on future reproductive performance.

Relationship between milk constituents from milk testing and health, feeding, and metabolic data of dairy cows

A new evaluation scheme to assess the nutritional status of dairy cows on the basis of milk constituents was derived from 7.37 million German records of milk testing. The aim of this work was to validate this new scheme. Two data sets with fertility and health information (data set A) and with measured energy and nutrient intake and metabolic characteristics (data set B) were analyzed. Data set A included 32 commercial dairy farms in northeast Germany, with 72,982 records of 43,863 German Holstein cows; data set B included 12 German experimental farms, with 49,275 records of 1,650 German Holstein, Simmental, and Brown Swiss cows. Milk traits were linked to health disorders and metabolic and feeding characteristics. Frequently used limits of milk constituents were compared with ranges of the new "Dummerstorf feeding evaluation." To distinguish an optimal from a deficient energy supply, a milk protein content ≥3.20% (previously used) and a milk fat:protein ratio (FPR) ≤1.4 (new scheme) were chosen and compared with feed energy intake in relation to demand. Energy status was more often correctly assigned by FPR than by milk protein content (80.7 and 68.7%, respectively). Over all data, the new optimum range of milk urea between 150 and 250 mg/L was better suited to dietary crude protein intake in relation to demand than the previously used range of 150 to 300 mg/L (42.4 and 38.0%, respectively). Ketosis or blood values associated with ketosis such as β-hydroxybutyrate >1.2 mmol/L or nonesterified fatty acids >1,000 µmol/L, as well as strong mobilization of body weight ≥1.5 kg/d, loss of back fat thickness ≥10 mm, and loss of body condition score ≥1 unit in first 60 days in milk were compared with different milk trait thresholds. For the updated scheme FPR >1.4 was used in combination with either milk protein content below the individual statistical lower limit of milk protein content, or milk fat content greater than the individual statistical upper limit of milk fat content; FPR >1.5 was taken as a frequently used threshold. For these ketosis indicators, the new scheme had higher sensitivities. Energy oversupply or the risk of overconditioning could not be identified by milk constituents alone. Urinary acid-base content was not related to milk content. Similarly, milk testing data did not allow a clear distinction to be made between the diagnoses of acidosis and, for example, ketosis. Essential requirements for good herd management are the continuous observation of milk testing data in combination with other established instruments of feeding and animal monitoring.

Metabolic markers for purulent vaginal discharge and subclinical endometritis in dairy cows

This study compares serum markers for systemic inflammation, and liver, mineral, and energy status in samples obtained -7, 1, 3, 5, 7, 14 ± 1, 21 ± 1, and 35 d relative to calving from healthy dairy cows and those diagnosed with purulent vaginal discharge (PVD) or subclinical endometritis (SCE). Metabolites and markers measured in serum were total calcium, total protein, albumin, globulin, cholesterol, urea, glucose, gamma-glutamyl transferase, aspartate aminotransferase, glutamate dehydrogenase, β-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), haptoglobin (Hp), and insulin-like growth factor-1 (IGF-1). Holstein cows with no recorded clinical disease were classified healthy (neither PVD nor SCE; n = 38), PVD (n = 10) or SCE (n = 10) at 35 d postpartum. The cut-point for PVD was mucopurulent vaginal discharge or worse, measured with Metricheck, and for SCE > 5% endometrial polymorphonuclear cells (PMN). Purulent vaginal discharge and SCE were mutually exclusive categories. The association of each serum marker with reproductive tract health classification was fitted in mixed linear regression models, accounting for repeated measures, sampling day, parity, BCS, and interactions of reproductive tract status and day. Serum Hp concentrations were greater at 3, 5, 7, and 14 ± 1 d postpartum for SCE and at 7 and 35 d postpartum for PVD than in healthy cows. Albumin concentrations were lesser for PVD than healthy at 14 ± 1 d postpartum and lesser for SCE than healthy at 35 d postpartum. The week before calving, SCE had lesser total calcium than healthy cows, and at 7 and 14 ± 1 d postpartum PVD had lesser total calcium than healthy cows. At 14 ± 1 d postpartum, serum NEFA, BHB, and globulin were greater, and IGF-1 lower for SCE than PVD or healthy cows. For all other metabolites, no differences were found. Before diagnosis, PVD or SCE had more indication of postpartum systemic inflammation (high Hp and low albumin) than healthy cows, and markers of energy status were more compromised in SCE than in PVD or healthy cows. This supports the hypothesis that SCE is associated with maladaptation to postpartum metabolic demands and with metabolic inflammation.

Cow-level risk factors for reproductive tract disease diagnosed by 2 methods in pasture-grazed dairy cattle in Ireland

The cow-side diagnosis of reproductive tract disease (RTD) involves identifying the presence of purulent vaginal discharge (PVD) and ultrasonographic endometritis (UE). The objectives of our study were to obtain prevalence estimates for RTD diagnosed by 2 methods (PVD and UE scoring) and to investigate the risk factors for increased probability of RTD if these methods are used in isolation or in combination. Our retrospective observational cohort study tested the hypothesis that RTD assessed by 2 methods would have similar risk factors, and that those would be mainly cow- and calving-related factors. We analyzed data from 5,049 pre-breeding examinations (PBE) from 2,460 spring-calved cows on 8 farms between 2014 and 2018. Cow-related details assessed were days in milk at PBE, breed, lactation number, dry period length, body condition score at calving and PBE, 305-d milk yield, predicted transmitting ability for production and fertility, the presence of a corpus luteum at PBE, and positive diagnosis the previous year. Calving details assessed were type of sire, calf sex, twinning, stillbirth, calving difficulty score, and retained fetal membranes. We conducted statistical analyses using 4 multivariable logistic regression models to identify the risk of RTD diagnosed by (1) PVD in isolation, (2) UE in isolation, (3) the presence of either PVD or UE; and (4) the presence of both PVD and UE. We accounted for herd, cow, and year as random effects in all 4 models. The overall prevalence of RTD in models 1, 2, 3, and 4 were 7.5, 6.7, 11.6, and 2.6%, respectively. Days in milk at PBE, the interaction between days in milk and retained fetal membranes, twinning, and the predicted transmitting ability for calving interval were consistently significant risk factors for positive scores in all 4 models. Considerable calving difficulty [adjusted odds ratio (AOR) = 13.64], Holstein Friesian dam breed (AOR = 2.58), first lactation (AOR = 2.39), and body condition score at PBE (AOR = 1.64) were risk factors for a positive PVD score but not for a positive UE score. Fifth lactation (AOR = 1.69), a beef-sired calf (AOR = 1.46), and the absence of a corpus luteum at PBE (AOR = 1.57) were risk factors for a positive UE score but not for a positive PVD score. These results support the hypothesis that most of the risk factors for PVD and UE are the same but some are distinctly different, implying that in some instances the 2 methods diagnose separate components of the RTD complex.

The Effect of Abnormal Reproductive Tract Discharge on the Calving to Conception Interval of Dairy Cows

Prolonged calving-to-conception interval (CCI) can increase economic loss in cattle. We investigated the effect of post-calving abnormal reproductive tract discharge (ARTD) on CCI in dairy cows and quantified the relationship of ARTD and associated risk factors with CCI. The source population was dairy cows that calved in the study period on three pasture-based, year-round calving farms in the Riverina, NSW, Australia. Farm records and records from veterinarians' visits were analyzed. ARTD was defined as the presence of reproductive tract discharge according to the following classification: per vaginum purulent discharge ≥21 days post-calving or mucopurulent discharge >26 days post-calving. The incidence of ARTD was calculated. A Kaplan-Meier survivor function was used to estimate median time to conception post-calving dependent on the presence or absence of ARTD. Mixed effects Cox-proportional hazard models were used to estimate the direct and indirect effects of ARTD, and other potential risk factors on CCI such as body condition score (BCS), ambient temperature, and milk yield. Model structures were guided by a directed acyclic graph of potential risk factors for ARTD. The incidence of ARTD in lactations was 16% (95% CI 13.8–18.5%) and did not differ significantly between the three farms (P > 0.05). The median CCI was 176 and 118 days for lactations with and without ARTD, respectively (P < 0.01). The rate of pregnancy following calving in cows with ARTD was significantly decreased relative to the rate of pregnancy in cows without (total effect hazard ratio = 0.62, se = 0.18, P = 0.01). High peak milk yield (>32 L) and parity >2 also significantly extended CCI. We did not observe an effect of BCS or ambient temperature on CCI. The incidence of ARTD in the current study was consistent with clinical endometritis (considered a major source of ARTD) reported in other studies. In contrast—and despite regular veterinary assessment and treatment of on the farms in this study—ARTD extended CCI. Evaluation of the economic impact of ARTD on dairy farms in this region is warranted, and methods to identify high risk cows and develop effective interventions are required.

Effect of blood ionised calcium concentration at calving on fertility outcomes in dairy cattle

Clinical and subclinical hypocalcaemia are common in dairy cows, yet evidence in the literature assessing their impact on fertility is inconsistent. The aim of this prospective cohort study was to examine associations between blood ionised calcium concentration at calving and fertility outcomes in dairy cattle. Blood samples were taken from 137 Holstein cows from four commercial dairy herds within 24 hours of calving and analysed for blood ionised calcium using an Epocal Point of Care Analyser (Epocal, Ottawa, Canada). Data collected from routine veterinary fertility examinations and herd records were used to investigate the association of ionised calcium with the outcomes: time to first service, time to conception and endometritis. There were significant negative associations between blood ionised calcium concentration and time to first service (HR 1.33, P=0.001) and blood ionised calcium concentration and time to conception (HR 1.16, P=0.04). There was no significant association between blood ionised calcium concentration and endometritis. The results of this study imply that management policies that minimise the reduction in blood ionised calcium concentration in the periparturient dairy cow are likely to improve reproductive outcomes and should be considered as part of the multifactorial approach to optimising dairy cow fertility.

The effect of metritis and subclinical hypocalcemia on uterine involution in dairy cows evaluated by sonomicrometry

The objective of this study was to examine the effects of metritis and subclinical hypocalcemia on reduction of uterine size in dairy cows using ultrasonography and sonomicrometry. Four piezoelectric crystals were implanted via laparotomy into the myometrium of the pregnant uterine horn of 12 pluriparous Holstein Friesian cows 3 weeks before the calculated calving date. Sonometric measurements were conducted daily from 2 days before parturition (= Day 0) until Day 14 after calving and then every other day until Day 28. Distances between adjacent crystals were expressed in relation to reference values obtained before calving. The diameter of the formerly pregnant uterine horn was measured using transrectal B-Mode sonography starting on Day 10. Cows were retrospectively divided into the following groups: cows without metritis (M-; n = 7), cows with metritis (M+; n = 5), cows with normocalcemia (SH-; Ca > 2.0 mmol/l on Days 1 to 3; n = 5) and cows with subclinical hypocalcemia (SH+; Ca < 2.0 mmol/l in at least one sample between Days 1 and 3; n = 7). Metritis did not affect (P > 0.05) sonometric measurements, but the diameter of the formerly pregnant horn was larger (P ≤ 0.05) between Days 15 and 21 in M+ cows than in M‒ cows. Reduction in uterine length in hypocalcemic cows was delayed (P ≤ 0.05) between Days 8 and 21 compared with normocalcemic cows, but the uterine horn diameter was not related to calcium status. In conclusion, both diseases affected reduction of uterine size until Day 28. Cows with metritis had a larger uterine diameter, possibly attributable to accumulation of lochia, and cows with subclinical hypocalcemia had delayed reduction of uterine length, presumably related to reduction of myometrial contractility.

Genes and environmental factors that influence disease resistance to microbes in the female reproductive tract of dairy cattle

Microbes commonly infect the female reproductive tract of cattle, causing infertility, abortion and post partum uterine diseases. When organisms reach the uterus, the resistance to disease depends on the balance between the classic triad of the virulence of the microbes, the host defence systems and the environment. The present review considers each aspect of this triad, using postpartum uterine disease as an exemplar for understanding disease resistance. The bacteria that cause postpartum uterine disease are adapted to the endometrium, and their microbial toxins cause tissue damage and inflammation. However, non-specific defence systems counter ascending infections of the female reproductive tract, and inflammatory responses in the endometrium are driven by innate immunity. Disease resistance to bacterial infection involves many genes involved in the maintenance or restoration of tissue homeostasis in the endometrium, including antimicrobial peptides, complement, cytokines, chemokines and Toll-like receptors. The most important environmental factors facilitating the development of postpartum uterine disease are related to trauma of the reproductive tract and to the metabolic stress of lactation in dairy cows. Long-term solutions for uterine disease will include genetic selection for disease resistance and optimising the care of the animal before, during and after parturition.

The effect of nutritional management of the dairy cow on reproductive efficiency

The cause of low fertility in dairy cows is multifactorial. Poor nutrition during the dry and early postpartum periods results in reduced glucose, insulin, insulin-like growth factor (IGF-I) and low LH pulse frequency with concomitant increases in beta-hydroxy butyrate, non-esterified fatty acids (NEFA) and triacylglycerol. Cows must mobilize large lipid, but also some protein reserves, with a consequent increased incidence of such metabolic disorders as hypocalcaemia, acidosis, ketosis, fatty liver and displaced abomasums. The occurrence of milk fever and ketosis affects uterine contractions, delays calving and increases the risk of retained foetal membranes (RFM) and endometritis. The nutritional risk factors that cause RFM are hypocalcaemia, high body condition score (BCS) at calving and deficiencies in Vitamin E and selenium. The risk factors for endometritis are hypocalcaemia, RFM, high triacylglycerol and NEFA. Thus, metabolic disorders predispose cows to gynaecological disorders, thereby reducing reproductive efficiency. Cows that are overconditioned at calving or those that lose excess body weight are more likely to have a prolonged interval to first oestrus, thereby prolonging days open. Nutritionally induced postpartum anoestrus is characterized by turnover of dominant follicles incapable of producing sufficient oestradiol to induce ovulation due to reduced LH pulse frequency. High nutrition can also increase metabolic clearance rate of steroid hormones such as progesterone or oestradiol. Lower concentrations of oestradiol on the day of oestrus are highly correlated with the occurrence of suboestrus, thereby making the detection of oestrus in high yielding cows even more difficult. Nutrition also affects conception rate (CR) to AI. Cows that develop hypocalcaemia, ketosis, acidosis or displaced abomasums have lower CRs and take longer to become pregnant. Excessive loss of BCS and excess protein content of the ration can reduce CR while supplemental fats that attenuate the production of F2alpha can improve CR. The increased metabolic clearance rate of progesterone (P4), which decreases blood concentrations during early embryo cleavage up to the blastocyst stage is associated with decreased CRs. In conclusion, poor nutritional management of the dairy cow, particularly before and after calving, is a key driver of infertility.