The efficacy of predicting dystocia in yearling beef heifers: I. Using ratios of pelvic area to birth weight or pelvic area to heifer weight

Identification of cow-level risk factors and associations of selected blood macro-minerals at parturition with dystocia and stillbirth in Holstein dairy cows

A deeper understanding of the risk factors for dystocia and stillbirth could help farmers make decisions about dairy cow management. The objectives of this study were to investigate cow-level risk factors associated with dystocia and stillbirth in a relatively large sample of dairy cows using multivariable linear regression models. The data consisted of 51,405 calving records of 14,546 Holstein cows from 3 dairy herds in Isfahan Province, Iran, collected between April 2011 and September 2017. To investigate the association between selected blood macro-minerals and the incidence of dystocia and stillbirth, blood samples were collected at the time of parturition from a random subset of these cows, which included 1311 animals. The incidence of dystocia and stillbirths averaged 14.7% and 4.3%, respectively. Results showed that calving year, calving season, dry period length, BCS, parity, calf sex, calf birth weight, twin status, and stillbirth were significantly associated with the incidence of dystocia. According to the Random Forest (RF) classifier, we found that dry period length, calf birth weight, and parity were the most important cow-level risk factors for the incidence of dystocia. Calving year, calving season, parity, twin status, dry period length, calf birth weight, calf sex, and dystocia were significantly associated with the incidence of stillbirths. The most important risk factors identified by the RF classifier for stillbirths were twin status, parity, dry period length, and calf birth weight. Also, interactions between the cow-level risk factors associated with dystocia and stillbirth were identified. The incidence of dystocia was associated with the interactions of twin status × calf birth weight and twin status × stillbirth. According to our analysis, the incidence of stillbirth is caused by interactions among several factors, such as twin status × length of dry period, twin status × calving season, and twin status × parity. The highest incidence of dystocia (21.3%) and stillbirths (5.4%) was observed in hypo-calcemic cows. In conclusion, twin status seems to be a determining factor for the incidence of stillbirths but not for dystocia. Finally, the results of this study may help the dairy industry make management decisions aimed at reducing dystocia and stillbirth rates.

Determining potential pregnancy status differences based on a new method of yearling heifer prebreeding examination

The study objective was to evaluate the Ready-Intermediate-Problem (RIP) replacement heifer evaluation matrix's ability to classify heifers into groups with differing reproductive outcomes. Beef heifers (n = 341) from six Kansas herds were classified according to RIP matrix guidelines and then exposed to AI breeding, bull breeding, or a combination of both as per the management plans for each participating herd. Following the breeding season the heifers were evaluated to determine pregnancy status, AI pregnancy status, days bred, and the number of 21 day cycles needed during the breeding season to become pregnant. After the breeding season, 298 (87%) of the heifers were pregnant, 204 (68%) of which became pregnant in the first 21 days of the breeding season. There was a significant interaction (P = 0.01) in RIP classification and pregnancy by 21 day cycle. Ready classified heifers had a significantly greater risk of becoming pregnant after a single AI exposure (P = 0.03) and in the first 21-day cycle (P = 0.02) compared to Problem classified heifers, and significantly less risk of being non-pregnant at the end of the breeding season (P < 0.01) compared to Problem classified heifers. The RIP matrix can be useful for classifying heifers prior to the onset of the breeding season. Further research is needed to evaluate the matrix in other settings and populations of U.S. beef heifers as well as at different intervals between evaluation and the start of breeding season.

Lactobacilli Dominance and Vaginal pH: Why Is the Human Vaginal Microbiome Unique?

The human vaginal microbiome is dominated by bacteria from the genus Lactobacillus, which create an acidic environment thought to protect women against sexually transmitted pathogens and opportunistic infections. Strikingly, lactobacilli dominance appears to be unique to humans; while the relative abundance of lactobacilli in the human vagina is typically >70%, in other mammals lactobacilli rarely comprise more than 1% of vaginal microbiota. Several hypotheses have been proposed to explain humans' unique vaginal microbiota, including humans' distinct reproductive physiology, high risk of STDs, and high risk of microbial complications linked to pregnancy and birth. Here, we test these hypotheses using comparative data on vaginal pH and the relative abundance of lactobacilli in 26 mammalian species and 50 studies (N = 21 mammals for pH and 14 mammals for lactobacilli relative abundance). We found that non-human mammals, like humans, exhibit the lowest vaginal pH during the period of highest estrogen. However, the vaginal pH of non-human mammals is never as low as is typical for humans (median vaginal pH in humans = 4.5; range of pH across all 21 non-human mammals = 5.4-7.8). Contrary to disease and obstetric risk hypotheses, we found no significant relationship between vaginal pH or lactobacilli relative abundance and multiple metrics of STD or birth injury risk (P-values ranged from 0.13 to 0.99). Given the lack of evidence for these hypotheses, we discuss two alternative explanations: the common function hypothesis and a novel hypothesis related to the diet of agricultural humans. Specifically, with regard to diet we propose that high levels of starch in human diets have led to increased levels of glycogen in the vaginal tract, which, in turn, promotes the proliferation of lactobacilli. If true, human diet may have paved the way for a novel, protective microbiome in human vaginal tracts. Overall, our results highlight the need for continuing research on non-human vaginal microbial communities and the importance of investigating both the physiological mechanisms and the broad evolutionary processes underlying human lactobacilli dominance.

Relationship between dam and calf characteristics with regard to dystocia in Belgian Blue double-muscled cows

Information concerning 493 single calvings of the double-muscled beef cow herd of the institute was collected to investigate the relationship between the characteristics of dams and calves with regard to dystocia. Factors affecting dystocia are similar in double-muscled cattle to those in non-double-muscled cattle but the occurrence of dystocia is greatly increased in double-muscled cows. Incidence of caesarean section was significantly correlated with parity (–0·243), age of dam (–0·232), post-partum dam weight (–0·185), and calf birth weight (0·164). Caesarean deliveries were required for 89·5% of the parturitions. Calvings without caesarean section were characterized by higher means for post-partum dam live weight (634·7 kg), age (1675·5 days), parity (3·1) and the ratio of post-partum dam weight to calf birth weight (14·4), compared with 580·2 kg, 1251·1 days, 2·1, and 11·8, respectively for births with caesarean setion, while calf birth weight was lower in non-caesarean calvings (45·8 v. 49·9 kg). Caesarean births involved more male calves than females (55 v. 45%). Even when calf birth weight was 30 kg or lower, and also in multiparous cows, 40 and 86% of the deliveries, respectively, still occurred with a caesarean section.

Incidence of caesarean section could not be accurately predicted from pre-partum characteristics such as pre-partum dam weight, age and parity.

Some maternal factors associated with dystocia in Belgian Blue cattle

Measurements of conformation and pelvic characteristics of pedigree Belgian Blue cows were compared in cattle from 11 herds. In seven herds comprising 56 cows caesarean sections were routinely used to deliver pedigree calves and in four herds comprising 52 cows they were given the opportunity to calve naturally per vaginum. Cows in the seven herds were approximately 10 months younger than those in the other herds. External pelvic measurements were linear distances between the tuber coxae, between the tuber coxarum and the tuber ischium, between the tuber ischii, the vertical distance between the underside of the tail and the tuber ischii, and heights of the tuber coxae and tuber ischii from the floor. Internal pelvic measurements were the vertical distance between the ventral body of the sacrum and the pubic symphysis and the horizontal distance between the wings of the ileum at the widest point of the pelvic inlet, both made with a Rice pelvimeter. Condition scores were assessed for all cows. There were correlations (P < 0·001) between internal pelvic height and width, external measurements, and age. For cattle that calved unassisted, pelvic height (P < 0·05) and area (P < 0·05) were significantly larger than those delivered by elective caesarean section. From internal pelvic measurements of 74 cows, those which always delivered live calves had a larger pelvic area (P < 0·01) than cows that delivered a dead foetus following any parturition.

Genome-wide association for heifer reproduction and calf performance traits in beef cattle

The aim of this study was to identify SNP markers that associate with variation in beef heifer reproduction and performance of their calves. A genome-wide association study was performed by means of the generalized quasi-likelihood score (GQLS) method using heifer genotypes from the BovineSNP50 BeadChip and estimated breeding values for pre-breeding body weight (PBW), pregnancy rate (PR), calving difficulty (CD), age at first calving (AFC), calf birth weight (BWT), calf weaning weight (WWT), and calf pre-weaning average daily gain (ADG). Data consisted of 785 replacement heifers from three Canadian research herds, namely Brandon Research Centre, Brandon, Manitoba, University of Alberta Roy Berg Kinsella Ranch, Kinsella, Alberta, and Lacombe Research Centre, Lacombe, Alberta. After applying a false discovery rate correction at a 5% significance level, a total of 4, 3, 3, 9, 6, 2, and 1 SNPs were significantly associated with PBW, PR, CD, AFC, BWT, WWT, and ADG, respectively. These SNPs were located on chromosomes 1, 5-7, 9, 13-16, 19-21, 24, 25, and 27-29. Chromosomes 1, 5, and 24 had SNPs with pleiotropic effects. New significant SNPs that impact functional traits were detected, many of which have not been previously reported. The results of this study support quantitative genetic studies related to the inheritance of these traits, and provides new knowledge regarding beef cattle quantitative trait loci effects. The identification of these SNPs provides a starting point to identify genes affecting heifer reproduction traits and performance of their calves (BWT, WWT, and ADG). They also contribute to a better understanding of the biology underlying these traits and will be potentially useful in marker- and genome-assisted selection and management.

A new application of pelvis area data as culling tool to aid in the management of dystocia in heifers

Although fetomaternal disproportion is the major cause of dystocia in heifers, pelvis area (PA) is not recommended as a culling tool due to its relatively low importance and genetic correlation with calf birth weight (BWT), the most important factor associated with dystocia. The objective of this observational study of 484 limited bred yearling beef heifers was to compare the effects of different methods of adjustment of PA data for culling to select against dystocia. Multivariable analyses were used to determine predictors of PA, calf BWT, and dystocia. Hypothetical culling rates of 10 and 20% were then applied after ranking heifers by each of the following: unadjusted PA, PA adjusted to 365 d of age by subtracting 0.27 cm(2) per day of age difference between each heifer's age and 365 d (APA), PA:prebreeding BW ratio (PA:BW), PA adjusted to the median BW of the group using the regression coefficient of PA on BW within age group (BWPA), and PA similarly adjusted to the median lean BW (LBWPA). Dam parity, sire, prebreeding age, prebreeding BW, and prebreeding BCS were associated with PA whereas dam parity, sire, own BWT, PA, AI bull, and calf gender were associated with calf BWT (P < 0.05). Dam parity, calf BWT, and either BWPA or LBWPA were the only independent predictors of dystocia (P < 0.05). Adjusting PA to BW or lean BW (LBW) improved the sensitivity and specificity to predict dystocia. After hypothetical culling by PA, retained heifers were heavier and had a higher calving rate and calves tended to be heavier at birth compared to culled heifers, but dystocia rates were not different. Culling by APA resulted in similar effects, except that dystocia rate tended to be lower in retained heifers. Culling by PA:BW resulted in lower dystocia rate in retained than in culled heifers, but retained heifers had lower prebreeding BW than culls. Culling by BWPA and LBWPA resulted in lower proportions with dystocia and a tendency towards higher calving rates in the retained heifers, without affecting the prebreeding BW or calf BWT. It is concluded that pelvimetry is a useful culling tool to aid in the management of dystocia in yearling heifers and that adjustment of PA to median BW or LBW within age group improves its accuracy and avoids the undesirable side effects.

An overview of calf diarrhea - infectious etiology, diagnosis, and intervention

Calf diarrhea is a commonly reported disease in young animals, and still a major cause of productivity and economic loss to cattle producers worldwide. In the report of the 2007 National Animal Health Monitoring System for U.S. dairy, half of the deaths among unweaned calves was attributed to diarrhea. Multiple pathogens are known or postulated to cause or contribute to calf diarrhea development. Other factors including both the environment and management practices influence disease severity or outcomes. The multifactorial nature of calf diarrhea makes this disease hard to control effectively in modern cow-calf operations. The purpose of this review is to provide a better understanding of a) the ecology and pathogenesis of well-known and potential bovine enteric pathogens implicated in calf diarrhea, b) describe diagnostic tests used to detect various enteric pathogens along with their pros and cons, and c) propose improved intervention strategies for treating calf diarrhea.

Residual feed intake adjusted for backfat thickness and feeding frequency is independent of fertility in beef heifers

Basarab, J. A., Colazo, M. G., Ambrose, D. J., Novak, S., McCartney, D. and Baron, V. S. 2011. Residual feed intake adjusted for backfat thickness and feeding frequency is independent of fertility in beef heifers. Can. J. Anim. Sci. 91: 573–584. This study examined the effects of residual feed intake (RFI), RFI adjusted for off-test backfat thickness (RFIfat) and RFI adjusted for off-test backfat thickness and feeding event frequency (RFIfat & activity) on heifer fertility and productivity. Beef heifers (n=190) were monitored for individual daily feed intake and feeding event activity over 108–112 d using the GrowSafe System® and assessed for age at puberty based on plasma progesterone concentration. Individual animal daily feed intake, feeding event activity and off-test backfat thickness were then used to calculate RFI, RFIfat and RFIfat & activity and group heifers as either negative ([−], RFI<0.0) or positive ([+], RFI≥0.0) for RFI. Heifers averaged 298 kg (SD=34) in body weight, were 276 days of age (SD=19) at the start of test, grew at 0.90 kg d−1 (SD=0.21), consumed 7.62 kg DM head−1 d−1 (SD=0.84) and had a feed conversion ratio of 8.93 (SD=2.43). Age (351 d, SD=43) and weight (367.3 kg, SD=45.0) at puberty were similar between [−] and [+] RFI heifers, but age at puberty was delayed in [−] RFIfat (P=0.04) and RFIfat & activity (P=0.08) heifers compared with [+] RFIfat and RFIfat & activity heifers. Efficient or [−] RFI heifer exhibited a lower pregnancy (76.84 vs. 86.32%, P=0.09) and calving rate (72.63 vs. 84.21%, P=0.05) compared with [+] RFI heifers. These differences were partially removed in [−] RFIfat and completely removed in [−] RFIfat & activity compared with their [+] RFI counterparts (pregnancy rate, 80.85 vs. 82.29%, P=0.80; calving rate, 75.53 vs. 81.25%, P=0.34). No differences were observed between efficient and inefficient heifers in calving difficulty, average calving date, age at first calving, calf birth weight, calf pre-weaning ADG, calf weaning weight and heifer productivity. However, [+] RFI heifers exhibited a 1.9-fold higher calf death loss compared with [−] RFI heifers (11.11% vs. 5.71%, P=0.24). This difference was more pronounced in [+] RFIfat and [+] RFIfat & activity heifers, which exhibited 2.2-fold (11.84% vs. 5.33%, P=0.15) and 3.0-fold (12.66% vs. 4.17%, P=0.06) higher calf death loss compared with [−] RFI heifers. There was no relationship of RFI adjusted for backfat thickness and feeding activity on fertility traits indicating that backfat thickness and feeding activity may be associated with feed intake and should be considered when selecting heifers for improved feed efficiency.

Plasma hormones and metabolites in Piedmontese cows during late pregnancy: relationships with calf birth weight

Relationships among plasma hormonal and metabolic variables in the last trimester of gestation in 59 Piedmontese dams (n = 15 heifers, n = 44 cows) and the calf birth weight (BWT) class of their offspring were investigated in seven herds. The BWT data were categorized as follows: > 50 kg (BWT-A), 46 to 50 kg (BWT-B), 41 to 45 kg (BWT-C), and < 41 kg (BWT-D). Blood samples were collected at 33, 36, and 39 wk of gestation. Packed cell volume (PCV) and plasma concentrations of insulin, estrone sulfate (E1SO4), NEFA, and creatinine were determined and correlated to BWT class. Creatinine: E1SO4 ratio also was calculated. Duration of gestation was greater for dams producing a BWT-A calf than for the other BWT classes, and calf BWT was heavier (P < 0.001) for calves in the BWT-A vs. BWT-D class. The heaviest calf in BWT-A was associated with the highest calving difficulty score. Insulin and PCV values were not affected by week of gestation, whereas plasma E1SO4, NEFA, and creatinine content increased (P < 0.001) and creatinine:E1SO4 decreased (P < 0.001) during late gestation. Calf BWT class did not affect PCV value. Plasma E1SO4 concentrations were lower (P < 0.01) in BWT-D dams than the other dams, showing the greatest difference at 39 wk of gestation. At 36 and 39 wk of gestation, dams bearing BWT-C and BWT-D calves had a higher (P < 0.01) plasma insulin concentration than those bearing BWT-A and BWT-B calves. Plasma NEFA concentrations at 39 wk of gestation were higher (P < 0.05) in dams of calf BWT-A than in the other dams. We conclude that plasma E1SO4 level is a variable that can be used to monitor problems related to a small size calf. Conversely, the forthcoming birth of a calf with a heavy BW seems to be preceded by a pronounced increase in plasma NEFA level in the dam just a few days before calving.

Calving and calving management of beef cows and heifers on cow-calf operations in the United States

A national sample of cow-calf producers was contacted to participate in a study to describe selected calving management practices on operations throughout the United States. Information was gathered on calving season, frequency of dystocia, frequency of observation, timing of assistance, and calving facilities. Regional and herd size differences existed in all parameters evaluated. Most calves (63.9%) were born in the months of February, March, and April. Overall, 16.7% of heifers and 2.7% of cows required some level of assistance in calving. Heifers and cows were checked an average of only 3.6 and 2.5 times per 24 h period during the calving season. Producers allowed heifers to labor for an average of 2.8h prior to lending assistance in calving while cows were allowed an average of 3.5h before providing assistance. In addition, only 39.6% of calvings took place in specialized calving areas presumably to allow increased observation frequency, timely intervention and protection from the elements. Collectively, these management practices illustrate that opportunities exist to improve calf survivability and increase reproductive efficiency in many cow herds.

Effects of severity of dystocia on cold tolerance and serum concentrations of glucose and cortisol in neonatal beef calves

Effects of dystocia on rectal temperature and serum cortisol and glucose concentrations, were studied in neonatal calves exposed to 0 degree C. Primiparous dams were observed continuously during parturition and if Stage II (labor) was not completed within 2 h after appearance of the allantochorion, delivery was completed with obstetrical assistance. Parturitions were scored (CDS) for difficulty and obstetric assistance required: CDS 1, no assistance (n = 8); CDS 2, minor manual assistance (n = 7); CDS 3, use of a mechanical calf puller (n = 5); CDS 4, cesarean section (n = 6). A blood sample, rectal temperature, and body weight were obtained within 30 min after birth. Calves were then fed 38 degrees C pooled colostrum, muzzled to prevent suckling, and placed back with their dam in a heated (22 degrees C) barn. At 4 h of age an indwelling jugular catheter was inserted. At 5 h of age calves were placed in a 0 degree C room for 140 min and blood samples and rectal temperatures were obtained every 10 or 20 min. A shivering score (1 = no shivering; 2 = moderate shivering; 3 = intense shivering) was assigned at each sampling time. Rectal temperatures were higher (P < 0.01) in CDS 1, 2 and 4 calves (39.0, 39.3, and 39.0 +/- .02 degrees C, respectively) than in calves with CDS 3 (38.3 +/- 0.02 degrees C) and were affected by duration of cold exposure (time; P < 0.01). Shivering was not affected by CDS but was affected by time (P < 0.01). Glucose concentrations were higher (P < 0.01) in CDS 3 calves (110.1 +/- 1.6 mg/dL) than in CDS 1, 2, or 4 calves (77.2, 86.4, and 89.0 +/- 1.3 mg/dL, respectively) and changed over time (P < 0.01). Cortisol concentrations were higher in CDS 1 calves (80.0 +/- 1.7 ng/mL) than in CDS 2, 3 or 4 calves (62.7, 58.2, and 57.7 +/- 2.0 ng/mL, respectively) and were affected by time (P < 0.01). We conclude that severe dystocia (CDS 3) resulted in lower calf rectal temperature, reduced serum cortisol, and increased serum glucose which could affect the ability of the calf to withstand cold stress. Minor dystocia did not cause and timely cesarean delivery prevented, the physiological aberrations encountered in severe dystocia.

Relationships of peri-partum, plasma concentrations of progesterone, oestrogens and 13,14-dihydro-15-ketoprostaglandin F2alpha in heifers and of anatomical measurements of dam and calf with difficulty of calving in early-bred Hereford x Friesian heifers

Plasma concentrations of progesterone, oestradiol-17beta, oestrone, oestrone sulphate and PGFM have been measured daily during the first peri-partum period of 45 Hereford x Friesian heifers bred at 11 months of age. Anatomical measurements of dam and calf were also recorded. Twelve of the calvings were scored easy, 33 difficult. Each of five models (fitted by linear logistic regression) relating difficulty of calving to the hormonal and anatomical measurements, predicts with at least 94% accuracy the calving score (easy or difficult) among the calvings. The models predict that increases of progesterone concentration on the day before calving, of oestrone sulphate concentration on the day after calving and of heifer heart girth decrease the odds of difficult calving, whereas increases of heifer body length and of calf head circumference increase the odds of difficult calving.

A retrospective analysis of factors contributing to calf mortality and dystocia in beef cattle

Records of 2191 calvings from the Clemson University Beef Physiology Unit between 1981 and 1993 were analyzed to determine factors affecting malpresentation, mortality and dystocia. Only 20 (0.91%) parturitions involved malpresentation: posterior presentation (n = 14), leg deviations (n = 3), head deviations (n = 2) and breech birth (n = 1). Dystocia affected calf mortality within 24 h of birth (P < 0.05), with mortality increasing as the severity of dystocia increased. There was an overall 4.5% death loss within 24 h of birth, with 4 and 7% mortality rates for calves from multiparous and primiparous dams, respectively (P < 0.05). Mortality was higher for bull vs heifer calves (P < 0.05). Ninety-four percent of calvings were unassisted, while 6% were assisted births. Dystocia was greater (P < 0.01) in primiparous (17%) than in multiparous dams (4%). In births involving dystocia, 28.1% required mild traction, 69.3% required heavy traction and 2.6% required Cesarean section. Birth weights associated with normal births and mild traction (36 and 36 kg) were lighter than those associated with heavy traction and Cesarean section (40 and 42 kg, respectively; P < 0.05). In conclusion, malpresentations were too few to be of significance, and dystocia influenced mortality within 24 h of birth. Calf birth weight and parity of dam explained most of the observed variations in dystocia.