Calving Ease Scores Research Articles

Birth Traits Associated with Pre-Adulthood Disease Manifestations in Calves.

The objective of this study was to explore the relationship between calf birth traits and their susceptibility to diseases before reaching adulthood. A total of 5253 birth traits of Chinese Holstein calves were examined, including gestation length (GL), calf weight at birth (CW), and calving ease score (CES), which ranges from 1 (easy) to 5 (very difficult). Furthermore, monthly medical records were scrutinized for pneumonia and diarrhea in these calves. The study assessed five aspects of disease manifestation in calves: age at first onset, frequency of illness, longest duration of treatment, and total duration of treatment. The link between age at onset and disease manifestation prior to adulthood was analyzed using general linear models and regression models. The GL of calves significantly correlated with the risk of pneumonia, with the risk decreasing as the GL increases. A higher CES was associated with a later onset of diarrhea in calves. Furthermore, the CES was significantly negatively correlated with the duration of diarrhea treatment in calves. These results suggest that implementing different preventive measures for calves with different birth traits and modifying treatment protocols for affected calves could enhance the productivity of dairy cows and reduce losses on farms.

The impact of beef sire breed on dystocia, stillbirth, gestation length, health, and lactation performance of cows that carry beef × dairy calves

In the United States, it is becoming common for dairy herds to mate a portion of cows to beef semen to create a value-added calf. The objectives of this study were to determine if dystocia risk, stillbirth (SB) risk, gestation length (GL), probability of early-lactation clinical disease events, early-lactation culling risk, or subsequent milk production differ between cows that carried calves sired by different beef breeds and those that carried Holstein-sired calves. Records from 10 herds contained 75,256 lactations from 39,249 cows that had calves with known Holstein or beef breed sires from the years 2010 to 2023. Calf sire breeds with ≥150 records included in analyses were Holstein, Angus, Simmental, Limousin, crossbred beef, and Charolais. Additional beef sire breeds that existed in lower frequency (n < 150 records) were condensed together and classified as "other." Because GL is a continuous variable, sire breed inclusion criteria were reduced to n ≥ 100 records; thus, Wagyu sires were included as their own breed group. Some records did not contain all variables of interest, thus models included fewer lactations depending on variable. Binomial generalized mixed models evaluated dystocia risk (defined as calving ease score ≥4 or calving ease score ≥3), SB risk, clinical health event risk (defined as lameness, mastitis, metabolic, reproductive, other, or any health events occurring within 60 d in milk [DIM]), and early culling risk (defined as death or culling within 60 DIM). Gestation length and test-date milk, fat, and protein yields were evaluated with mixed models. Calves sired by crossbred beef bulls had a greater probability of being stillborn (5%; 95% confidence interval lower = 2.9% upper = 9.0%) than those sired by Holstein bulls (2%; 95% confidence interval lower = 1.5%, upper = 2.7%). All beef-sired calves increased GL from that of Holstein-sired calves (277 ± 0.15 d) with Limousin (282 ± 0.81 d) and Wagyu-sired calves (285 d ± 0.79) resulting in the longest GL. The risk of dystocia, clinical health events, and early-lactation culling did not differ by calf sire breed nor did subsequent milk and component yield. Generally, carrying a calf sired by the beef breeds included in this study did not negatively affect the dairy cow.

Impact of Dystocia on Milk Production, Somatic Cell Count, Reproduction and Culling in Holstein Dairy Cows.

This study investigated the effects of dystocia on milk production, somatic cell count, reproductivity, disease, and milk production. A total of 2159 cows across 21 dairy farms in Alberta, Canada were enrolled in this study. Multivariable models were created to explore associations between outcome variables and calving ease score. In total, 89.5% of calvings were unassisted, 6.1% were an easy pull, and 4.3% were a moderate-hard pull. Cows that had a moderate-hard pull produced 4.01 kg less milk, 0.12 kg less volume of milk fat, and 0.12 kg less milk protein per day than those that had an unassisted calving. No difference was found between calving ease groups with respect to SCC. Cows with a moderate or hard pull produced 510 kg less milk per lactation than unassisted cows. Cows with a moderate to high level of assistance at birth had a higher hazard of being culled over the duration of their lactation. Cows with an easy pull had increased odds of developing a retained placenta. It is evident that assistance at calving, particularly a moderate-hard pull, is associated with significant impacts on future milk production and risk of being culled; therefore, efforts should be made to minimize dystocia and prevent these impacts.

157 Comparison of Reproductive and Early Growth Performance of an F1 Usda Prime Yield Grade one Carcass Clone Sire and an Industry-Leading Purebred Sire in the Beef x Dairy Production System

Abstract The objectives of this research were to determine if an F1 USDA Prime, yield grade 1 sire produced from the WTAMU PrimeOne Project (Sire A) was a competitive sire for producing dairy composites when compared to a purebred Angus sire (Sire B), and to evaluate any subsequent reproductive impact of sire on dam. Dairy cows (n = 1,930) were artificially inseminated resulting in 763 pregnancies with 564 births and 536 live calves. Data was collected at a large commercial dairy and analyzed using SAS 9.4 with sire as fixed effect; lactation, breeding technician and services per conception were random effects. Individual animal was experimental unit (n = 536). Conception rates were 40% for Sire A and 31% for Sire B (P ≤ 0.01). Average gestation length (GL) was 284-d and 280-d for Sire A and B, respectively (P ≤ 0.01). Calves by Sire B reported lower average birth weight (BW) than those by Sire A (P ≤ 0.01) with no difference in calving ease score (CE) (P = 0.24). There was no difference in 60-d (P = 0.58) or 120-d calf weights (P = 0.47). However, calves by Sire B reported higher average daily gains at both 60- (0.61 and 0.58 kg; P ≤ 0.01) and 120-d (0.70 and 0.67 kg; P = 0.03). Sire had no effect on morbidity (P = 0.62) or mortality (P = 0.25). Post-partum interval (PPI) and time from first estrus to conception were not different between sires (P = 0.19; P = 0.14). BW and CE did not affect PPI or time from first estrus to conception. Data from this trial indicates the cloned progeny sire increased conception rates, but the purebred Angus sire was more favorable for GL, BW and progeny growth performance. Neither sire negatively impacted subsequent reproductive performance of the dam.

Genetic parameters and genetic trends for reproductive traits in Egyptian buffalo

Reproductive traits are important for farm profitability because failure to reproduce is the primary reason for culling animals. Study objectives were to estimate genetic parameters and evaluate the trends for reproductive traits. Age at first calving (AFC), gestation length (GL), postpartum interval to pregnancy (PPIP), calving interval (CI) and calving ease score (CE) were recorded. A total of 38,906 records were available from 2426 buffalo cows. There was evaluation of genetic parameters using three models. The first model was applied to the first three parities fitting animal as a random effect. There was also a repeatability model utilized where data from all parities were evaluated to estimate heritability and repeatability. There was also a bivariate model to estimate genetic correlations between reproductive traits. Heritability estimates ranged from 0.0001 to 0.12 for PPIP and CE, respectively. Repeatability estimates were low to moderate ranging from 0.13 to 0.38 for PPIP and GL, respectively. There were close genetic correlations of 0.99 and - 0.93 between PPIP-CI and GL-CE, respectively. Genetic correlations between the other reproductive traits were low to moderate. Genetic trends for all reproductive traits were negative with and of a small magnitude, and regression coefficients were significant only for AFC and PPIP. The results from the current study supported the urgent need, not only for genetic or genomic selection improvement programs, but also for improving the farm management practices for reproductive traits in Egyptian buffalo.

Influence of Calving Ease on In-Line Milk Lactose and Other Milk Components.

Simple SummaryCalving is a difficult moment in a cow’s life that causes stress, and the ease of calving determines the course of further lactation. The hypothesis of our study was to investigate how the difficulty of calving may influence changes in lactose concentration and other milk components and how well these two factors correlate between each other. We found a statistically significant (p < 0.001) negative correlation of calving ease score with milk lactose % (r = −0.376) and positive correlation coefficients with milk lactose yield (kg) (r = 0.277) as well as milk fat/lactose % ratio (r = 0.191). The analysis showed a regular increase (p < 0.001) with decreasing calving ease scores for milk electric conductivity and milk somatic cell count.The aim of our study was to determine how the ease of calving of cows may influence changes in lactose concentration and other milk components and whether these two factors correlate with each other. To achieve this, we compared data of calving ease scores and average percentage of in-line registered milk lactose and other milk components. A total of 4723 dairy cows from nine dairy farms were studied. The cows were from the second to the fourth lactation. All cows were classified according to the calving ease: group 1 (score 1)—no problems; group 2 (score 2)—slight problems; group 3 (score 3)—needed assistance; group 4 (score 4)—considerable force or extreme difficulty. Based on the data from the milking robots, during complete lactation we recorded milk indicators: milk yield MY (kg/day), milk fat (MF), milk protein (MP), lactose (ML), milk fat/lactose ratio (MF/ML), milk protein/lactose ratio (MP/ML), milk urea (MU), and milk electrical conductivity (EC) of all quarters of the udder. According to the results, we found that cows that had no calving difficulties, also had higher milk lactose concentration. ML > 4.7% was found in 58.8% of cows without calving problems. Cows with more severe calving problems had higher risk of mastitis (SCC and EC). Our data indicates that more productive cows have more calving problems compared to less productive ones.

Classification and regression tree analysis to predict calving ease in Sussex heifers using pelvic area dimensions and morphological traits.

Objectives:The objective of this study was to assess the relationship between pelvic measurements, namely pelvic height (PH), pelvic area (PA), and pelvic width, and linear body measurement traits, such as hindquarters width, rump length (RL), hip height (HH), body weight (BW), shoulder height, chest depth (CD), body length, and also calve birth weight (CBW) under different calving ease scores, namely no assistance, gently pull, and hard pull.Material and Methods:A total of 51 first calf Sussex heifers at 24 months old, weighing approximately 440 ± 40.26 kg, were used for this study. Two-year-old bulls (n = 2), weighing approximately 800 kg, were used for mating the 51 heifers with a bull to cow ratio of 1:30 and 1:21. The fertility of bulls was assessed by a private veterinarian before the mating season. Calving ease was scored as follows: 1 = no assistance during parturition (normal), 2 = heifer assistance as gently pull, 3 = heifer assistance as hard pull, 4 = heifer cannot calf, 5 = heifer calved a dead calf, and 6 = heifer calf with the abnormal position.Results:Descriptive statistics indicated that PH (p < 0.01) and RL (p < 0.05) were positively remarkable and different among calving ease scores. Correlation results of the no assistance Sussex heifers group revealed that CBW was positively correlated (p < 0.05) with PH. Classification and regression tree CART results demonstrated that PH, BW, CD, and HH play an important role in predicting calving ease in Sussex heifers.Conclusion:The findings suggest that there is an association among PAs and biometric traits. The present study might help farmers select animals with higher PH, BW, CD, and HH during breeding to lower dystocia incidents during parturition. However, further studies need to be carried out in CART modeling to reduce dystocia in a larger sample size of Sussex heifers or other cattle breeds.

Effect of sexed semen on different production and functional traits in German Holsteins

The aim of this study was to analyze possible effects of semen type (conventional vs. female sexed) and calf sex on fertility and production traits. For this purpose, field data of German Holstein heifers in Lower Saxony were evaluated.Sexed semen was mainly used for first insemination. 87.0% female calves were born from sexed semen, while 52.7% female calves were born from conventional semen. Heifers inseminated with sexed semen were on average 43 to 48 days younger at their first calving than heifers inseminated with conventional semen.Calf sex had an influence on the average calving ease and the dystocia rates. Male calves showed higher calving ease scores and caused a higher risk for dystocia than female calves. The semen type had no influence on these characteristics.Within the same calf sex, sexed semen had only minor effects on most traits, except for stillbirth rates: the stillbirth rate for male calves from female sexed semen was 30.6%, which was 2.86 times the stillbirth rate of male calves from conventional semen, possibly due to trisomies.Sexed semen played only a minor role for production traits in first lactations.The extrapolated 305-day milk yield was 200 kg lower for first calf heifers, which were inseminated with sexed semen compared to heifers inseminated with conventional semen. Fat and protein yield were 6 kg to 8 kg lower after use of sexed semen. Animals with female offspring from sexed semen showed higher survival rates than the other groups.

Genetic parameters of calving ease in dairy cattle using threshold and linear models

Genetic parameters of direct and maternal effects for calving ease (CE) in Portuguese dairy cattle were estimated applying a threshold model (TM) and three linear models (LM) using 320,953 CE records. In LM, CE scores were directly used as dependent variables (LM1) or were transformed into values on an underlying continuous liability scale (average and maximum values for LM2 and LM3, respectively). The estimate of heritability for direct effects was lower on linear models (0.04–0.05) than in TM (0.09). Furthermore, direct heritability was higher than maternal heritability, ranging between 0.04–0.09 and 0.01–0.02, respectively. The genetic correlation between direct and maternal effects was negative in all models, ranging between –0.75 and –0.82. We investigated the association between bulls estimated breeding values (EBV) attained by TM and three LM, for 2223 bulls. Results show that all correlations were higher than 0.95 and slightly greater correlations were observed for direct effects than for maternal effects. Particular emphasis was given to individual differences between EBV ranking lists. The average difference between rank positions of TM and the three LM ranged from 64 to 122. Therefore, the selection of breeding animals is influenced by the model’s choice. Even with clear theoretical advantages in analysing categorical data, perhaps due to its more recent implementation, TM has not yet achieved the popularity of LM. The results of this work show that TM ranking list is more in accordance with LM2 than with LM1 or LM3. Therefore, with linear models, CE should be considered as average liability value instead of usual numerical score or maximum liability.

Short communication: Predictors of time to dairy calf bucket training

The time required to adequately bucket-train a dairy calf to drink its milk allotment is unknown. Additionally, factors that could predict calves who are slow to learn have not been identified. A prospective observational study was conducted to describe timing of bucket training and possible calf birth and colostrum quality factors that might predict calves requiring extra time to train. On one dairy farm, 1,235 calves were enrolled at birth in a prospective cohort study. Calving ease score, calf presentation at birth, twinning, calf sex, and dam parity were recorded by farm personnel. An as-fed colostrum sample for each calf was collected and evaluated for total solids, total plate bacterial count, and coliform bacterial count. Calf serum total protein values were obtained by d 2 to 3 of life. Calves were observed before the morning milk feeding for attitude/posture, and after feeding for assistance needed to drink milk from their bucket. Attitude/posture was significantly associated with whether a calf required assistance or not. Almost 60% (n = 724) of calves consumed their morning milk allotment (2 L) after d 3 of life without assistance. Significant factors associated with the odds of requiring assistance with drinking after 3 d of age included calf sex, being born a twin, and the week the calf was enrolled. Knowing how long it takes to train a calf to drink from a bucket could be useful in allocating the time or labor required to successfully train calves.

Reproductive performance of sexed versus conventional semen in Holstein heifers in various semiarid regions of Iran

For comparing reproductive performance of sexed versus conventional semen a total of 3573 heifer insemination records collected from five herds in four provinces of Iran were investigated. The studied provinces were classified into three regions: hot semiarid (Tehran and Alborz provinces), temperate semiarid (Khorasan Razavi province) and cold semiarid (Zanjan province). Various parameters including the conception rate, number of services per conception, calf sex ratio, calf birth weight, gestation length, calving ease score, abortion and stillbirth as well as twining rate were investigated. The logistic regression method was deployed for the analysis of categorical variables while the GLM procedure was applied for the analysis of continuous variables. The average conception rate of sex sorted and conventional semen was 48.3 and 63.8%, respectively. The utilisation of sex sorted semen resulted in 91.1% female calves. The conception rate, number of services per conception, gestation length, calf birth weight and the calf sex ratio were among the reproductive variables that were significantly influenced by the semen sexing. A greater number of services per conception and calving ease score were observed in hot and temperate semiarid areas. These climatic regions also provided a lower incidence of female calf births compared to the cold semiarid regions. Our results highly reaffirm the previous findings on the reproductive performance of sex sorted semen. Yet, climatic and management practices of a herd within a special climate have to be considered when deciding for utilisation of sex sorted semen in a dairy farm.

Genetic parameters of calving ease using sire-maternal grandsire model in Korean Holsteins.

ObjectiveCalving ease (CE) is a complex reproductive trait of economic importance in dairy cattle. This study was aimed to investigate the genetic merits of CE for Holsteins in Korea.MethodsA total of 297,614 field records of CE, from 2000 to 2015, from first parity Holstein heifers were recorded initially. After necessary data pruning such as age at first calving (18 to 42 mo), gestation length, and presence of sire information, final datasets for CE consisted of 147,526 and 132,080 records for service sire calving ease (SCE) and daughter calving ease (DCE) evaluations, respectively. The CE categories were ordered and scores ranged from CE1 to CE5 (CE1, easy; CE2, slight assistance; CE3, moderate assistance; CE4, difficult calving; CE5, extreme difficulty calving). A linear transformation of CE score was obtained on each category using Snell procedure, and a scaling factor was applied to attain the spread between 0 (CE5) and 100% (CE1). A sire-maternal grandsire model analysis was performed using ASREML 3.0 software package.ResultsThe estimated direct heritability (h2) from SCE and DCE evaluations were 0.11±0.01 and 0.08±0.01, respectively. Maternal h2 estimates were 0.05±0.02 and 0.04±0.01 from SCE and DCE approaches, respectively. Estimates of genetic correlations between direct and maternal genetic components were −0.68±0.09 (SCE) and −0.71±0.09 (DCE). The average direct genetic effect increased over time, whereas average maternal effect was low and consistent. The estimated direct predicted transmitting ability (PTA) was desirable and increasing over time, but the maternal PTA was undesirable and decreasing.ConclusionThe evidence on sufficient genetic variances in this study could reflect a possible selection improvement over time regarding ease of calving. It is expected that the estimated genetic parameters could be a valuable resource to formulate sire selection and breeding plans which would be directed towards the reduction of calving difficulty in Korean Holsteins.

Comparison of models for estimating genetic parameters and predicting breeding values for birth weight and calving ease in Czech Charolais cattle

The most appropriate model for genetic parameters estimation for calving ease and birth weight in beef cattle was selected. A total of 27 402 field records were available from the Czech Charolais breed. For estimation of genetic parameters for calving ease and body weight, three bivariate models were tested: a linear-linear animal model (L-LM) with calving ease classified into four categories (1 &amp;ndash; easy; 2&amp;ndash;4 &amp;ndash; most difficult), a linear-linear animal model (SC-LM) in which calving ease scores were transformed into Snell scores (Snell 1964) and expressed as percentage of assisted calving (ranging 0&amp;ndash;100%), and a bivariate threshold-linear animal model (T-LM) with calving ease classified into four categories (1 &amp;ndash; easy, 2&amp;ndash;4 &amp;ndash; most difficult). All tested models included fixed effects for contemporary group (herd &amp;times; year &amp;times; season), age of dam, sex and breed of a calf. Random effects included direct and maternal genetic effects, maternal permanent environmental effect, and residual error. Direct heritability estimates for calving ease and birth weight were, with the use of L-LM, SC-LM, and T-LM, from 0.096 &amp;plusmn; 0.013 to 0.226 &amp;plusmn; 0.024 and from 0.210 &amp;plusmn; 0.024 to 0.225 &amp;plusmn; 0.026, respectively. Maternal heritability estimates for calving ease and birth weight were, with the use of L-LM, SC-LM, and T-LM, from 0.060 &amp;plusmn; 0.031 to 0.104 &amp;plusmn; 0.125 and from 0.074 &amp;plusmn; 0.041 to 0.075 &amp;plusmn; 0.040, respectively. Genetic correlations of direct calving ease with direct birth weight ranged from 0.46 &amp;plusmn; 0.06 to 0.50 &amp;plusmn; 0.06 for all tested models; whereas maternal genetic correlations between these two traits ranged from 0.24 &amp;plusmn; 0.17 to 0.25 &amp;plusmn; 0.53. Correlations between direct and maternal genetic effects within-trait were negative and substantial for all tested models (ranging from &amp;ndash;0.574 &amp;plusmn; 0.125 to &amp;ndash;0.680 &amp;plusmn; 0.141 for calving ease and from &amp;ndash;0.553 &amp;plusmn; 0.122 to &amp;ndash;0.558 &amp;plusmn; 0.118 for birth weight, respectively), illustrating the importance of including this parameter in calving ease evaluations. Results indicate that any of the tested models could be used to reliably estimate genetic parameters for calving ease for beef cattle in the Czech Republic. However, because of advantages in computation time and practical considerations, genetic analysis using SC-LM (transformed data) is recommended.

Genetic parameters for direct and maternal calving ease in Walloon dairy cattle based on linear and threshold models.

Calving ease scores from Holstein dairy cattle in the Walloon Region of Belgium were analysed using univariate linear and threshold animal models. Variance components and derived genetic parameters were estimated from a data set including 33,155 calving records. Included in the models were season, herd and sex of calf × age of dam classes × group of calvings interaction as fixed effects, herd × year of calving, maternal permanent environment and animal direct and maternal additive genetic as random effects. Models were fitted with the genetic correlation between direct and maternal additive genetic effects either estimated or constrained to zero. Direct heritability for calving ease was approximately 8% with linear models and approximately 12% with threshold models. Maternal heritabilities were approximately 2 and 4%, respectively. Genetic correlation between direct and maternal additive effects was found to be not significantly different from zero. Models were compared in terms of goodness of fit and predictive ability. Criteria of comparison such as mean squared error, correlation between observed and predicted calving ease scores as well as between estimated breeding values were estimated from 85,118 calving records. The results provided few differences between linear and threshold models even though correlations between estimated breeding values from subsets of data for sires with progeny from linear model were 17 and 23% greater for direct and maternal genetic effects, respectively, than from threshold model. For the purpose of genetic evaluation for calving ease in Walloon Holstein dairy cattle, the linear animal model without covariance between direct and maternal additive effects was found to be the best choice.

Effects of reduced-fat modified wet distillers grains with solubles on the performance of limit-fed beef cows

<h2>ABSTRACT</h2> The objective of this study was to evaluate 3 inclusion rates for modified wet distillers grains with solubles containing 5.6 to 8.0% fat (WDGS) when limit-fed to beef cows during late gestation and early lactation. Angus × Simmental crossbred cows (n = 128) in the third trimester were blocked by parity (first parity and 2 or more parities) and stratified within parity by BW, subject to variation in BCS, to 16 pens. Four diets were fed until completion of a timed AI. Control cows were fed corn silage-, shelled corn-, and soybean meal-based diets to provide 12% CP [treatment (T) 1]. In the treatment diets, WDGS replaced shelled corn, soybean meal, and a portion of the corn silage to provide 12% (T2), 16% (T3), or 20% CP (T4). Analyzed CP values were 12.0, 12.5, 15.7, and 19.0%, for T1, T2, T3, and T4, respectively. Mean DMI per day was 7.80 ± 1.01, 7.96 ± 1.01, 8.55 ± 1.28, and 8.63 ± 1.11 kg for T1, T2, T3, and T4, respectively. No differences (P > 0.05) between treatments were observed for calving ease score, calf birth weight, calf BW, and cow BCS at the end of the feeding period. There was a linear (P = 0.03) increase in cow BW change in cattle fed increasing levels of WDGS and a quadratic response (P = 0.03) in milk production, with production increasing in T3 compared with T4 and T2 cattle. Cows fed increased levels of WDGS performed equally or superior to cows fed shelled corn- and soybean meal-based diets.

The effect of respiratory disease and a preventative antibiotic treatment on growth, survival, age at first calving, and milk production of dairy heifers

Bovine respiratory disease complex (BRD) is a common disease in weaned dairy calves that incurs economic and welfare costs. This study was an extension of a randomized clinical trial in which a single injection of tulathromycin (TUL) or oxytetracycline (TET) was administered at first movement to group housing for the prevention of BRD in the 60d following antimicrobial treatment (BRD60). Calves treated with TUL were 0.5 times [95% confidence interval (CI): 0.4 to 0.7] as likely to be treated for BRD60 as calves treated with TET. The objectives of the current study were to evaluate the long-term effects of BRD and antibiotic treatment on growth of heifers until breeding age, age at first calving, incidence of dystocia, milk production, and mortality before first calving and mortality before 120d in milk. At entry to the breeding barn (382d of age), calves that experienced BRD60 weighed 16.0±2.3kg less than calves that did not. Survival to first calving was recorded for 98% (1,343/1,392) of the heifers on this trial. For TET and TUL heifers with BRD60, 63% (94/150) and 73% (64/88) survived to first lactation, respectively. For TET and TUL calves without BRD60, 84% (436/517) and 84% (494/588) survived to first lactation, respectively. The median age at first calving for heifers with and without BRD60 was 714 (95% CI: 705–723) and 702 (95% CI: 699–705) days, respectively. Heifers with BRD60 were 1.5 (95% CI: 1.1–2.2) times more likely to have a calving ease score ≥2 at their first calving compared with heifers without BRD60. The administration of TUL at movement to group housing may have a role in the prevention of BRD and in mitigating some of the long-term effects of this disease.

Genetic evaluation for calving ease trait using linear and threshold models in first parity dairy cows

Calving ease (CE) is a categorical trait which can be analyzed by both linear and threshold models. Though it has been assumed that threshold models qualify to be the best procedure for analyzing categorical traits, its efficiency with field data has not been clearly confirmed. This study was aimed at comparing linear and threshold models for estimation of CE genetic parameters. Data consisted of 10,575 first parturition CE records collected from 1985 to 2006 in Isfahan, Iran. CE scores were classified into 5 categories depending upon parturition situation. A sire-maternal grand sire model, consisting of birth herd-year-season and sex-age as fixed effects and parturition herd-season, sire and maternal grand sire additive genetic values as random effects, was applied in MATVEC software. Mean, standard deviation, coefficient of variation, skewness, and kurtosis for first parity CE records were 0.233, 0.644, 276.640, 2.950, and 8.097, respectively. CE scores varied from 0 (86%) to 4 (0.1%). CE means for males (0.285) and female calves (0.190) were significantly different. Parturitions during winter and summer were associated with the highest and lowest calving difficulties, respectively. Estimations for direct and maternal heritability were 0.1082, 0.0486 using linear model and 0.0689, 0.0100 using threshold model, respectively. Even though departure from normal distribution was expected to favour the threshold model, implementation of this model in field data analysis did not eventuate to better genetic estimations. Key words: Calving ease, Holstein, Sire-MGS, threshold, genetic parameters.

Phenotypic effects of calving ease on the subsequent fertility and milk production of dam and calf in UK Holstein-Friesian heifers

The effect of calving ease on the fertility and production performance of both dam and calf was studied in approximately 50,000 and 10,000 UK Holstein-Friesian heifers and heifer calves, respectively. The first objective of this study was to estimate the effect of a difficult calving on the subsequent first-lactation milk production by estimating lactation curves using cubic splines. This methodology allows the estimation of daily milk, protein, and fat yields following calvings of differing degrees of difficulty. Losses in milk yield after a difficult calving have been quantified previously; however, estimates are generally restricted to the accumulated yields at specific days in lactation. By fitting cubic splines, gaps (in which the shape of the lactation curve can be merely guessed) between estimations were avoided. The second objective of this study was to estimate the effect of a difficult birth on the subsequent performance of the calf as an adult animal. Even though the calving process is known to involve cooperation between dam and calf, the effect of a difficult calving has, until now, only been estimated for the subsequent performance of the dam. Addressing the effects of a difficult birth on the adult calf strengthens the importance of calving ease as a selection trait because it suggests that the benefit of genetic improvement may currently be underestimated. The effect of calving ease on the subsequent reproductive performance of dam and calf was analyzed using linear regression and with calving ease score fitted as a fixed effect. Dams with veterinary-assisted calvings required 0.7 more services to conception and 8 more days to first service and experienced a 28-d longer calving interval in first lactation compared with dams that were not assisted at calving. Effects of calving ease on the reproductive performance of the adult calf in first lactation were not detected. Losses in milk yield of the dam were significant between d 9 to 90 in milk subsequent to a veterinary-assisted calving, creating a loss of approximately 2kg of milk per day, compared with a nonassisted calving. Calves being born with difficulties showed a significant reduction in milk yield in first lactation, demonstrating the lifelong effect of a difficult birth. Compared with nonassisted calves, veterinary-assisted calves showed a loss of 710kg in accumulated 305-d milk yield, which was significant from 129 to 261 d in milk. This suggests that from birth to production, physiological effects of a bad calving are not negated. Results furthermore suggest a beneficial effect of farmer assistance at calving on the milk yield of both dam and calf, when moderate difficulties occurred.

Case report

This case report illustrates how a farm-specific training program aimed at teaching employees to properly manage the cow at parturition can improve animal health on the dairy. Numerous primiparous cows on a 700-cow Holstein dairy farm were reported by the herd veterinarian to have severe intra-pelvic inflammation and uterine infection after calving, requiring extended systemic antibiotic therapy. The farm's previous maternity protocol called for moving cows directly to the maternity pen from the close-up dry cow group when parturition was imminent. Cows were generally moved to the calving pen during the first stage labor. Farm employees were subsequently provided a review of obstetrics principles, and the maternity protocol was revised to move cows to the maternity pen upon reaching second stage labor. Following implementation of the new protocol, average calving ease scores and outcome variables of proportion of cows with veterinary diagnosed metritis, veterinary prescribed penicillin for puerperal metritis, and stillborn calves in 2009 were compared to the herd's previous records from 2008. Average calving ease scores were lower for multiparous cows having heifer calves, and fewer heifer calves required delivery assistance. There were no differences in the other outcome variables, suggesting that multiparous cows could be moved to the maternity pen in either stage 1 or stage 2 labor. In primiparous cows in 2009 compared to 2008. There was a significant decrease in the proportion of primiparous cows delivering bull calves that received veterinary prescribed penicillin treatment for puerperal metritis. In addition, there was a significant decrease in both average calving ease scores and percent of either heifer or bull calves delivered requiring assistance in 2009, suggesting an advantage to waiting until stage 2 labor to move primiparous cows to the maternity pen. Overall, moving cows directly to the maternity pen in stage 2 labor from the close-up pen was an acceptable cow movement strategy on this dairy. Results from this study show that the veterinarian is ideally suited to provide farm-specific employee training, and well trained employees managing dairy cows at calving time will improve postpartum dairy cow health and welfare.

Estimation of genetic parameters for measures of calf survival in a population of Holstein heifer calves from a heifer-raising facility in New York State

The objectives of this study were to estimate the genetic parameters of survival to weaning and survival to exit for a population of Holstein calves from New York State, as well as to associate the estimated breeding values determined in the current study with traits from ongoing genetic evaluations used in Canada and the United States. Data were recorded for 7,372 heifer calves at a commercial rearing facility in New York State from arrival at 1 to 7 d of age for the duration of stay at the facility (on average, heifers departed the facility 1 mo before calving). Performance and disease up to weaning and mortality before and after weaning were recorded. Analyzed data were limited to daughters of sires with at least 10 calves originating from farms that had sent a minimum of 5 calves to be raised at the facility. As such, calves from 264 sires and 36 herds were studied using 2 statistical methods. The first method, calf survival, used a Weibull proportional hazards model, with survival defined as age at culling, death, or censoring. The second method, a 2-trait sire model, included survival from arrival to weaning (SUV1) and survival from weaning to exit (SUV2). Both models included fixed effects of arrival weight, serum total protein, weaning weight, season and year of birth, and calving ease score. Herd and sire were included as random effects. Significant associations among all fixed effects and calf survival were observed. In general, very light or heavy weight at arrival, low total protein, low weaning weight, and difficult birth increased risk of mortality for calves. The heritability of survival from the first method was 0.063. The heritabilities from the linear model were 0.001 for SUV1 and 0.036 for SUV2. The genetic correlation between SUV1 and SUV2 was 0.58. Genetic variance was close to zero for survival of calves to weaning, but was greater for survival after weaning through the growing period. Breeding values were estimated for SUV1 and SUV2 and correlated with routinely evaluated traits from Canadian and US genetic evaluations. Significant associations between genetic evaluations for survival traits and routinely evaluated traits in Canada and the United States were found, in particular with conformation body traits, somatic cell score, fertility, and longevity.