Herdlife Lactation Yield,Herdlife, and Survival of Holstein and Ayrshire-Based Lines of Dairy Cattle

Length of herdlife, lifetime milk and component yields, daily milk and component yields, and survival rates were assessed from multiple lactation records of 927 cows in a Holstein line and an Ayrshire-based synthetic line. Holstein cows were progeny of random matings to either Holstein untested sires or progeny-tested Canadian and American Holstein sires. Ayrshire cows were randomly mated to Ayrshire untested sires or Canadian and American Ayrshire, Finnish Ayrshire, Norwegian Red, or Brown Swiss progeny-tested sires to produce the foundation females in the Ayrshire-based synthetic line.The Holstein cattle produced more milk and protein per day of milking herdlife or total herdlife than cows in the Ayrshire-based line and proportionately more survived to initiate second lactations. Daughters of the progeny-tested American and Canadian Holstein sires had significantly higher lifetime and daily milk, protein, and fat yields than daughters of young untested Holstein sires whereas lifetime yields of daughters of untested and progeny-tested Ayrshire sires were equivalent.     

Factors associated with frequency of abortions recorded through Dairy Herd Improvement test plans

Frequency of abortions recorded through Dairy Herd Improvement (DHI) testing was summarized for cows with lactations completed from 2001 through 2009. For 8.5 million DHI lactations of cows that had recorded breeding dates and were >151 d pregnant at lactation termination, the frequency of recorded abortions was 1.31%. Effects of year, herd-year, month, and pregnancy stage at lactation termination; parity; breed; milk yield; herd size; geographic region; and state within region associated with DHI-recorded abortion were examined. Abortions recorded through DHI (minimum gestation of 152 d required) were more frequent during early gestation; least squares means (LSM) were 4.38, 3.27, 1.19, and 0.59% for 152 to 175, 176 to 200, 201 to 225, and 226 to 250 d pregnant, respectively. Frequency of DHI-recorded abortions was 1.40% for parity 1 and 1.01% for parity ≥ 8. Abortion frequency was highest from May through August (1.42 to 1.53%) and lowest from October through February (1.09 to 1.21%). Frequency of DHI-recorded abortions was higher for Holsteins (1.32%) than for Jerseys (1.10%) and other breeds (1.27%). Little relationship was found between DHI-recorded abortions and herd size. Abortion frequencies for effects should be considered to be underestimated because many abortions, especially those caused by genetic recessives, go undetected. Therefore, various nonreturn rates (NRR; 60, 80, …, 200 d) were calculated to document pregnancy loss confirmed by the absence of homozygotes in the population. Breeding records for April 2011 US Department of Agriculture sire conception rate evaluations were analyzed with the model used for official evaluations with the addition of an interaction between carrier status of the service sire (embryo's sire) and cow sire (embryo's maternal grandsire). Over 13 million matings were examined using various NRR for Holstein lethal recessive traits (brachyspina and complex vertebral malformation) and undesirable recessive haplotypes (HH1, HH2, and HH3) as well as >61,000 matings for a Brown Swiss haplotype (BH1), and 670,000 matings for a Jersey haplotype (JH1). Over 80% of fertility loss occurred by 60 d after breeding for BH1, HH3, and JH1, by 80 d for HH2, by 100 d for BY, and by 180 d for HH1. For complex vertebral malformation, fertility loss increased from 40 to 74% across gestation. Association of undesirable recessives with DHI-recorded abortions ranged from 0.0% for Jerseys to 2.4% for Holsteins.     

Genomic evaluation,breed identification,and discovery of a haplotype affecting fertility for Ayrshire dairy cattle

Genomic evaluations of dairy cattle in the United States have been available for Brown Swiss, Holsteins, and Jerseys since 2009. As of January 2013, 1,023 Ayrshires had genotypes in the North American database. Evaluation accuracy was assessed using genomic evaluations based on 646 bulls with 2008 traditional evaluations to predict daughter performance of up to 180 bulls in 2012. Mean gain in reliability over parent average for all traits was 8.2 percentage points. The highest gains were for protein yield (16.9 percentage points), milk yield (16.6 percentage points), and stature (16.2 percentage points). Twelve single nucleotide polymorphisms were useful for Ayrshire breed determination. Fewer breed-determining SNP were available for Ayrshires than for Holsteins, Jerseys, and Brown Swiss because of the similarity of Ayrshires and Holsteins. A haplotype that affects fertility was identified on chromosome 17 and traces back in the genotyped population to the bull Selwood Betty’s Commander (born in 1953). The haplotype carrier frequency for genotyped Ayrshires was 26.1%. Sire conception rate was decreased by 4.3 ± 2.5 percentage points for carriers of the haplotype as determined by 618 matings of carrier sire by carrier maternal grandsire. Genomic evaluations for Ayrshires were officially implemented in the United States in April 2013.     

Realized genetic selection differentials in Canadian Ayrshire,Jersey, and Brown Swiss dairy cattle populations

Estimated breeding values of a selection index, production, durability, health, and fertility traits from Canadian Ayrshire, Jersey, and Brown Swiss bulls and cows were used to study genetic selection differentials (GSD). The bulls and cows were born from 1950 and 1960, respectively. The GSD for the 3 Canadian dairy populations were studied along the 4-path selection model: sire-to-bull (SB), dam-to-bull (DB), sire-to-cow (SC), and dam-to-cow (DC) pathways. We also determined the variations in realized GSD due to herd and herd × year of conception in addition to the effects of some environmental factors on realized GSD of the SC and DC paths. The mean realized GSD of the DB were higher than those of other paths and were increasing for lifetime performance index, 305-d milk yield, 305-d fat yield, and 305-d protein yield in all 3 dairy cattle populations. We observed no clear trends in realized GSD for type traits in all 3 dairy cattle breeds except for the apparent increasing trends in realized GSD of mammary system, dairy strength, and feet and legs in the DB and SC paths of the Ayrshire breed. No clear patterns were observed in the realized GSD of daughter fertility in the SB, DB, and SC paths of all dairy cattle breeds. Realized GSD for somatic cell score showed increasing and favorable trends in the 3 most influential selection paths (SB, DB, and SC). Year of conception influenced realized GSD of artificial insemination bulls in Ayrshire, Jersey, and Brown Swiss dairy populations. Selection emphases for the SC path generally increased with time. There was considerable variation among herds in selection pressures applied in the SC and DC pathways but no clear association with housing system or region. This study demonstrates that variations exist among herds of minor dairy cattle breeds in their selection for economically important traits. These variations offer opportunities for further improvements in these populations.     

Genetic analysis of fertility traits in Israeli Holsteins by linear and threshold models.

Conception rates of Israeli Holstein cows and heifers were analyzed separately by linear and threshold models. Fixed effects for both data files were insemination number, AI institute, geographical region, and calendar month. Analysis of cows also included the fixed effects of parity, calving status, and DIM at insemination. Random effects included in the models were herd-year-season, insemination technician, sire of cow, and service sire. Fixed effect solutions for heifers and cows were not similar. For cows, insemination month had the greatest effect on conception rate. Heritability of conception rate ranged from 2 to 3.5% for heifers and from 1 to 2% for cows. Correlations between corresponding threshold and linear model random effect solutions were all greater than or equal to .99. Correlations between heifer and cow analyses for sire and service sire solutions were less than .4. Analysis with an incorrect herd-year-season variance component affected only the technician solutions.     

Genetic parameters of semen quality traits and genetic correlations with service sire nonreturn rate in Nordic Holstein bulls

Despite the importance of the quality of semen used in artificial insemination to the reproductive success of dairy herds, few studies have estimated the extent of genetic variability in semen quality traits. Even fewer studies have quantified the correlation between semen quality traits and male fertility. In this study, records of 100,058 ejaculates collected from 2,885 Nordic Holstein bulls were used to estimate genetic parameters for semen quality traits, including pre- and postcryopreservation semen concentration, sperm motility and viability, ejaculate volume, and number of doses per ejaculate. Additionally, summary data on nonreturn rate (NRR) obtained from insemination of some of the bulls (n = 2,142) to cows in different parities (heifers and parities 1–3 or more) were used to estimate correlations between the semen quality traits and service sire NRR. In the study, low to moderate heritability (0.06–0.45) was estimated for semen quality traits, indicating the possibility of improving these traits through selective breeding. The study also showed moderate to high genetic and phenotypic correlations between service sire NRR and some of the semen quality traits, including sperm viability pre- and postcryopreservation, motility postcryopreservation, and sperm concentration precryopreservation, indicating the predictive values of these traits for service sire NRR. The positive moderate to high genetic correlations between semen quality and service sire NRR traits also indicated that selection for semen quality traits might be favorable for improving service sire NRR.     

Analysis of the relationship between workability traits and functional longevity in Canadian dairy breeds

The aim of this study was to assess the effect of workability traits like milking speed and temperament on functional longevity of Canadian dairy cattle using a Weibull proportional hazards model. First-lactation data consisted of the following: 1,728,289 and 2,426,123 Holstein cows for milking temperament and milking speed, respectively, from 18,401 herds and sired by 8,248 sires; 39,618 and 60,121 Jersey cows for milking temperament and milking speed, respectively, from 1,845 herds and sired by 2,413 sires; and 54,391 and 94,847 Ayrshire cows for milking temperament and milking speed, respectively, from 1,316 herds and sired by 2,779 sires. Functional longevity was defined as the number of days from the first calving to culling, death, or censoring adjusted for production. Milking temperament and milking speed were recorded on a 1- to 5-point scale from very nervous to very calm and from very slow to very fast, respectively. The statistical model included the effects of stage of lactation; season of production; the annual change in herd size; type of milk recording supervision; age at first calving; effects of milk, fat, and protein yields calculated as within herd-year-parity deviations; herd-year-season of calving; sire; and milking temperament or milking speed class. The relative culling rate was calculated for animals in each milking temperament or milking speed class after accounting for the above-mentioned effects. The study showed that there was a statistically significant association between workability traits and functional longevity. Very nervous cows were 26, 23, and 46% more likely to be culled than very calm cows in Holstein, Ayrshire, and Jersey breeds, respectively. Similarly, very slow milkers were 36, 33, and 28% more likely to be culled than average milkers in Holstein, Ayrshire, and Jersey breeds, respectively. Additionally, very fast milkers were 11, 13, and 15% more likely to be culled than average milkers in Holstein, Ayrshire, and Jersey breeds, respectively. Producers might want to avoid consequences associated with the fast milkers such as udder health problems.     

Estimates of genetic parameters for Canadian Holstein female reproduction traits

Age at first insemination, days from calving to first insemination, number of services, first-service nonreturn rate to 56 d, days from first service to conception, calving ease, stillbirth, gestation length, and calf size of Canadian Holstein cows were jointly analyzed in a linear multiple-trait model. Traits covered a wide spectrum of aspects related to reproductive performance of dairy cows. Other frequently used fertility characteristics, like days open or calving intervals, could easily be derived from the analyzed traits. Data included 94,250 records in parities 1 to 6 on 53,158 cows from Ontario and Quebec, born in the years 1997 to 2002. Reproductive characteristics of heifers and cows were treated as different but genetically correlated traits that gave 16 total traits in the analysis. Repeated records for later parities were modeled with permanent environmental effects. Direct and maternal genetic effects were included in linear models for traits related to calving performance. Bayesian methods with Gibbs sampling were used to estimate covariance components of the model and respective genetic parameters. Estimates of heritabilities for fertility traits were low, from 3% for nonreturn rate in heifers to 13% for age at first service. Interval traits had higher heritabilities than binary or categorical traits. Service sire, sire of calf, and artificial insemination technician were important (relative to additive genetic) sources of variation for nonreturn rate and traits related to calving performance. Fertility traits in heifers and older cows were not the same genetically (genetic correlations in general were smaller than 0.9). Genetic correlations (both direct and maternal) among traits indicated that different traits measured different aspects of reproductive performance of a dairy cow. These traits could be used jointly in a fertility index to allow for selection for better fertility of dairy cattle.     

Genetic analysis of calving difficulty and stillbirth in Norwegian Red cows

The objectives of this study were to infer genetic parameters for stillbirth (SB) and calving difficulty (CD) and to evaluate phenotypic and genetic change for these traits in the Norwegian Red breed. Stillbirth is recorded as a binary trait and calving difficulty has 3 categories: 1) easy calving, 2) slight problems, and 3) difficult calving. The overall mean frequency of SB in Norwegian Red was 3% at first calving and 1.5% for second and later calvings; mean frequency of the category “difficult calving” was 2 to 3% for heifers and 1% for cows at second and later calvings. Mean stillbirth rate has remained unchanged from 1978 to 2004. The proportion of the category “difficult calving” has not changed over the years, but the “slight problems” category increased from 4 to 7% for heifers and from 2 to 3% for cows. A total of 528,475 first-calving records were analyzed with a Bayesian bivariate sire-maternal grandsire threshold liability model. Posterior means of direct and maternal heritabilities were 0.13 and 0.09 for CD, and 0.07 and 0.08 for SB, respectively. Strong genetic correlations were found between direct SB and direct CD (0.79), and between maternal SB and maternal CD (0.62), whereas all genetic correlations between direct and maternal effects within or between traits were close to zero. These positive correlations are favorable in the sense that selection for one of the traits would result in a favorable selection response for the second trait. No genetic correlations between direct and maternal effects imply that bulls should be evaluated both as sire of the calf (direct) and sire of the cow (maternal). No genetic change for SB was found, and a slight genetic improvement for CD was detected.     

Genetic analysis of herd life in Canadian dairy cattle on a lactation basis using a Weibull proportional hazards model

The objectives of this study were to identify the most important factors that influence functional survival and to estimate the genetic parameters of functional survival for Canadian dairy cattle. Data were obtained from lactation records extracted for the May 2002 genetic evaluation of Holstein, Jersey, and Ayrshire breeds that calved between July 1, 1985 and April 5, 2002. Analysis was performed using a Weibull proportional hazard model, and the baseline hazard function was defined on a lactation basis instead of the traditional analysis of the whole length of life. The statistical model included the effects of stage of lactation; season of production; the annual change in herd size; type of milk recording supervision; age at first calving; effects of milk, fat, and protein yields calculated within herd-year-parity deviations; and the random effects of herd-year-season of calving and sire. All effects fitted in the model had a significant effect on functional survival of cows in all breeds. Milk yield was by far the most important factor influencing survival, and the hazard increased as the milk production of the cows decreased. The hazard also increased as the fat content increased compared with the average group. Heifers that were older at calving were at higher risk of being culled, and expanding herds were at lower risk of being culled compared with stable herds. More culling was found in unsupervised herds than in supervised herds. The heritability values obtained were 0.14, 0.10, and 0.09 for Holstein, Jersey, and Ayrshire, respectively. Rank correlation between estimated breeding values (EBV) obtained from the current national genetic evaluation of direct herd life and the survival kit used in this study ranged from 0.65 to 0.87, depending on the number of daughters per sire. Estimated genetic trend obtained using the survival kit was overestimated.     

Estimation of intrachromosomal inbreeding depression on female fertility using runs of homozygosity in Finnish Ayrshire cattle

Inbreeding increases homozygosity, which in turn increases the frequency of harmful recessive alleles, resulting in inbreeding depression. Inbreeding depression on fertility reduces the profitability of dairy farming by decreasing the lifetime milk production of cows and by increasing insemination and veterinary costs. Continuous homozygous segments, called runs of homozygosity (ROH), are currently considered to provide an effective measure of genomic inbreeding. The aim of this study was to estimate the effect of increased intrachromosomal homozygosity for female fertility in the Finnish Ayrshire population using ROH and haplotype analysis. Genotypes were obtained from 13,712 females with the Illumina BovineLD v.2 BeadChip low-density panel (Illumina Inc., San Diego, CA) and imputed to 50K density. After quality control, 40,554 single nucleotide polymorphisms remained for the analysis. Phenotypic data consisted of records for nonreturn rate, intervals from first to last insemination (IFL), and intervals from calving to first insemination. The raw phenotypic values were preadjusted for systematic effects before statistical analyses. The ROH-based inbreeding coefficients (F_ROH) were used as covariates in the mixed model equation to estimate the association between inbreeding and inbreeding depression on female fertility. First, we estimated the effect of increased chromosomal F_ROH. We detected significant inbreeding depression on IFL. Based on our results, a 10% increase in F_ROH on chromosomes 2, 18, and 22 were associated with IFL of heifers lengthening by 1.6, 0.9, and 0.7 d, respectively. Similarly, a 10% increase in F_ROH on chromosome 15 was associated with IFL of second-parity cows increasing by 2.3 d. Next, we located the regions within the chromosomes showing inbreeding depression. Our analysis revealed regions near the beginning of chromosome 2 and toward the ends of chromosomes 15, 18, and 22 that were associated with inbreeding depression on IFL. Last, we performed a haplotype analysis for the detected regions. The most promising haplotypes of each region were associated with IFL of heifers increasing by 4.4, 3.2, and 4.1 d on chromosomes 2, 18, and 22, respectively. The haplotype on chromosome 15 associated with IFL of second-parity cows increasing by 7.6 d. Overall, the breeding program requires inbreeding control, as increased genomic inbreeding in our study was associated with reduced reproductive ability in Finnish Ayrshire cattle.     

Reproductive Performance of Crossbred and Purebred Dairy Cows

Analysis of 3095 records from purebred and crossbred dairy cows at five research stations of Agriculture Canada showed that the additive, maternal, and heterosis effects on kind of birth, placental condition, and percent of male or female dead calves were of minor importance.In 3108 records of purebred cows, the number of dead calves did not depend on whether or not the calf was purebred or crossbred or if it was born in first, second, third, or fourth lactation. However, 3080 records from cows of Holstein and Ayrshire lines and crossbred cows resulting from crossing the two lines gave results of higher mortalities of Holstein calves than of Ayrshire or crossbred cows. Holstein cows also had more abnormal births than cows in other genetic groups. Placental condition did not vary among the genetic groups of cows. Rebreeding rate, defined as percentage of cows pregnant for the second time based on the number of heifers calving for the first time, less the number of heifers culled for reasons other than reproduction, was 88% for Holstein and crossbred cows and 78% for Ayrshire cows. Reduction of cows in the herds from first to third lactation was the same for Holstein and crossbred cows (63%) but 77% for Ayrshires. Means of days to first service, number of services per conception, calving interval, and gestation period were almost identical for each genetic group of cows.     

Analysis of milk urea nitrogen and lactose and their effect on longevity in Canadian dairy cattle

The aim of this study was to assess the phenotypic level of lactose and milk urea nitrogen concentration (MUN) and the association of these traits with functional survival of Canadian dairy cattle using a Weibull proportional hazards model. A total of 1,568,952 test-day records from 283,958 multiparous Holstein cows from 4,758 herds, and 79,036 test-day records from 26,784 multiparous Ayrshire cows from 384 herds, calving from 2001 to 2004, were used for the phenotypic analysis. The overall average lactose percentage and MUN for Ayrshires were 4.49% and 12.20 mg/dL, respectively. The corresponding figures for Holsteins were 4.58% and 11.11 mg/dL. Concentration of MUN increased with parity number, whereas lactose percentage decreased in later parities. Data for survival analysis consisted of 39,536 first-lactation cows from 1,619 herds from 2,755 sires for Holsteins and 2,093 cows in 228 herds from 157 sires for Ayrshires. Test-day lactose percentage and MUN were averaged within first lactation. Average lactose percentage and MUN were grouped into 5 classes (low, medium-low, medium, medium-high, and high) based on mean and standard deviation values. The statistical model included the effects of stage of lactation, season of production, the annual change in herd size, type of milk-recording supervision, age at first calving, effects of milk, fat, and protein yields calculated as within herd-year-parity deviations, herd-year-season of calving, lactose percentage and MUN classes, and sire. The relative culling rate was calculated for animals in each class after accounting for the remaining effects included in the model. Results showed that there was a statistically significant association between lactose percentage and MUN in first lactation with functional survival in both breeds. Ayrshire cows with high and low concentration of MUN tended to be culled at a higher than average rate. Instead, Holstein cows had a linear association, with decreasing relative risk of culling with increasing levels of MUN concentration. The relationship between lactose percentage and survival was similar across breeds, with higher risk of culling at low level of lactose, and lower risk of culling at high level of lactose percentage.     

Haplotypes responsible for early embryonic lethality detected in Nordic Holsteins

Widespread use of a limited number of elite sires in dairy cattle breeding increases the risk of some deleterious allelic variants spreading in the population. Genomic data are being used to detect relatively common (frequency >1%) haplotypes that never occur in the homozygous state in live animals. Such haplotypes likely include recessive lethal or semilethal alleles. The aim of this study was to detect such haplotypes in the Nordic Holstein population and to identify causal genetic factors underlying these haplotypes. Illumina BovineSNP50 BeadChip (Illumina Inc., San Diego, CA) genotypes for 26,312 Nordic Holstein animals were phased to construct haplotypes. Haplotypes that are common in the population but never observed as homozygous were identified. Two such haplotypes overlapped with previously identified recessive lethal mutations in Holsteins—namely, structural maintenance of chromosomes 2 (HH3) and brachyspina. In addition, we identified 9 novel putative recessive lethal-carrying haplotypes, with 26 to 36 homozygous individuals expected among the genotyped animals but only 0 to 3 homozygotes observed. For 2 out of 9 homozygous-deficient haplotypes, insemination records of at-risk mating (carrier bull with daughter of carrier sire) showed reduced insemination success compared with not-at-risk mating (noncarrier bull with daughter of noncarrier sire), supporting early embryonic mortality. To detect the causative variant underlying each homozygous-deficient haplotype, data from the 1000 Bull Genome Project were used. However, no variants or deletions identified in the chromosome regions covered by the haplotypes showed concordance with haplotype carrier status. The carrier status of detected haplotypes could be used to select bulls to reduce the frequency of the latent lethal mutations in the population. If desired, at-risk matings could be avoided.     

Threshold model analysis of dystocia in dairy cattle when progeny information is limited

Progeny of 374 sires were sampled from the National Association of Animal Breeders data base to study the effect of analysis procedures and of limited progeny information on predictors of sire merit for calving ease. Situations of limited progeny information were achieved by evaluating sires by using their first 50 progeny, a random sample of 50 progeny, and a random sample of 500 progeny. Sires were evaluated by threshold model and BLUP procedures. The designed situations of limited progeny information did not result in a clear difference between procedures. Both procedures had a rank correlation of .57 between sire solutions from the first 50 and 500 progeny; the rank correlation between evaluations based on random 50 and 500 progeny was .70 and .69 for the threshold model and BLUP, respectively. Major changes in rank from random 50 to 500 progeny tended to occur among those sires with few or no calving records from matings to heifers in the random sample of 50 progeny. The BLUP sire solutions were partitioned, and a positive correlation between 500 progeny sire solutions and the partition for parity of dam indicated that easy calving progeny had sires that tended to be mated to heifers and that difficult calving progeny had sires that were mated to cows in later parities.     

Analysis of the relationship between somatic cell score and functional longevity in Canadian dairy cattle

The aim of this study was to assess the level of somatic cell count (SCC) and to explore the impact of somatic cell score (SCS) on the functional longevity of Canadian dairy cattle by using a Weibull proportional hazards model. Data consisted of 1,911,428 cows from 15,970 herds sired by 7,826 sires for Holsteins, 80,977 cows in 2,036 herds from 1,153 sires for Ayrshires, and 53,114 cows in 1,372 herds from 1,758 sires for Jerseys. Functional longevity was defined as the number of days from the first calving to culling, death, or censoring. The test-day SCC was transformed to a linear score, and the resulting SCS were averaged within each lactation. The average SCS were grouped into 10 classes. The statistical model included the effects of stage of lactation; season of production; annual change in herd size; type of milk recording supervision; age at first calving; effects of milk, fat, and protein yields, calculated as within-herd-year-parity deviations; herd-year-season of calving; SCS class; and sire. The relative culling rate was calculated for animals in each SCS class after accounting for the aforementioned effects. The overall average SCC for Holsteins was 167,000 cells/mL, for Ayrshires was 155,000 cells/mL, and for the Jerseys was 212,000 cells/mL. In all breeds there were no appreciable differences in the relative risk of culling among classes of SCS breed averages (i.e., up to a SCS of 5). However, as the SCS increased beyond the breed average, the relative risk of cows being culled increased considerably. For instance, Holstein, Ayrshire, and Jersey cows with the highest classes of SCS had, respectively, a 4.95, 6.73, and 6.62 times greater risk of being culled than cows with average SCS.     

Relationship between reproduction traits and functional longevity in canadian dairy cattle

The aim of this study was to use survival analysis to assess the relationship between reproduction traits and functional longevity of Canadian dairy cattle. Data consisted of 1,702,857; 67,470; and 33,190 Holstein, Ayrshire, and Jersey cows, respectively. Functional longevity was defined as the number of days from first calving to culling, death, or censoring; adjusted for the effect of milk yield. The reproduction traits included calving traits (calving ease, calf size, and calf survival) and female fertility traits (number of services, days from calving to first service, days from first service to conception, and days open). The statistical model was a Weibull proportional hazards model and included the fixed effects of stage of lactation, season of production, the annual change in herd size, and type of milk recording supervision, age at first calving, effects of milk, fat, and protein yields calculated as within herd-year-parity deviations for each reproduction trait. Herd-year-season of calving and sire were included as random effects. Analysis was performed separately for each reproductive trait. Significant associations between reproduction traits and longevity were observed in all breeds. Increased risk of culling was observed for cows that required hard pull, calved small calves, or dead calves. Moreover, cows that require more services per conception, a longer interval between first service to conception, an interval between calving to first service greater than 90 d, and increased days open were at greater risk of being culled.     

Influence of breed of fetus on periparturient endocrine responses and subsequent milk production of Ayrshire dams

Purebred Ayrshire females were assigned to two groups based on the breed of fetus carried during gestation. In group 1, Limousin embryos were transferred nonsurgically into Ayrshire recipients (10 heifers and 1 cow), and in group 2, 11 Ayrshire heifers and 1 cow were inseminated artificially to Ayrshire bulls. Blood samples were collected daily from d 265 of gestation until d 15 postpartum from 5 heifers of each group. Milk yield was recorded on alternate weeks during the first 20 wk postpartum. Calf birth weight was higher (44.2 vs. 35.4 kg) and gestation was longer (297.4 vs. 280.2) in Ayrshire dams bearing Limousin fetuses than in those bearing Ayrshire fetuses. Daily milk production for the first 20 wk was lower (18.1 vs. 20.8 kg) in Ayrshire dams bearing Limousin fetuses than in those bearing Ayrshire fetuses. Prepartum decrease in progesterone concentrations and increase in estrone concentrations were faster in Ayrshire heifers bearing Limousin fetuses than in those bearing Ayrshire fetuses. Profiles of peripartum concentrations of bovine placental lactogen differed between Ayrshire carrying different families of Limousin fetuses but were similar in those carrying families of Ayrshire fetuses. The concentrations of 15-keto-13,14-dihydroprostaglandin F2 alpha were lower during the postpartum period in heifers than gave birth to Limousin calves than in those that had Ayrshire calves. In conclusion, the breed of fetus influences physiological and endocrine responses of the dam, which might have some effect on milk production of the dam.     

Use of later records in dairy sire evaluation: a review

Performance in first lactation has been the standard of evaluation for most genetic studies with dairy cattle. First records are available sooner on more cows and are less susceptible to error from selection, injury, previous days dry, and mastitis than are later records. However, first records have been considerably less than perfect in predicting traits of lifetime performance, which should be the primary selection objective in dairy cattle. Later records provide additional information for more accurate sire evaluations and should be a better index of health and resistance to mastitis than first lactations. The economic importance of later records relative to first is that there are more and actual yields are higher. Herds with more older cows can reduce commitment of resources to heifer rearing, and heifers can be selected more intensely prior to first calving than herds with more cows of younger ages. Some sire evaluation systems ignore later records because of computational expense, potential selection bias, and difficulty of age adjustment. Later records may contain useful information relative to lifetime profitability of sire progeny groups. Development of proper methodology for utilizing information available in later records appears fruitful for research.