Calving difficulty and stillbirths of pure Holsteins versus crossbreds of Holstein with Normande, Montbeliarde, and Scandinavian Red

Pure Holstein cows and Normande/Holstein, Montbeliarde/Holstein, and Scandinavian Red/Holstein crossbred cows were compared for calving difficulty and stillbirth rates. Scandinavian Red was a combination of Norwegian Red and Swedish Red. All cows calved from June 2001 to August 2004 at 7 commercial dairies. Statistical models for analysis included effects of herd-year-season of calving and sex of calf in addition to breed of sire and breed group of dam. Male calves had significantly more calving difficulty and stillbirths than heifer calves. First-calf Holsteins bred to Holstein, Brown Swiss, Montbeliarde, and Scandinavian Red bulls were used to determine effects of breed of sire. Calves sired by Scandinavian Red bulls (5.5%) and Brown Swiss bulls (12.5%) had significantly less calving difficulty than calves sired by Holstein bulls (16.4%) from Holstein first-calf heifers. Also, fewer stillbirths resulted from use of Scandinavian Red bulls (7.7%) compared with use of Holstein bulls (15.1%) for first-calf Holstein heifers. Scandinavian Red-sired calves (2.1%) had significantly less calving difficulty than Holstein-sired calves (8.4%) for multiparous Holstein dams. Non-Holstein breeds of sire had significantly fewer stillbirths than Holstein sires when mated to multiparous Holstein dams. To determine the effects of breed of dam, 676 pure Holsteins, 262 Normande/Holstein, 370 Montbeliarde/Holstein, and 264 Scandinavian Red/Holstein crossbred virgin heifers that had been bred to Brown Swiss, Montbeliarde, and Scandinavian Red bulls were utilized. All groups of crossbred cows had significantly less calving difficulty at first calving than pure Holsteins (3.7 to 11.6% vs. 17.7%). Furthermore, Montbeliarde/Holstein (6.2%) and Scandinavian Red/Holstein (5.1%) crossbreds had significantly lower stillbirth rates at first calving than pure Holsteins (14.0%).     

Influence of genetic differences in merit of mates on sire evaluation

Effect of nonrandomness of bulls' mates on daughter milk yield was examined from first lactation records of cows with birth dates in 1965 and later. Results were based on 67,081 Ayrshire, 77,633 Brown Swiss, 241,486 Guernsey, 1,433,761 Holstein, 291,201 Jersey, and 10,465 Milking Shorthorn records. Extent of assortative mating was examined. Correlations between sire Predicted Difference and dam (mate) Cow Index for individual years ranged from -.08 to .20. Correlations for all records within herd-year (.00 to .02) indicated essentially no assortative mating for milk yield for any breed except Ayrshire. For Ayrshires, negative assortative mating was indicated by a correlation of -.07. Within-sire regressions of daughter milk yield deviated from contemporary average (which had been adjusted for average Predicted Difference of contemporaries' sires) on dam Cow Index (merit of mates) by breed were .84 to 1.08. Expected regression was 1.00. Effect of merit of mates on sire evaluation was determined by comparing evaluations from standardized yield with those from standardized yield minus dam Cow Index. Correlations between evaluations for 4233 Ayrshire, 5275 Brown Swiss, 13,742 Guernsey, 32,572 Holstein, 13,688 Jersey, and 1240 Milking Shorthorn bulls rounded to 1.00 except for Milking Shorthorns (.99); average absolute differences in evaluations were 9 to 16 kg, and maximum differences were 49 to 118 kg. Adding an adjustment to Sire Summaries to account for nonrandomness of mates would do little to increase accuracy.     

Marker selection and genomic prediction of economically important traits using imputed high-density genotypes for 5 breeds of dairy cattle

Marker sets used in US dairy genomic predictions were previously expanded by including high-density (HD) or sequence markers with the largest effects for Holstein breed only. Other non-Holstein breeds lacked enough HD genotyped animals to be used as a reference population at that time, and thus were not included in the genomic prediction. Recently, numbers of non-Holstein breeds genotyped using HD panels reached an acceptable level for imputation and marker selection, allowing HD genomic prediction and HD marker selection for Holstein plus 4 other breeds. Genotypes for 351,461 Holsteins, 347,570 Jerseys, 42,346 Brown Swiss, 9,364 Ayrshires (including Red dairy cattle), and 4,599 Guernseys were imputed to the HD marker list that included 643,059 SNP. The separate HD reference populations included Illumina BovineHD (San Diego, CA) genotypes for 4,012 Holsteins, 407 Jerseys, 181 Brown Swiss, 527 Ayrshires, and 147 Guernseys. The 643,059 variants included the HD SNP and all 79,254 (80K) genetic markers and QTL used in routine national genomic evaluations. Before imputation, approximately 91 to 97% of genotypes were unknown for each breed; after imputation, 1.1% of Holstein, 3.2% of Jersey, 6.7% of Brown Swiss, 4.8% of Ayrshire, and 4.2% of Guernsey alleles remained unknown due to lower density haplotypes that had no matching HD haplotype. The higher remaining missing rates in non-Holstein breeds are mainly due to fewer HD genotyped animals in the imputation reference populations. Allele effects for up to 39 traits were estimated separately within each breed using phenotypic reference populations that included up to 6,157 Jersey males and 110,130 Jersey females. Correlations of HD with 80K genomic predictions for young animals averaged 0.986, 0.989, 0.985, 0.992, and 0.978 for Jersey, Ayrshire, Brown Swiss, Guernsey, and Holstein breeds, respectively. Correlations were highest for yield traits (about 0.991) and lowest for foot angle and rear legs–side view (0.981and 0.982, respectively). Some HD effects were more than twice as large as the largest 80K SNP effect, and HD markers had larger effects than nearby 80K markers for many breed-trait combinations. Previous studies selected and included markers with large effects for Holstein traits; the newly selected HD markers should also improve non-Holstein and crossbred genomic predictions and were added to official US genomic predictions in April 2020.     

Economic merit of crossbred and purebred US dairy cattle

Heterosis and breed differences were estimated for milk yield traits, somatic cell score (SCS), and productive life (PL), a measure of longevity. Yield trait data were from 10,442 crossbreds and 140,421 purebreds born since 1990 in 572 herds. Productive life data were from 41,131 crossbred cows and 726,344 purebreds born from 1960 through 1991. The model for test-day yields and SCS included effects of herd-year-season, age, lactation stage, regression on sire's predicted transmitting ability, additive breed effects, heterosis, and recombination. The model for PL included herd-year-season, breed effects, and general heterosis. All effects were assumed to be additive, but estimates of heterosis were converted to a percentage of the parent breed average for reporting. Estimates of general heterosis were 3.4% for milk yield, 4.4% for fat yield, and 4.1% for protein yield. A coefficient of general recombination was derived for multiple-breed crosses, but recombination effects were not well estimated and small gains, not losses, were observed for yield traits in later generations. Heterosis for SCS was not significant. Estimated heterosis for PL was 1.2% of mean productive life and remained constant across the range of birth years. Protein yield of Brown Swiss x Holstein crossbreds (0.94 kg/d) equaled protein yield of purebred Holsteins. Fat yields of Jersey x Holstein and Brown Swiss x Holstein crossbreds (1.14 and 1.13 kg/d, respectively) slightly exceeded that of Holsteins (1.12 kg/d). With cheese yield pricing and with all traits considered, profit from these crosses exceeded that of Holsteins for matings at breed bases. For elite matings, Holsteins were favored because the range of evaluations is smaller and genetic progress is slower in breeds other than Holstein, in part because fewer bulls are sampled. A combined national evaluation of data for all breeds and crossbreds may be desirable but would require an extensive programming effort. Animals should receive credit for heterosis when considered as mates for another breed.     

Effects of breed and region on longevity traits through five years of age in Brown Swiss, Holstein, and Jersey cows in the United States

The objective of this study was to assess breed, and breed × region interactions for several longevity-related traits, measured up to 5 yr of age in Brown Swiss, Holstein, and Jersey cows in 7 regions of the United States. Data were analyzed using logistic, poisson, and linear models, and survival analyses. The traits were stayability (yes/no survived to 5 yr of age), number of completed lactations, days lived, herd-life, and days in milk (DIM) to 5 yr of age. Probable lifetime DIM were also estimated using data from the first 5 yr of age of the cows. Herd-life was defined as the days lived up to 5 yr of age minus the age at first calving. Days in milk consisted of herd-life up to 5 yr of age minus the dry periods. Three data files were analyzed: herds with one breed of cows, herds with Holstein and Brown Swiss, and herds with Holstein and Jersey cows. Breed × region interaction was usually significant, with larger effects for the southern regions. Jerseys obtained largest values for the ratio of DIM to days lived, and for the number of completed lactations to 5 yr of age. Brown Swiss had the largest probabilities of surviving to 5 yr of age (stayabilities) in all regions. For the other traits, the results for Brown Swiss were inconsistent, but usually the cows of this breed had shorter herd-life and DIM to 5 yr of age than Holsteins. Brown Swiss cows were expected to have more total DIM in their lifetime in the Southeast than Holsteins. Survival analysis gave the most readily interpretable information, although the linear, poisson, and logistic analyses answered slightly different questions. Adjustment for herd size did not modify the results.     

Differences in modified contemporary comparison sire evaluations from first and later lactations by breed

Sire evaluations from three sets of daughter records, first records only (first), later records after firsts (later), and all records (all) by Modified Contemporary Comparison procedures were used to examine differences in first and later lactation evaluations by breed. January 1984 evaluations for milk for 767 Ayrshires, 3,175 Guernsey, 29,498 Holstein, 3,530 Jersey, and 984 Brown Swiss bulls with 10 or more daughters in each set were used. Average differences between evaluations (later minus first) were 36, 0, 6, 35, and 35 kg milk for Ayrshire, Guernsey, Holstein, Jersey, and Brown Swiss bulls. Standard deviations of the difference were 114, 94, 142, 91, and 134 kg, showing considerable sire-to-sire variation in difference. Correlations between evaluations based on first and later records were .84 to .86 for all breeds except .92 for Jerseys. Percent of first lactations culled was correlated .20, .18, .16, .16, and .19 with difference for Ayrshire, Guernsey, Holstein, Jersey, and Brown Swiss, indicating that culling produced larger differences between evaluations for first and later lactations in favor of later evaluations. Prediction of sire evaluation from later records was enhanced by knowledge of sire's age in addition to first evaluation for Guernsey, Holstein and Jersey sires. In these breeds, for a constant first evaluation, and percent culled in first lactation, younger bulls had higher evaluations from later records. This study showed important differences between evaluations from first and later records for all breeds.     

Comparisons of Holsteins with Brown Swiss and Jersey cows on the same farm for age at first calving and first calving interval

Our objective was to evaluate breed differences for heat-stress resistance as reflected by age at first calving and first calving interval. We examined the effect of geographic location and birth season on age at first calving, and geographic location and first calving season on first calving interval on Holsteins and Jerseys, and Holsteins and Brown Swiss located on the same farm. We defined 7 regions within the United States: Northwest, Central north, Northeast, Central, Central south, Southwest, and Southeast, and analyzed 7 individual states: Ohio, Wisconsin, Oregon, California, Arizona, Texas, and Florida. Brown Swiss were older than Holsteins at first calving (833 +/- 2.4 vs. 806 +/- 2.0 d in regions, and 830 +/- 3.1 vs. 803 +/- 2.4 d in states), but Holsteins and Brown Swiss did not differ for first calving interval. Jerseys were younger than Holsteins at first calving and had shorter first calving intervals. In data from individual states, Holsteins housed with Brown Swiss were older at first calving than were Holsteins housed with Jerseys (800 +/- 2.7 vs. 780 +/- 2.5 d). Holsteins housed with one breed or the other were analyzed as a separate data set, and referred to as "type of Holstein." The interaction of "type of Holstein" with first calving season was highly significant for first calving interval. Geographic location and season effects were smaller for Jerseys than for Holsteins; thus, Jerseys showed evidence of heat-stress resistance with respect to Holsteins. Management modified age at first calving in Holsteins to more nearly match that of the other breed. Longer calving intervals might be partly due to voluntary waiting period to breed the cows.     

Variation in fat globule size in bovine milk and its prediction using mid-infrared spectroscopy

The objectives of this study were to investigate the sources of variation in milk fat globule (MFG) size in bovine milk and its prediction using mid-infrared (MIR) spectroscopy. Mean MFG size was measured in 2,076 milk samples from 399 Ayrshire, Brown Swiss, Holstein, and Jersey cows, and expressed as volume moment mean (D[4,3]) and surface moment mean (D[3,2]). The mid-infrared spectra of the samples and milk performance data were also recorded during routine milk recording and testing. The effects of breed, herd nested within breed, days in milk, season, milking period, age at calving, parity, and individual animal on the variation observed in MFG size were investigated. Breed, herd nested within breed, days in milk, season, and milking period significantly affected mean MFG size. Milk fat globule size was the largest at the beginning of lactation and subsequently decreased. Milk samples with the smallest MFG on average came from Holstein cows, and those with the largest were from Jersey and Brown Swiss cows. Partial least squares regression was used to predict MFG size from MIR spectra of samples with a calibration data set containing 2,034 and 2,032 samples for D[4,3] and D[3,2], respectively. Coefficients of determination of cross validation for D[4,3] and D[3,2] prediction models were 0.51 and 0.54, respectively. The associated ratio of performance deviation values were 1.43 and 1.48 for D[4,3] and D[3,2], respectively. With these models, individual mean MFG size could not be accurately predicted, but results may be sufficient to screen samples for having either small or large MFG on average. Significant but low correlations of D[4,3] and D[3,2] with milk fat yield were estimated (0.16 and 0.21, respectively). Significant and moderate Pearson correlation coefficients for fat percent with D[4,3] and D[3,2] were assessed (0.34 and 0.36, respectively). This correlation was greater between milk fat percentage and predicted MFG size than with measured MFG size with coefficients of 0.47 and 0.49 for D[4,3] and D[3,2], respectively. The MIR prediction equations are potentially overusing the correlation between fat and MFG size and exploiting the strong relationship between the MIR spectra and total milk fat. However, the predictions of MFG size are able to determine variation in mean globule size beyond what would be achieved just by looking at the correlation with fat production.     

Relationships between reproduction traits, age and body weight at calving, and days dry in first lactation Ayrshires and Holsteins

Individual cow test day records collected between December 1979 and June 1986 were used to calculate measures of reproductive performance, age and weight at calving, and days dry for 7824 Ayrshire and 79,755 Holstein cows in first lactation. Separate analyses by breed were carried out according to a multiple-trait mixed model. Sixty-two Ayrshire and 369 Holstein sires were treated as random in the analyses. Ayrshires were, on average, older and lighter at calving than Holsteins, but the breeds differed little in reproduction measures and days dry. Heritabilities of fertility traits, days to first breeding, days open, and services per conception were all less than .015 in the multi-trait analyses. With the exception of body weight, heritability estimates for the other traits were less than .05. Phenotypic correlations between traits were almost identical for the two breeds, and genetic correlations tended to be similar. Exceptions involved the trait days to first breeding and services per conception, but heritabilities of these traits were close to zero (p less than .008) in Ayrshires. Fertility traits were positively correlated genetically. Genetic correlations between days open and both age and body weight at calving were small. The genetic correlation between age and weight at calving was -.90 and -.68 in Ayrshires and Holsteins, respectively. Genetic correlations between days dry and all traits except body weight were moderate and positive.     

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.     

Genomic characterization of autozygosity and recent inbreeding trends in all major breeds of US dairy cattle

Maintaining a genetically diverse dairy cattle population is critical to preserving adaptability to future breeding goals and avoiding declines in fitness. This study characterized the genomic landscape of autozygosity and assessed trends in genetic diversity in 5 breeds of US dairy cattle. We analyzed a sizable genomic data set containing 4,173,679 pedigreed and genotyped animals of the Ayrshire, Brown Swiss, Guernsey, Holstein, and Jersey breeds. Runs of homozygosity (ROH) of 2 Mb or longer in length were identified in each animal. The within-breed means for number and the combined length of ROH were highest in Jerseys (62.66 ± 8.29 ROH and 426.24 ± 83.40 Mb, respectively; mean ± SD) and lowest in Ayrshires (37.24 ± 8.27 ROH and 265.05 ± 85.00 Mb, respectively). Short ROH were the most abundant, but moderate to large ROH made up the largest proportion of genome autozygosity in all breeds. In addition, we identified ROH islands in each breed. This revealed selection patterns for milk production, productive life, health, and reproduction in most breeds and evidence for parallel selective pressure for loci on chromosome 6 between Ayrshire and Brown Swiss and for loci on chromosome 20 between Holstein and Jersey. We calculated inbreeding coefficients using 3 different approaches, pedigree-based (F_PED), marker-based using a genomic relationship matrix (F_GRM), and segment-based using ROH (F_ROH). The average inbreeding coefficient ranged from 0.06 in Ayrshires and Brown Swiss to 0.08 in Jerseys and Holsteins using F_PED, from 0.22 in Holsteins to 0.29 in Guernsey and Jerseys using F_GRM, and from 0.11 in Ayrshires to 0.17 in Jerseys using F_ROH. In addition, the effective population size at past generations (5–100 generations ago), the yearly rate of inbreeding, and the effective population size in 3 recent periods (2000–2009, 2010–2014, and 2015–2018) were determined in each breed to ascertain current and historical trends of genetic diversity. We found a historical trend of decreasing effective population size in the last 100 generations in all breeds and breed differences in the effect of the recent implementation of genomic selection on inbreeding accumulation.     

Comparison of dairy beef genetics and dietary roughage levels

The objectives of these trials were to investigate the performance of Jersey steers in relation to Holsteins under current management practices when fed diets differing in energy density and subsequent effects on carcass characteristics. In experiment 1, twelve Jersey and 12 Holstein steers were offered dietary treatments with differing roughage levels. Roughage levels investigated on a dry matter basis were 55% reduced to 25% versus 25% followed by 12.5% (HIGH and LOW, respectively) with all animals receiving the same finishing diet containing 6.5% roughage. Holstein steers were heavier than Jerseys at the initiation of the trial (228 vs. 116 kg). A diet response was observed for gain efficiency during the first period in which LOW was greater than HIGH. Holstein steers had higher dry matter intakes and rates of gain than Jerseys. However, gain efficiency was better for Jersey steers during the first and last periods. Carcass traits were influenced by breed but not diet. Holsteins had heavier hot carcass weights, greater dressing percentages, more backfat, and larger longissimus muscle area, whereas marbling scores were similar to Jerseys. The increased efficiency of Jersey steers and significant reduction in carcass value due to light carcass weights suggested that Jersey steers should be fed to heavier live weights. Experiment 2 utilized 85 steers to investigate continuous feeding of a low-roughage, high-concentrate diet versus a phase-feeding strategy. Jersey (n = 40) and Holstein (n = 45) steers were assigned to a diet containing 20% corn silage on a dry matter basis (HEN) or a phase-feeding program (PHASE) in which corn silage was reduced from 60 to 40% followed by the same diet as HEN. Initial body weights were similar for dietary treatments but differed by breed. A diet response was observed for live weight at the end of the first and second period, first period average daily gain (ADG), overall ADG, and days on feed with HEN having higher ADG than PHASE and fewer days on feed. Breed affected all body weight and gain variables with Holsteins being heavier and gaining more rapidly than Jersey steers. Jersey carcasses were lighter, had the highest percentage trim loss, least amount of backfat, and lowest numerical yield grade. Holstein steers had a greater propensity for gain, whereas the Jersey steers were equally or more efficient. These findings suggest that phase feeding Jersey steers higher-roughage diets has minimal effect on carcass traits.     

Factors associated with colostral specific gravity in dairy cows

The objectives of this study were to identify factors associated with colostral specific gravity in dairy cows, as measured by a commercially available hydrometer (Colostrometer). Colostral specific gravity was measured in 1085 first-milking colostrum samples from 608 dairy cows of four breeds on a single farm during a 5-yr period. Effects of breed, lactation number, and month and year of calving on colostral specific gravity were determined, as were correlations between colostral specific gravity, nonlactating period length, and 305-d yields of milk, protein, and fat. For 75 multiparous Holstein cows, relationships between colostral specific gravity, colostral IgG1, protein, and fat concentrations, and season of calving were determined. Colostral specific gravity values were lower for Brown Swiss and Ayrshire cows than for Jersey and Holstein cows, and lower for cows entering first or second lactation than third or later lactations. Month of calving markedly affected colostral specific gravity values, with highest values occurring in autumn and lowest values in summer. In multiparous Holstein cows, colostral specific gravity was more strongly correlated with colostral protein concentration (r = 0.76) than IgG1 concentration (r = 0.53), and colostral protein concentration varied seasonally (higher in autumn than summer). Our results demonstrate that colostral specific gravity more closely reflects colostral protein concentration than IgG1 concentration and is markedly influenced by month of calving. These results highlight potential limitations of using colostral specific gravity as an indicator of IgG1 concentration.     

Results of a producer survey regarding crossbreeding on US dairy farms

Comprehensive surveys were sent to 528 US dairy producers who are currently practicing crossbreeding in their herds. Fifty usable surveys were returned, and the resulting data included qualitative responses regarding facilities, milk recording plans, milk pricing, crossbreeding goals, breed selection, advantages, disadvantages, and future plans. Quantitative variables included producer scores on a 1 to 5 scale for questions regarding ability to fit into the free stalls and milking parlor, milk volume, component percentages, involuntary culling rate, conception rate, calving difficulty, calf mortality, and prices for breeding stock, cull cows, market steers, and bull calves. The most common first generation crosses involved Jersey and Brown Swiss bulls mated to Holstein cows, and backcrosses to one of these parental breeds were most common in the next generation. Producers who responded to this survey desired, and indicated that they achieved, improvements in fertility, calving ease, longevity, and component percentages through crossbreeding. Respondents indicated that crosses involving the Jersey and Brown Swiss breeds had a clear advantage in longevity relative to purebred Holsteins, and conception rates for crosses of Jersey or Brown Swiss sires on Holstein cows were similar to the (high) conception rates typically achieved in purebred Jersey matings. Respondents also indicated that milk composition was improved in the crossbred cattle, but producers cited some difficulties in marketing crossbred breeding stock and bull calves, and noted that the lack of uniformity within the milking herd created management challenges. Based on results of this survey, it appears that crossbreeding can improve the health, fertility, longevity, and profitability of commercial dairy cattle. However, further research is needed regarding specific heterosis estimates for functional traits in crosses involving each of the major dairy breeds, and improvements are needed in systems for recording the ancestry and breed composition of crossbred animals.     

Multitrait estimation of relationships of first-lactation yields to body weight changes in Holstein heifers

An experimental population of 994 Holstein heifers from 56 sires was used to estimate simultaneously heritabilities and genetic and phenotypic correlations between first-lactation yields and prepartum and postpartum weight changes. Variance and covariance components were estimated by the multitrait restricted maximum likelihood method. Heritability estimates were .09, .15, and .32 for first-lactation milk, protein, and fat yields. Heritability estimates ranged from .20 to .34 for prepartum and postpartum body weights and weight changes of first lactation. Weight gain from 350 to 462 d of age was highly correlated, genetically and phenotypically, with first-lactation milk, protein, and fat yields. Genetic and phenotypic correlations between first-lactation yields and body weights at calving and at 56, 112, 168, 224, and 280 d postpartum were positive, suggesting that the larger heifers had higher lactation yields. In contrast, genetic and phenotypic correlations between yields and weight gains during the first lactation were negative, indicating that high-producing heifers gained less weight during lactation than low-producing heifers. Heifers lost an average of 23 kg from calving to 56 d postpartum and gained weight thereafter. On genetic and phenotypic scales, larger heifers at first calving lost more weight from calving to 56 d postpartum and gained less weight from 56 d postpartum onward than smaller heifers.     

Multibreed genomic evaluations using purebred Holsteins, Jerseys, and Brown Swiss

Multibreed models are currently used in traditional US Department of Agriculture (USDA) dairy cattle genetic evaluations of yield and health traits, but within-breed models are used in genomic evaluations. Multibreed genomic models were developed and tested using the 19,686 genotyped bulls and cows included in the official August 2009 USDA genomic evaluation. The data were divided into training and validation sets. The training data set comprised bulls that were daughter proven and cows that had records as of November 2004, totaling 5,331Holstein, 1,361 Jersey, and 506 Brown Swiss. The validation data set had 2,508Holstein, 413 Jersey, and 185 Brown Swiss bulls that were unproven (no daughter information) in November 2004 and proven by August 2009. A common set of 43,385 single nucleotide polymorphisms (SNP) was used for all breeds. Three methods of multibreed evaluation were investigated. Method 1 estimated SNP effects separately within breed and then applied those breed-specific SNP estimates to the other breeds. Method 2 estimated a common set of SNP effects from combined genotypes and phenotypes of all breeds. Method 3 solved for correlated SNP effects within each breed estimated jointly using a multitrait model where breeds were treated as different traits. Across-breed genomic predicted transmitting ability (GPTA) and within-breed GPTA were compared using regressions to predict the deregressed validation data. Method 1 worked poorly, and coefficients of determination (R(2)) were much lower using training data from a different breed to estimate SNP effects. Correlations between direct genomic values computed using training data from different breeds were less than 30% and sometimes negative. Across-breed GPTA from method 2had higher R(2) values than parent average alone but typically produced lower R(2) values than the within-breed GPTA. The across-breed R(2) exceeded the within-breed R(2) for a few traits in the Brown Swiss breed, probably because information from the other breeds compensated for the small numbers of Brown Swiss training animals. Correlations between within-breed GPTA and across-breed GPTA ranged from 0.91 to 0.93. The multibreed GPTA from method 3 were significantly better than the current within-breed GPTA, and adjusted R(2) for protein yield (the only trait tested for method 3) were highest of all methods for all breeds. However, method 3 increased the adjusted R(2) by only 0.01 for Holsteins, ≤0.01 for Jerseys, and 0.01 for Brown Swiss compared with within-breed predictions.     

Trends in calving ages and calving intervals for dairy cattle breeds in the United States

Trends since 1980 for calving age and calving interval, 2 factors that influence herd life, were examined by parity for 5 breeds of US dairy cattle. Calving data were from cows with records that passed edits for USDA genetic evaluations and were in herds that remained on Dairy Herd Improvement test. First-calf heifers calved at progressively younger ages over time, but the age decline was less for later parities because of longer calving intervals. Breed differences for calving age were evident for all parities; current mean age at first calving ranged from 24 mo for Jerseys to 28 mo for Ayrshires. Mean calving age across all parities declined over time for all breeds, primarily because of increased turnover rate, and ranged from 48 mo for Holsteins to 54 mo for Ayrshires. Across parity, annual increase in calving interval was reasonably consistent (0.90 to 1.07 d/yr) for all breeds except Jersey (0.49 d/yr). Within parity, regressions of calving interval on year were generally similar to overall breed trend. Breed means for first calving interval across time ranged from 390 d for Jerseys to 407 d for Brown Swiss.     

Brown Swiss × Holstein crossbreds compared with pure Holsteins for calving traits, body weight, backfat thickness, fertility, and body measurements

Brown Swiss × Holstein crossbred cows and pure Holstein cows were compared in a designed experiment. All cows were housed in a freestall barn at the experimental station of the federal state of Saxony-Anhalt, Germany, and calved from July 2005 to August 2008. Brown Swiss × Holstein crossbred cows were mated to Holstein AI bulls for first calving and mated to Fleckvieh artificial insemination (AI) bulls for second and third calvings. Pure Holstein cows were consistently mated to Holstein AI bulls. At first calving, Holstein-sired calves from Brown Swiss × Holstein crossbred dams (282 d) had longer gestation length than Holstein-sired calves from Holstein dams (280 d). For second and third calvings, gestation length was significantly longer for Fleckvieh-sired calves from Brown Swiss × Holstein crossbred dams (284 d) than for Holstein-sired calves from Holstein dams (278 d). Holstein-sired calves from Brown Swiss × Holstein crossbred dams (43 kg) and Holstein-sired calves from pure Holstein dams (42 kg) were not significantly different for calf weight at birth for first calving. For second and third calvings, Fleckvieh-sired calves from Brown Swiss × Holstein crossbred dams (50 kg) had significantly heavier calf weight at birth than Holstein-sired calves from pure Holstein dams (44 kg). For calving difficulty and stillbirth, Brown Swiss × Holstein crossbred cows were not different from pure Holstein cows at first calving or at second and third calving. Brown Swiss × Holstein crossbred cows (71 d) were not significantly different from pure Holstein cows (75 d) for days to first breeding during first lactation; however, Brown Swiss × Holstein crossbred cows (81 d) had significantly fewer days to first breeding than pure Holstein cows (89 d) during second lactation, and the crossbred cows (85 d) tended to have fewer days to first breeding than pure Holstein cows (92 d) during third lactation. For days open, Brown Swiss × Holstein crossbred cows were not significantly different than pure Holstein cows during any of the first 3 lactations. For body weight, Brown Swiss × Holstein crossbred cows were significantly heavier than pure Holstein cows during first lactation (621 kg versus 594 kg) and second lactation (678 kg versus 656 kg). Also, Brown Swiss × Holstein crossbred cows (18.20 mm) had significantly more backfat thickness than pure Holstein cows (15.81 mm) during first lactation. Brown Swiss × Holstein crossbred cows (48 cm) had significantly greater chest width than pure Holstein cows (46 cm). Furthermore, Brown Swiss × Holstein crossbred cows had significantly longer front heel walls (5.2 cm versus 5.0 cm), significantly longer rear heel walls (4.2 cm versus 4.0 cm), and significantly more depth of the front heel (4.4 cm vs. 4.1 cm) than pure Holstein cows. This study has shown that F₁ of Brown Swiss × Holstein cows are competitive with pure Holstein cows for all traits analyzed here. For fertility, crossbred Brown Swiss × Holstein cows exhibited fewer days to first breeding during second lactation than pure Holstein cows.     

Genetic polymorphism of the epithelial mucin, PAS-I, in milk samples from the major dairy breeds.

Genetic polymorphism in a mucin of the human milk fat globule arises from variable numbers of a tandemly repeated amino acid sequence. As a consequence, the gene from each parent expresses a variable-sized protein. This is manifest on SDS gels in the form of either one or, more often, two protein bands, which differ among individuals in mobility. Evidence of such polymorphism in the bovine mucin, PAS-I, was first obtained from Holstein milk samples. The objective of this study was to evaluate the other major dairy breeds for polymorphism of their PAS-I. Milk samples from individual Jerseys, Guernseys, Ayrshires, and Brown Swiss were analyzed by SDS-PAGE. Bands of the mucin varying in number and mobility were seen in samples from all four breeds. In three of the breeds (Ayrshire, Brown Swiss, and Jersey), there was evidence that two alleles for PAS-I may have become predominant, possibly through degeneration in the structure of their tandem repeats, one that gives rise to a faster moving mucin (relative molecular weight 170,000) and the other to a slower form (relative molecular weight 200,000). In contrast, the PAS-I band patterns on SDS gels for both Guernseys and Holsteins were characterized in nearly 50% of samples by two close bands near the 205,000-molecular weight marker. This pattern was never seen in the other three breeds. The findings suggest a genetic kinship among the Ayrshire, Brown Swiss, and Jersey, on the one hand, and between the Holstein and Guernsey, on the other.