Timeliness and effectiveness of progeny testing through artificial insemination

Progeny-test (PT) programs of US artificial-insemination (AI) organizations were examined to determine timeliness of sampling, PT daughter distribution, rate of return of PT bulls to widespread service, and genetic merit of PT bulls compared with AI-proven and natural-service (NS) bulls. Bull age at semen release and at birth and calving of PT daughters was documented by breed (Ayrshire, Brown Swiss, Guernsey, Holstein, Jersey, and Milking Shorthorn) for bulls that entered AI service since 1960. Mean Holstein bull age at semen release (16 mo) changed little over time, but standard deviations (SD) decreased from 4.0 mo during the 1960s to 2.4 mo during the 1990s. Most Holstein bulls (80%) had semen released by 18 mo. Mean age of Holstein bulls at birth and calving of PT daughters during the 1990s was 29 and 56 mo, respectively (a decline of 4 mo from the 1960s); SD decreased from 6 to 3 mo. Bulls of other breeds usually were older at birth and calving of PT daughters, and SD were larger. Mean Holstein bull age when 80% of PT daughters had been born declined from 36 mo during the 1960s to 31 mo during the early 1990s; for other breeds, bulls showed the same trend but at older ages. Mean Holstein bull age when 80% of PT daughters had calved declined from 65 mo during the 1960s to 59 mo during the 1990s; for other breeds, bulls were older. Percentage of herds with PT daughters has increased over time. For Holsteins, herds with five or more usable first-parity records that had PT daughters with usable records increased from 15% during 1965 to 61% during 1998; percentage of herds with from 1 to 19% PT records increased from 11 to 38%, and percentage of herds with >50% PT daughters increased from 1 to 5%. Percentage of Holstein PT bulls returned to AI service declined to about 12% for bulls with PT entry around 1990; for other breeds, 12 to 23% of most recent PT bulls were returned to service. Percentage of milking daughters that had records usable for genetic evaluation that were sired by PT bulls increased steadily from 10 to 18%, whereas percentage of daughters with usable records that were sired by NS bulls declined from 14 to 7%. Milk yield of daughters of AI-proven bulls was 107 to 200 kg greater than for daughters of PT bulls and 366 to 444 kg greater than for daughters of NS bulls for all years. More extensive and rapid sampling and increased selection intensity of PT programs have led to more rapid genetic progress. More extensive use of AI could increase US producer income by millions of dollars annually.     

Progeny testing and selection intensity for Holstein bulls in different countries

International Bull Evaluation Service (Interbull) Holstein evaluations from February 1995 through February 2003 were used to determine characteristics of progeny testing for Holstein bulls in Australia, Canada, Denmark, France, Germany, Italy, New Zealand, Sweden, The Netherlands, and the United States. The decision to graduate a bull from progeny test (PT) was assumed to have been made based on the second Interbull evaluation, and graduation was defined as the addition of 200 daughters in the period 2.5 to 4.5 yr later. Mean bull age at PT decision varied across countries by 12 mo. Mean numbers of herds and daughters ranged from 39 to 111 and 54 to 144, respectively. Countries with higher requirements for official evaluations generally had more herds and daughters but older bulls at PT decision. Mean estimated breeding values for yield traits of sires of tested bulls were most similar across countries for fat, differing by only 6.4 kg. The four countries highest for sire protein differed only by 1 kg; however, the range was 12 kg. Percentages of bulls graduated ranged from 4.4 to 14.7 across countries. Selection intensities (standardized selection differentials) tended to be about 1.0 for yield traits. Selection intensities for somatic cell score were generally unfavorable, reflecting selection for negatively correlated yield traits. Reflecting variation in national breeding goals, selection intensities for stature were positive for most countries and highly negative for New Zealand. Selection intensity for fore udder was generally the lowest among the traits examined. All but one country showed positive selection for udder support. These statistics permit comparison of the components of PT programs across country, illustrating possible opportunities for improvement.     

Accuracy of foreign dairy bull evaluations in predicting United States evaluations for yield

Combining foreign daughter data with domestic information in dairy bull genetic evaluations has been shown to improve prediction of future domestic evaluations for US bulls. This study focused on the accuracy of Interbull evaluations of bulls with only foreign daughters, in predicting the latest domestic evaluations (based on US daughters). August 2003 USDA evaluations based only on US daughters were matched with the most recent February or August Interbull evaluations without US daughters. A minimum reliability of at least 80% for yield and 70% for somatic cell score (SCS) was required in both evaluations. This provided pairs of evaluations based on different daughters (foreign or US) for 286 bulls (60 bulls for SCS). Mean Interbull reliabilities on the US scale were 88% for yield and 84% for SCS, and the mean US reliability for the current evaluations was 91% for yield and 80% for SCS. Correlations between the Interbull and domestic evaluations were 0.90, 0.87, 0.90, and 0.87 for milk, fat, protein, and SCS respectively. Expected correlations were 0.89 for yield and 0.82 for SCS. Mean differences between the Interbull and current domestic evaluations were near zero. These foreign bulls had graduated from progeny test programs (selected for positive Mendelian sampling) before being marketed in the United States. Thus, parent average was a substantial underestimate of merit. The small average differences between evaluations from foreign and US daughters and high correlations indicate that Interbull evaluations based solely on foreign daughters are useful predictors of the US evaluations for yield and SCS, providing accuracy in agreement with reliabilities and much better estimates than the alternative, parent averages.     

Consistency of maturity rate for milk yield across countries and generations

Differences among bulls in maturity rate of their daughters for milk yield were investigated. Milk records for US Holsteins with first-parity calving dates between 1960 and 1998 were used to calculate 3 evaluations for bulls based on daughter records from parity 1, parities 1 and 2, and parities 1, 2, and 3. The 3 evaluations were used to estimate parity-specific evaluations for parities 2 and 3. Maturity rate of Holstein bull daughters in Canada and the Netherlands was compared with that for daughters of the same bulls in the United States by using official November 2004 Canadian and August 2005 Dutch parity-specific evaluations. For bulls with ≥500 first-parity daughters, correlations among parity-specific evaluations within country and birth year of bull were 0.88 between parities 1 and 2, 0.84 between parities 1 and 3, and 0.96 between parities 2 and 3 for the United States; 0.90, 0.86, and 0.97, respectively, for Canada; and 0.92, 0.89, and 0.98, respectively, for the Netherlands. Correlations between Canada and the United States for within-country differences between evaluations for parities 1 and 2 were 0.72 for bulls with ≥50 first-parity daughters and 0.89 for bulls with ≥500 first-parity daughters; corresponding correlations between the Netherlands and the United States were 0.66 and 0.82. Correlations between countries for differences between evaluations for parities 1 and 3 were slightly less, and corresponding correlations between evaluations for parities 2 and 3 were still lower. To establish whether differences between parity-specific evaluations were genetic, comparisons were made across a generation. Coefficients for regression of son on sire within country and birth years of sire and son for parity-specific evaluations and differences between parity-specific evaluations ranged from 0.35 to 0.53, with standard errors of ≤0.04. Differences in maturity rate of bull daughters were quite consistent across country, and those differences were transmitted to the sons’ daughters. Modeling to account for maturity differences should increase the accuracy of US evaluations and reduce fluctuation between evaluations, especially for bulls with daughters that deviate substantially from the population mean for maturity rate for milk yield.     

Impact of maturity rate of daughters on genetic ranking of Holstein bulls

If genetic evaluations are calculated with a single-trait repeatability model, evaluation changes may be attributed in part to bulls that have daughters that deviate considerably from the typical response to aging. Differences in maturity rate of bull daughters were examined to determine whether they influence change in bull evaluations. Standardized milk records for Holsteins that first calved between 1960 and 1998 were used to calculate 12 tailored predicted transmitting abilities (PTA) for each bull. Predicted transmitting abilities were tailored from combinations of 4 annual cut-off dates and 3 parities. Date screening selected cows first calving before January of 1996, 1997, 1998, or 1999. Parity screening selected milk records from the first 1, 2, or 3 parities. Therefore, 4 evaluations (PTA₁) included only first-parity records available for daughters and contemporaries prior to the respective years designated. Four more evaluations (PTA_1,2) included the records from the first 2 parities for cows first calving prior to those same year cutoffs; likewise, the last 4 evaluations (PTA_1,2,3) included records from the first 3 parities. Stability of bull evaluations (standard deviations of differences as well as correlations between bull evaluations) across time was compared. Bulls born after 1984 with ≥500 daughters were of interest because of the high precision of evaluations and recent activity. Tailored PTA of those bulls had more uniformity across years in mean records per daughter than did official USDA PTA. Standard deviation of differences in PTA₁, PTA_1,2, and PTA_1,2,3 for milk between evaluation years 1996 and 1997 were 28, 28, and 27 kg compared with 63 kg for official evaluations; similarly, between 1996 and 1999, SD were 36, 32, and 32 kg compared with 80 kg. Results suggested that a modification to the current evaluation model to account for maturity rate should reduce fluctuations in individual bull PTA across time and may improve accuracy of evaluations.     

Genetic evaluation of calving ease for Brown Swiss and Jersey bulls from purebred and crossbred calvings

The objective of this study was to examine the feasibility of implementing routine national calving ease (CE) genetic evaluations of Brown Swiss (BS) and Jersey (JE) sires that include records of crossbred calvings. Records were available for 11,793 BS calvings, 3431 BS-sired crosses, 65,293 JE calvings, and 7090 JE-sired crosses. Evaluations were performed for each breed using only purebred calvings and using both purebred and crossbred calvings. In the latter evaluations, the sire-maternal grandsire model used for the routine evaluation of Holstein (HO) CE was modified to include a fixed breed composition effect to account for differences between purebred and crossbred calvings. Jersey cows had very little calving difficulty (0.5 to 0.7%) and JE bulls had a very small range of evaluations, suggesting that a routine JE evaluation would be of little value. Results from the BS evaluations suggest a routine evaluation would provide BS breeders with a useful tool for genetic improvement. Further examination of data showed that many BS calvings were in mixed herds with HO calvings. As a result, a joint evaluation for BS and HO bulls was developed. The BS data showed that there is similar genetic variability as found in the HO population, which suggests implementation of a routine evaluation including BS CE would be of value. It appears BS bulls may produce daughters with superior maternal calving ability compared with HO. Validation of the joint evaluation was performed by comparing results with the routine HO evaluation. Holstein solutions from the joint evaluation were comparable to results from the routine HO-only evaluation. Correlations among solutions and evaluations showed HO evaluations were not adversely affected by BS data and BS sires were reranked as compared with the BS-only evaluation.     

Comparisons of cows and herds in two progeny testing programs and two corresponding states

Data were USDA genetic evaluations of cows and DHI herd profiles from 4154 Holstein progeny-test herds from two artificial insemination organizations. 21st Century Genetics (Shawano, WI) and Genex (Ithaca, NY), and from 6361 additional herds from Minnesota and New York. We grouped herds into four categories: 21st Century Genetics herds, other Minnesota herds, Genex herds, and other New York herds. Herds were eliminated if they contributed fewer than 10 cows with genetic evaluations and birth dates from January 1989 to March 1995. Data included 83 and 74%, respectively, of first-crop daughters of 21st Century Genetics and Genex progeny-test bulls with genetic evaluations from January 1995 to February 1997. Herds were characterized by DHI profile and cow evaluation data. Daughters of progeny-test bulls with extreme production records (outside of 3 SD) relative to herd mean and variance did not appear in disproportionate numbers among the progeny of bulls likely culled or considered for further use. The two organizations appear to have selected larger, genetically superior, and better managed herds from within their respective regions for progeny-testing purposes. We were not able to predict whether a bull in the progeny-testing programs of these two organizations was going to exceed or fail to meet the pedigree prediction from characteristics of herds in which his daughters performed. Differences between parent average and daughter yield deviations for typical young sires appear to result from Mendelian segregation of genes.     

Overview of progeny-test programs of artificial-insemination organizations in the United States

Characteristics of progeny-test (PT) programs of artificial insemination (AI) organizations in the United States were examined for changes since 1960. Mean number of bulls that were progeny tested annually by major AI organizations during the mid 1990s was 11 for Ayrshires, 24 for Brown Swiss, 21 for Guernseys, 1261 for Holsteins, 112 for Jerseys, and 3 for Milking Shorthorns. Mean parent age at progeny-test (PT) bull birth decreased except for Milking Shorthorns; mean age of maternal grandsire at bull birth decreased for Holsteins and Jerseys but increased for other breeds. For Holsteins, mean ancestor ages at PT bull birth were 85 mo for sires, 47 mo for dams, and 136 mo for maternal grandsires during the mid 1990s. Percentage of PT bulls that resulted from embryo transfer increased to 78% for Brown Swiss and 80% for Holsteins by 1999. Inbreeding in PT bulls increased over time and ranged from 3.8% for Brown Swiss to 6.4% for Jerseys (5.6% for Holsteins) during the mid 1990s. Mean numbers of daughters and herds per PT bull generally declined except for Holsteins, which increased during the early 1990s to 61 daughters and 44 herds. Mean number of states in which PT daughters are located increased; for Holstein PT bulls during 1994, 22% of daughters were in California, 13% in Wisconsin, 12% in New York, and 10% in Pennsylvania and Minnesota. Percentage of first-lactation cows that were PT daughters increased and ranged from 6% for Milking Shorthorns to 22% for Ayrshires (14% for Holsteins) during 1998. Percentage of PT daughters that were registered declined and was 19% for Holsteins and around 80% for other breeds.     

Heritability of changes in genetic evaluations of dairy bulls from first to later records of daughters

Objectives of this study were to investigate changes in predicted transmitting abilities (PTA) of yields from evaluations based on first records to evaluations based on first and later records of daughters and determine whether these changes are heritable. Data were USDA sire evaluations of July 1989 through May 2000 on Holstein bulls in standard progeny testing programs. Changes in PTA for milk, fat, and protein from evaluations based on first records of daughters to evaluations on first and second were obtained on 2001 bulls. These were divided into two sets: subset 1 (n = 889) included bulls first evaluated before 1995 and subset 2 (n = 1112) included bulls first evaluated in 1995 and later. Changes in PTA from first-record evaluation to most recent evaluation (May 2000) were obtained on 2524 bulls first evaluated in 1995 or later. Mean changes in PTA for bulls first evaluated in 1995 and later were smaller than mean changes for bulls evaluated earlier but standard deviations were similar. Regressions of changes in PTA on changes in parent average showed that a change of 1.0 kg in parent average resulted in 1.1 to 1.2 kg change in PTA. Heritabilities estimated with animal model ranged from 0.14 to 0.23 for changes from first-record evaluation to evaluation on first and second, and 0.27 to 0.35 for changes from first-record evaluation to most recent evaluation. Heritabilities of this magnitude allow for identifying bulls that decrease in PTA.     

Differences among methods to validate genomic evaluations for dairy cattle

Two methods of testing predictions from genomic evaluations were investigated. Data used were from the August 2006 and April 2010 official USDA genetic evaluations of dairy cattle. The training data set consisted of both cows and bulls that were proven (had own or daughter information) as of August 2006 and included 8,022, 1,959, and 1,056 Holsteins, Jerseys, and Brown Swiss, respectively. The validation data set consisted of bulls that were unproven as of August 2006 and were proven by April 2010 with 2,653, 411, and 132 Holsteins, Jerseys, and Brown Swiss for the production traits. Method 1 used the training animal's predicted transmitting ability (PTA) from August of 2006. Method 2 used the training animal's April 2010 PTA to estimate single nucleotide polymorphism effects. Both methods were tested using several regressions with the same validation animals. In both cases, the validation animals were tested using the deregressed April 2010 PTA. All traits that had genomic evaluations from the official USDA April 2010 genetic evaluations were tested. Results included bias, differences from expected regressions (calculated using selection intensities), and the coefficients of determination. The genomic information increased the predictive ability for most of the traits in all of the breeds. The 2 methods of testing resulted in some differences that would affect interpretation of results. The coefficient of determination was higher for all traits using method 2. This was the expected result as the data were not independent because evaluations of the validation bulls contributed to their sires’ evaluations. The regression coefficients from method 2 were often higher than the regression coefficients from method 1. Many traits had regression coefficients that were higher than 2 standard deviations from the expected regressions when using method 2. This was partially due to the lack of independence of the training and validation data sets. Most traits did have some level of bias in the prediction equations, regardless of breed. The use of method 1 made it possible to evaluate the increased accuracy in proven first-crop bull evaluations by using genomic information. Proven first-crop bulls had an increase in accuracy from the addition of genomic information. It is advised to use method 1 for validation of genomic evaluations.     

Genetic analysis of an artificial insemination progeny test program

The success of the progeny test (PT) program from one Spanish artificial insemination (AI) organization was evaluated. The annual genetic trend for the organization was compared with PT programs from other countries. The relationships among parents' estimated breeding values (EBV) and PT results for sons were also studied. Estimated breeding values for type and production traits were obtained from international genetic evaluations from February 2004. The annual genetic gain of the Spanish PT program was similar to that of other international programs. The Spanish AI organization graduated 13% of its sampled bulls, and 52% of primiparous cows were daughters of Spanish bulls (32% from proven bulls and 20% from sampling bulls).Correlations between EBV for PT bulls and their pedigree indices (0.52 to 0.70) were slightly lower than correlations between EBV for PT bulls and their parent averages (0.63 to 0.73). Both young and mature cows contributed to genetic progress. Success of PT bulls (defined by number of second-crop daughters) depended mainly on their EBV for final score, protein yield, and the type-production index. Significant correlations of sire EBV were found for final score and type-production index with the number of second-crop daughters (0.22 and 0.17). Likewise, significant correlations of dam EBV for final score and type-production index with the number of second crop daughters were found (0.25 and 0.18). Final score and protein yield were the main factors in success of a PT bull. The type-production index for PT bulls was not important for success unless it was 2.5 standard deviations above average. The PT bulls with low EBV for type-production index were used as proven bulls when they had higher EBV either for protein or final score.     

Relationships of productive life evaluations with changes in evaluations for yields

The objective of this work was to investigate the relationships of productive life with changes in bull evaluations for yield traits. Two datasets were analyzed. In the first, predicted differences for change in milk yield from first to second lactation of daughters of artificial insemination (AI) Holstein bulls used widely in the southeastern United States were available from a previous study. These were correlated with predicted transmitting abilities (PTA) of productive life from May 2000 USDA sire evaluations. Based on bulls with at least 10 daughters (n = 560) the correlation of PTA productive life with predicted differences for the change in milk yield was 0.30. The correlation increased to 0.36 for bulls with at least 50 daughters (n = 319) and to 0.40 for bulls with at least 75 daughters (n = 284). The second analysis included data on 1831 AI sampled Holstein bulls evaluated by USDA between July 1989 and May 2000. Changes in PTA yields were calculated as PTA from evaluations based on first and second records of daughters minus those from first-record evaluations. Correlation analyses showed that PTA yields from first-record evaluation and changes in PTA yields were positively associated with productive life. Regression coefficients on changes in PTA yields were all positive indicating that increases in PTA for yield traits as daughters aged corresponded with longer productive life. Using changes in AI bull evaluations for yields could improve prediction of productive life for little cost.     

Assessment of the value of international genetic evaluations for yield in predicting domestic breeding values for foreign Holstein bulls

International genetic evaluations are a valuable source of information for decisions about the importation of (the semen of) foreign bulls. This study analyzed data from 6 countries (Australia, Canada, Italy, France, the Netherlands, and the United States) and compared international evaluations for production traits of foreign bulls (i.e., when no national daughter information was available) to their national breeding values in August 2009, which were based only on domestic daughters’ data. A total of 821 bulls with highly reliable estimated breeding values (EBV) for milk, fat, and protein yield were analyzed. No evidence of systematic over- or underestimation was found in most of the countries analyzed. Observed correlations between national and international evaluations were close to 0.9 and, for most countries, generally close to their expected values (calculated from national and international EBV reliabilities). In Italy, however, higher differences between observed and expected correlations and significant mean differences between EBV for more than one trait were observed in bulls progeny-tested in the United States and in other European countries (with differences up to 33.1% of the genetic standard deviation). These results were probably induced by a relatively recent change in the model for national evaluation. The findings in this study reflect a conservative estimate of the real value of international evaluations, as changes in methodologies in either the national or the international evaluations decreased the ability of past international evaluations to predict current national evaluations. Nevertheless, our results indicate that international evaluations based on foreign information for Holstein bulls were reasonably accurate predictors of the future national breeding values based only upon domestic daughters.     

Proven and young Holstein bulls compared for daughter yields, productive life, somatic cell score, and inbreeding

The objective of this study was to compare daughters of proven (progeny-tested) and young sampling bulls available for use at the same time for yield traits, productive life, somatic cell score, and inbreeding. Data were from USDA sire evaluations of July 1989 through July 1994. Proven bulls used between 1989 and 1994 were identified based on the change in number of daughters. Young bulls were identified based on age and date a bull first entered artificial insemination. Young bulls were classified into two categories: one included all young bulls available in one year and the other included the top 50% on parent average for milk. Daughter deviations for yields, productive life and somatic cell scores, and average inbreeding were obtained from May 2000 evaluation. Daughter deviation milk was not different between proven and top 50% young bulls but was lower for all young bulls. Young bulls (all and top 50%) exceeded proven bulls in daughter deviation fat and protein. Progeny of proven bulls had favorably higher productive life in most years but unfavorably higher somatic cell score than progeny of young bulls. Inbreeding was consistently higher for daughters of young bulls than for those of proven bulls. Results indicate that young bulls were competitive with proven bulls. Use of young bulls from among the top 50% should result in equal or higher genetic progress in yields compared to contemporaries by proven bulls.     

Evaluating sire selection practices using lifetime net income functions

Dairy farmers do not take full advantage of opportunities available for genetic improvement through use of artificial insemination, perhaps because economic advantages of good sire selection may not be fully recognized or understood. This study was undertaken to document differences between use of AI and non-AI bulls and to develop prediction equations to compare lifetime economic merit of future progeny from alternative sire selection policies. We describe the use of two methods of measuring lifetime economic merit, with and without adjustment for opportunity cost of a postponed replacement. Comparison of lifetime relative net income adjusted for opportunity cost on groups of cows sired by different kinds of bulls showed that daughters of proven AI bulls generated $148 and $120 more lifetime net income under fluid and manufactured milk market conditions than daughters of non-AI bulls. Daughters of proven AI bulls produced $60 more than daughters of AI young sires in progeny testing programs at the time of daughter conception. We developed prediction equations from combinations of genetic evaluations for production, productive life, SCS, and linear type traits on sires to predict lifetime relative net income of progeny produced from alternative sire selection strategies. Prediction equations explained 14 to 18% of variation in relative net income (not adjusted for opportunity cost), but herd and year of first freshening accounted for considerably more variation than did genetic evaluations on the sire of the cow. Finally, two independent data sets were used to develop and test predictions of lifetime relative net income adjusted for opportunity cost using genetic evaluations based on the eight traits included in the Merit indexes for the sire of each cow. Prediction equations from odd numbered herds were used to predict lifetime economic merit in even numbered herds and vice versa. Coefficients of determination ranged from 0.088 to 0.103 and averaged 0.004 higher than prediction equations with Net or Fluid Merit. Accuracy of predictions showed that Net and Fluid Merit were robust and useful indexes that accurately identified bulls whose daughters generated highest lifetime economic merit.     

Improving national fertility evaluations by accounting for the rapid rise of embryo transfer in US dairy cattle

Dairy producers have improved fertility of their herds by selecting bulls with higher conception rate evaluations. This research was motivated by the rapid increase in embryo transfer (ET) use to 11% of recent births and >1 million total births, with >5 times as many ET calves born in the United States in 2021 compared with just 5 yr earlier. Historical data used in genetic evaluations are stored in the National Cooperator Database. Recent records in the national pedigree database revealed that only 1% of ET calves have corresponding ET records in the breeding event database, 2% are incorrectly reported as artificial inseminations, and 97% have no associated breeding event. Embryo donation events are also rarely reported. Herd years reporting >10% of calves born by ET but less than half of the expected number of ET breeding events were removed to avoid potential biases. Heifer, cow, and sire conception rate evaluations were recalculated with this new data set according to the methods used for the official national evaluations. The edits removed about 1% of fertility records in the most recent 4 yr. Subsequent analysis showed that censoring herd years with inconsistent ET reporting had little effect on most bulls except for the highest ranking, younger bulls popular for ET use, and with largest effects on genomic selection. Improved ET reporting will be critical for providing accurate fertility evaluations, especially as the popularity of these advanced reproductive technologies continues to rise.     

Comparison of genetic evaluations from animal model and modified contemporary comparison

Comparisons were made between characteristics of Modified Contemporary Comparison and animal model evaluations with data available for January 1989 USDA-DHIA genetic evaluations. The animal model system's requirement that cows have a valid first lactation record resulted in a decrease in cows and daughters included. New flexible comparison groups were slightly larger for small herds and much smaller for large herds, which resulted in overall smaller and more uniform-sized comparison groups. Determining the optimal method of defining management groups was not undertaken. Correlations between bull evaluations from the two procedures ranged from .92 to .95 across breeds. Increases in reliability over repeatability were substantial for bulls with limited daughter information and small for widely used bulls. Correlations between evaluations for cows born in 1985 were .92 to .96, whereas those for cows born in 1980 (old enough to have daughters affecting animal model evaluations) were lower (.90 to .93), as expected. Reliabilities for cows were .02 to .05 higher than repeatabilities. Cows with more daughters increased more in evaluation and accuracy between the two procedures and were genetically superior. Bulls and cows with more prior information, cows with higher past evaluations, and Holstein bulls with higher past evaluations tended to have larger increases in PTA. Genetic trend estimates were different for the animal model, which resulted in changes in evaluations of various magnitudes depending on breed, sex, and birth year of animal.     

Genetics of reproduction in primiparous Holsteins

Effects of genetics and relationships between yield and days from parturition to first service, first service conception rate, number of services, and a reproductive performance code based on several reproductive components were investigated in primiparous Holsteins. Recorded breedings and DHI production records were from 3393 daughters of 174 bulls in six experimental herds. Subsets included progeny of 78 sires, with greater than or equal to 5 daughters calving in April through July (n = 817) and August through March (n = 1162). Daughter-dam regressions (n = 2593 pairs) and paternal half-sibs were used to estimate heritabilities of fertility traits and associations between yield and reproduction. Results showed increased FCM was associated with lowered fertility. For paternal half-sibs, the greatest antagonism was between conception rates and FCM (rG = -.65 +/- .10). Daughter-dam regressions estimated a favorable genetic correlation of .43 +/- .32 between conception rates and yield. Heritabilities were highest for April through July calvings and ranged from .08 +/- .10 for first service conception to .24 +/- .12 for reproductive code. Correlations between sire least squares constants from warmer and cooler calving seasons were lower than heritabilities of traits would suggest.     

Short communication: Genetic evaluation of milking speed for Brown Swiss dairy cattle in the United States

Genetic parameters and relative breeding values were estimated for milking speed of US Brown Swiss dairy cattle. Owner-recorded milking-speed scores on a scale of 1 (slow) to 8 (fast) were collected by the Brown Swiss Association as part of its linear type appraisal program starting in 2004. Data were 7,366 records for 6,666 cows in 393 herds. The pedigree file included information for 21,458 animals born in 1985 or later. Six unknown-parent groups that each included 4 birth years were defined. The model included fixed effects for herd appraisal date and parity-lactation stage and random effects for permanent environment, animal, and error. Within parity (1, 2, and ≥3), 6 groups were defined: unknown calving date, four 90-d lactation stages, and lactations with >400 d in milk. Heritability of 0.22 and repeatability of 0.42 were estimated by average-information REML; residual variance was 1.13. Little trend in estimated breeding value was found for cows born from 1999 through 2002. Although solutions increased with lactation stage for first-parity cows by 0.37, no clear trend was found for later parities. Genetic evaluations for milking speed were expressed as relative breeding values with a mean of 100 and a standard deviation of 5. The 121 bulls with ≥10 daughters had milking speed evaluations that ranged from 83 to 112 and had correlations of 0.56 with productive life evaluations and −0.40 with somatic cell score evaluations. The association of faster milking speed with lower somatic cell score was not expected. The moderate heritability found for milking speed indicates that the evaluations (first released in May 2006) should be useful in detecting bulls with slow-milking daughters.     

Birth traits of pure Holstein calves versus Montbeliarde-sired crossbred calves

Pure Holstein calves and Montbeliarde-sired crossbred calves from multiparous Holstein dams were compared for gestation length, calf weight at birth, calving difficulty, and stillbirth in 2 research herds of the University of Minnesota. The Montbeliarde-sired calves from multiparous Holstein dams had significantly longer gestation lengths (283.2 d) than Holstein-sired calves from Holstein dams (278.4 d), and Montbeliarde-sired calves from multiparous Holstein dams had significantly greater calf weight at birth (48.3 kg) compared with Holstein-sired calves from Holstein dams (43.3 kg). However, calves sired by Montbeliarde bulls were not significantly different from calves sired by Holstein bulls for calving difficulty and stillbirth. In addition, Jersey × Holstein crossbred cows mated to Montbeliarde artificial insemination (AI) bulls were compared with pure Holstein cows mated to Holstein AI bulls for gestation length, calf weight at birth, calving difficulty, and stillbirth at their first 3 calvings. Gestation length was significantly longer for Jersey × Holstein cows bred to Montbeliarde bulls than for pure Holstein cows bred to Holstein bulls at first calving (280.3 versus 277.7 d) and second and third calving (282.2 versus 278.6 d); however, Jeresy × Holstein cows bred to Montbeliarde AI bulls were not significantly different from pure Holstein cows bred to Holstein AI bulls for calf weight at birth, calving difficulty, and stillbirth at the first 3 calvings.