Artificial Insemination Organizations Research Articles

Genomic selection in United States dairy cattle.

The genomic selection program for dairy cattle in the United States has doubled the rate of genetic gain. Since 2010, the average annual increase in net merit has been $85 compared to $40 during the previous 5 years. The number of genotypes has been rapidly increasing both domestically and internationally and reached over 6.5 million in 2022 with 1,134,593 submitted in 2021. Evaluations are calculated for over 50 traits. Feed efficiency (residual feed intake), heifer and cow livability, age at first calving, six health traits, and gestation length have been added in recent years to represent the economic value of selection candidates more accurately; work is underway to develop evaluations for hoof health. Evaluations of animals with newly submitted genotypes are calculated weekly. In April 2019, evaluations were extended to crossbreds; to support that effort, evaluations are initially calculated on an all-breed base and then blended by an estimated breed composition. For animals that are less than 90% of one breed, the evaluation is calculated by weighting contributions of each of the five major dairy breeds evaluated (Ayrshire, Brown Swiss, Guernsey, Holstein, and Jersey) by the breed proportion. Nearly 200,000 animals received blended evaluations in July 2022. Pedigree is augmented by using haplotype matching to discover maternal grandsires and great-grandsires. Haplotype analysis is also used to discover undesirable recessive conditions. In many cases, the causative variant has been identified, and results from a gene test or inclusion on a genotyping chip improves the accuracy of those determinations for the current 27 conditions reported. Recently discovered recessive conditions include neuropathy with splayed forelimbs in Jerseys, early embryonic death in Holsteins, and curly calves in Ayrshires. Techniques have been developed to support rapid searches for parent-progeny relationships and identical genotypes among all likely genotypes, which substantially reduces processing time. Work continues on using sequence data to discover additional informative single nucleotide polymorphisms and to incorporate those previously discovered. Adoption of genotyping by sequencing is expected to improve flexibility of marker selection. The success of the Council on Dairy Cattle Breeding in conducting the genetic evaluation program is the result of close cooperation with industry and research groups, including the United States Department of Agriculture, breed associations, genotyping laboratories, and artificial-insemination organizations.

113 Genetics Industry Infrastructure: How Are Artificial Insemination Organizations Adapting to Changes in the Beef Industry?

Abstract Cattle artificial insemination (AI) organizations are adapting quickly to changes within the beef industry domestically and abroad. Specifically, the increasing utilization of beef bulls, predominately Angus, in dairy herds to create terminal crossbred calves for beef underlies the majority of the changes and challenges. The procurement, management, and collection of beef sires on a commercial scale has become commonplace for AI organizations, and the subsequent optimization of beef sire housing, nutritional requirements, behavior surrounding semen collection, semen production ability, semen quality, and fertility is being examined. At one large AI organization, Angus sires are proving capable of producing as much semen as their dairy counterparts while being collected year-round to meet market demand. However, the percentage of collections that qualify for sale is ≤80% in beef bulls compared to >90% in Holstein bulls based on acceptable semen quality as determined by post-thaw computer-assisted motility analyses, flow cytometric viability assays, and visual sperm morphological assessment (Select Sires, Inc., unpublished). Large numbers of inseminations using beef sires, combined with reliable data recording on dairies, is allowing for precision management tools and sire fertility estimates to be generated. For example, the Council on Dairy Cattle Breeding (CDCB) recently applied the Sire Conception Rate (SCR) evaluation’s statistical model to Angus bulls used to inseminate Holstein cows and reported similar conception rates to Holstein sires used to inseminate Holstein cows (33.8% versus 34.3%, respectively). AI organizations have also begun to implement research, create products, and establish new supply chains to proactively account for dairy farms supplying crossbred or purebred (via embryo transfer) beef animals to calf ranches, feed yards, and packer networks. Examples include purebred commercial beef embryo sales, research on rearing crossbred beef calves, generating novel value-based (grid pricing) markets for crossbred calves, and facilitating traceability programs for packers.

Optimizing semen production for artificial insemination in swine

Efficient production of high quality semen is of major importance to artificial insemination (Al) organizations. The semen produced should be free of contagious organisms, be of high quality, have good storage properties, fertilizing capacity and be of high genetic value. The best approach to prevent the spreading of microorganisms via semen in the process of Al is to collect semen from boars free from specific diseases, for example pseudorabies virus or leptospirosis. Antibiotics are added to the semen to suppress proliferation of microorganisms or even reduce their number. Sperm production is influenced by many factors such as season, collection frequency, breed and age. The average number of sperm cells produced per boar per week can vary more than 30% within one Al station, depending on the breed. Boar selection and boar management markedly influence the efficiency of sperm production. Sperm quality should be evaluated by fertility results obtained at breeding farms related to both farrowing rate and litter size to ensure a good quality monitoring system. A quality control system should be established to provide maximum reliability to customers.

Mating programs including genomic relationships and dominance effects

Computerized mating programs using genomic information are needed by breed associations, artificial-insemination organizations, and on-farm software providers, but such software is already challenged by the size of the relationship matrix. As of October 2012, over 230,000 Holsteins obtained genomic predictions in North America. Efficient methods of storing, computing, and transferring genomic relationships from a central database to customers via a web query were developed for approximately 165,000 genotyped cows and the subset of 1,518 bulls whose semen was available for purchase at that time. This study, utilizing 3 breeds, investigated differences in sire selection, methods of assigning mates, the use of genomic or pedigree relationships, and the effect of including dominance effects in a mating program. For both Jerseys and Holsteins, selection and mating programs were tested using the top 50 marketed bulls for genomic and traditional lifetime net merit as well as 50 randomly selected bulls. The 500 youngest genotyped cows in the largest herd in each breed were assigned mates of the same breed with limits of 10 cows per bull and 1 bull per cow (only 79 cows and 8 bulls for Brown Swiss). A dominance variance of 4.1 and 3.7% was estimated for Holsteins and Jerseys using 45,187 markers and management group deviation for milk yield. Sire selection was identified as the most important component of improving expected progeny value, followed by managing inbreeding and then inclusion of dominance. The respective percentage gains for milk yield in this study were 64, 27, and 9, for Holsteins and 73, 20, and 7 for Jerseys. The linear programming method of assigning a mate outperformed sequential selection by reducing genomic or pedigree inbreeding by 0.86 to 1.06 and 0.93 to 1.41, respectively. Use of genomic over pedigree relationship information provided a larger decrease in expected progeny inbreeding and thus greater expected progeny value. Based on lifetime net merit, the economic value of using genomic relationships was >$3 million per year for Holsteins when applied to all genotyped females, assuming that each will provide 1 replacement. Previous mating programs required transferring only a pedigree file to customers, but better service is possible by incorporating genomic relationships, more precise mate allocation, and dominance effects. Economic benefits will continue to grow as more females are genotyped.

The genomic evaluation system in the United States: Past, present, future

Implementation of genomic evaluation has caused profound changes in dairy cattle breeding. All young bulls bought by major artificial insemination organizations now are selected based on such evaluation. Evaluation reliability can reach approximately 75% for yield traits, which is adequate for marketing semen of 2-yr-old bulls. Shortened generation interval from using genomic evaluations is the most important factor in increasing the rate of genetic improvement. Genomic evaluations are based on 42,503 single nucleotide polymorphisms (SNP) genotyped with technology that became available in 2007. The first unofficial USDA genomic evaluations were released in 2008 and became official for Holsteins, Jerseys, and Brown Swiss in 2009. Evaluation accuracy has increased steadily from including additional bulls with genotypes and traditional evaluations (predictor animals). Some of that increase occurs automatically as young genotyped bulls receive a progeny test evaluation at 5 yr of age. Cow contribution to evaluation accuracy is increased by decreasing mean and variance of their evaluations so that they are similar to bull evaluations. Integration of US and Canadian genotype databases was critical to achieving acceptable initial accuracy and continues to benefit both countries. Genotype exchange with other countries added predictor bulls for Brown Swiss. In 2010, a low-density chip with 2,900 SNP and a high-density chip with 777,962 SNP were released. The low-density chip has increased greatly the number of animals genotyped and is expected to replace microsatellites in parentage verification. The high-density chip can increase evaluation accuracy by better tracking of loci responsible for genetic differences. To integrate information from chips of various densities, a method to impute missing genotypes was developed based on splitting each genotype into its maternal and paternal haplotypes and tracing their inheritance through the pedigree. The same method is used to impute genotypes of nongenotyped dams based on genotyped progeny and mates. Reliability of resulting evaluations is discounted to reflect errors inherent in the process. Further increases in evaluation accuracy are expected because of added predictor animals and more SNP. The large population of existing genotypes can be used to evaluate new traits; however, phenotypic observations must be obtained for enough animals to allow estimation of SNP effects with sufficient accuracy for application to the general population.

Temporal trends in bull semen quality: A comparative model for human health?

Introduction A decline in human semen quality over the past 30–60 years has been reported in numerous epidemiological studies from the United States and Europe. We evaluated temporal trends in semen quality parameters in dairy bulls. The long-term management of dairy bulls for artificial insemination presented a unique opportunity to evaluate temporal trends in semen quality and explore this relationship as a potential animal model for reproductive abnormalities in humans. Materials and methods Bull semen analysis data from 1965 through 1995 were collected from a large artificial insemination organization. Semen analyses from 12- to 18-month-old Holstein dairy bulls were included in the study and consisted of daily sperm concentration, daily ejaculate volume, total daily sperm output, percentage of sperm with normal morphology, and percentage of sperm with normal post-thaw motility. Multiple regression analysis, logistic regression, and general linear modeling were used to determine temporal trends over the 30-year period. Results and discussion Semen quality appears to have declined from 1970 to 1980 or 1985 as manifested by declines in daily ejaculate volume, daily sperm concentration, and total daily sperm output. In contrast, sperm morphology and motility improved over the same period. In approximately 1980 or 1985, depending on the parameter, ejaculate volume, sperm concentration, total sperm, and motility improved. However, normal morphology began to deteriorate during this same period. Methodological inconsistencies over time introduce uncertainty in analyses of temporal trends in semen quality in this and previous human studies. However, changes in technology do not appear to be solely responsible for the temporal trends observed. The source of the decline in semen quality in the bulls studied is unknown. If the decline in semen quality were due to exposure to endocrine disrupting chemicals, then a continued decline or a leveling-off would be expected. Instead, a rise in semen quality was observed during the latter portion of the observation period.

Exploring the Impact of Sexed Semen on the Structure of the Dairy Industry

Widespread commercial application of sexed semen is expected within the next decade because of continued improvements in fertility of sexed semen and sorting capacity. The objective of this study was to explore the potential impact of widespread application of sexed semen on the structure of the dairy industry in the United States. Historically, female offspring from all heifers and cows were needed to produce enough dairy replacement heifers to replace culled cows. The use of sexed semen allows for a decoupling of breeding decisions necessary to obtain an adequate supply of dairy replacement heifers from those needed to achieve pregnancies needed to start new lactations. Application of sexed semen allows dairy producers to select among their herds’ potential dams and produce dairy replacement heifers from only the genetically superior animals. The rate of genetic progress is expected to increase, but not more than 15% of the rate of gain accomplished through sire selection achieved through conventional (nonsexed) artificial insemination breeding. The supply of dairy replacement heifers is expected to grow to meet and temporarily exceed current demand, resulting in reduced prices for dairy replacement heifers. Consequently, herd turnover rates are expected to increase slightly, and herd expansions may accelerate. The rate of consolidation of dairy farms is expected to increase. Widespread application of sexed semen may temporarily increase the supply of milk, which would result in lower milk prices. The cost of milk production will be reduced as well. Many breeding options exist for the genetically poorer cows in the herd. The optimal breeding mix depends on the value of the various kinds of calves that could be produced. More crossbred calves for beef production may be produced; however, a market for these crossbred calves is not well established. Increased specialization is expected with more dairy producers deciding not to raise their own heifers but to purchase replacements. Other dairy farms might specialize in producing genetically superior dairy replacement heifers for sale. Depending on the value of calves not raised for replacements, artificial insemination organizations might market beef conventional semen or beef male sexed semen to dairy farms. The use of sexed semen should lower the cost of progeny-testing programs and embryo transfer and enhance the value of genetic markers. Eventually, the economic benefits from the use of sexed semen will be passed on to consumers.

Application of Controlling Instruments for Improvements in Cow Sire Selection

National estimated breeding values of bulls from 1998 through 2006 from 12 different German artificial insemination (AI) organizations were used to determine the differences in expected and realized selection intensities for cow sire selection, considering the total merit index as well as subindexes for production, conformation, somatic cell count, fertility, and functional herd life. The expected selection intensity was derived from a Gaussian distribution and from the replacement rate describing the percentage of bulls graduated as cow sires from the total amount of progeny-tested young bulls within the AI organization and by birth year. Realized selection intensities for all indexes were derived from the selection differential of cow sires, defined as the deviation of the average index of selected cow sires from the average index of the total number of progeny-tested young bulls. A low replacement rate of cow sires was associated with relatively high realized selection intensities for the total merit, production, and conformation indexes, but was not related to the somatic cell count, fertility, and functional herd life indexes. The controlling value, defined as the ratio of realized to expected selection intensities, indicates the effectiveness of cow sire selection for different traits. Low controlling values (i.e., low realized selection intensities in combination with moderate or high expected selection intensities) suggest improvements in the step of cow sire selection, especially when discussing the total merit index. Analysis of variance revealed significant differences in expected selection intensities, realized selection intensities, and controlling values for the total merit, production, and conformation indexes between AI organizations and birth years of bulls. Artificial insemination organizations applying well-defined breeding policies (e.g., high controlling values for the total merit index) were successful in the national competition when evaluated according to the national top lists for the respective indexes, regardless of the active population size. The suggested method also allows for comparison of the importance of different indexes in selection decisions. Furthermore, controlling values can monitor additional potential in the improvement of cow sire selection with respect to improvement of the genetic level in the whole population. The development of appropriate selection tools or controlling instruments is of increasing concern for monitoring selection policies in the short term as well as for establishing sustainable breeding policies.

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.

Prediction of Most Recent Evaluations of Holstein Bulls from First Available Pedigree Information

The objectives of this study were to predict most recent evaluations of young bulls entering artificial insemination (AI) sampling programs from pedigree information available at time of sampling and investigate whether prediction equations differ among AI organizations. Data were pedigree information and most recent USDA evaluations on bulls entering AI sampling programs from 1989 through 1994. Pedigree information included earliest available parent average, predicted transmitting abilities (PTA) of sire, dam, and maternal grand sire. Most recent evaluations were from May 2000 evaluations and included PTA and daughter yield deviations for milk, fat, and protein. Regression coefficients on PTA of sire and PTA of dam were less than the expected coefficient of 0.50. Accuracy of prediction as determined by R-square values was less than 12%. Inclusion of PTA of maternal grand sire after PTA of sire and dam increased the accuracy of prediction by less than 1%, but regression coefficients on PTA of maternal grand sire differed from 0. Regressions on parent average were not different among AI organizations for prediction of PTA and daughter yield deviations. Partial regression coefficients on PTA of sire differed among AI organizations for prediction of fat and protein but did not differ for milk. Coefficients on PTA of dam did not differ among organizations. These results indicate that AI organizations put different emphasis on PTA of sire in selection of sons for fat and protein.

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.

Stability and Bias of Yield Evaluations for Holstein Bulls in Artificial Insemination Service

Holstein bull predicted transmitting abilities (PTA) for milk, fat, and protein yields were compared for January 1995 and May 2000, the beginning and end of the 1995 genetic base definition. Overall, PTA for the 14,012 artificial insemination (AI) bulls born in 1980 or later were stable for mean but varied slightly more than expected based on increase in data. As expected, changes were larger for bulls with lower initial reliability (accuracy) and greater increases in reliability over the 5.3 yr. For the 540 bulls in active AI service during 1995, mean PTA changes were near 0 (–8kg for milk, –1.3kg for fat, and –0.5kg for protein). Bulls in the top decile for PTA milk, fat, and protein declined 47, 2.2, and 2.2kg, respectively, but that bias was not evident for bulls that had been progeny tested by major AI organizations (sampling code S). The standard deviation for change in PTA milk for top decile bulls was 191kg; expected standard deviation was 140kg. Consideration of only bulls with a sampling code of S removed the excess variation, which indicates that bulls from other sampling programs are the source of bias and lack of stability. Bulls with a sampling code other than S appeared to have an initial PTA that was biased, largely because of an inflated estimate of daughter performance. The hypothesis that inflated means of parent PTA produce inflated early PTA of bulls was not corroborated. Stability of the genetic base and unbiasedness of PTA was demonstrated for bulls with a sampling code of S, but concern continues for bulls with other sampling codes. Because much of the bias in PTA for those bulls is expected to be the result of preferential management of early daughters, improvement of the evaluation system to remove that bias will be difficult.

Linkage disequilibrium in two‐stage marker‐assisted selection

Linkage disequilibrium in two‐stage marker‐assisted selection

Merit of Outliers for Milk Yield as Indicators of Accuracy of Genetic Evaluations of Sires

To determine whether the accuracy of the genetic evaluations of sires can be assessed by the presence of extreme daughter records, we studied herd-years with records from first-crop daughters of 217 Holstein bulls that were not sampled by artificial insemination (AI) organizations but that later entered AI. The presence of outliers for standardized milk yield was determined within herd-year. Outliers were defined as records exceeding 1.5 interquartile ranges below the 25th percentile or above the 75th percentile. Herd-years were separated into two groups based on whether or not an outlier daughter record was present for an AI bull that had initially been sampled through non-AI. Herd-years without daughter outliers from those bulls were divided into herd-years with 1) no daughter outliers from any bull, 2) only negative daughter outliers from other bulls, 3) only positive daughter outliers from other bulls, or 4) negative and positive daughter outliers from other bulls. Herd-years with daughter outliers from AI bulls initially sampled through non-AI were divided into herd-years with 1) only negative daughter outliers, 2) only positive daughter outliers, 3) positive daughter outliers from those bulls and negative daughter outliers from other bulls, or 4) both negative and positive daughter outliers. The relationship between the frequency of outlier classes and a change in the Modified Contemporary Comparison genetic evaluations (the difference between the last available second-crop evaluation and the next to the last first-crop evaluation) was examined with logistic regression. For AI bulls that were initially sampled through non-AI and having evaluations that decreased ≥386kg, 9% of herd-years had positive first-crop daughter outliers and negative daughter outliers from other bulls; 38% had no outliers. For bulls with evaluations that increased ≥194kg, comparable percentages were 2 and 53%.

Usability for Genetic Evaluations of Records from Herds Participating in Progeny Test Programs of Artificial Insemination Organizations

Thirteen AI organizations provided identification of herds that participated in their progeny test programs in 1989 and 1990; 15% of those herds participated in programs of more than one AI organization, but only 2.6% participated in programs of more than two AI organizations. Of the 19,589 participating herds, 82 and 76% were enrolled in DHI test plans that were considered to be usable for genetic evaluations during 1991 and 1992. For herds that had participated in AI progeny test programs, mean percentages of usable records were 77% in 1991 and 78% in 1992; the mean percentages of usable records for nonparticipating herds were 62% in 1991 and 60% in 1992. Participating herds had larger mean herd sizes, higher means and standard deviations of milk yields, younger cows, and a lower percentage of registered cows than did nonparticipating herds. Analysis of variance was used to explain the variation in the percentage of records that were usable for genetic evaluations. Herds that participated in AI progeny test programs or that had smaller herd sizes, higher mean milk yields, younger cows, or larger percentages of registered cows had higher percentages of records that were usable for genetic evaluations. Improved usability of records for genetic evaluations would increase the efficiency of AI progeny testing, and consideration of herd characteristics associated with higher percentages of usable records should aid AI organizations in evaluating prospective herds for progeny test programs.

Evaluation of Bulls for Nonreturn Rates Within Artificial Insemination Organizations

Programs have been written for use on microcomputers to utilize breeding receipt data collected by AI organizations to evaluate dairy bulls for nonreturn rates. The statistical model of analysis allows the user to have up to four fixed factors, as well as herd or herd-year effects, technician effects, and service sire effects. As an example, 137,874 AI in 1991 from one organization were analyzed. Data included information from 3609 herds, 80 technicians, and 464 sires. Although AI organizations traditionally compute 60- to 90-d nonreturn rates, these programs have caused organizations to consider using shorter period nonreturn rates in order to evaluate bulls sooner. Evidence from other work indicated that the evaluations of bulls from this analysis were more highly correlated with physiological characteristics of ejaculates than simple nonreturn rates.

Prediction of response with overlapping generations accounting for multistage selection

A generalization of Hill's equations predicting response to selection is developed that accounts for multiple stage selection in either or both sexes. The method accounts for the flow of genes for animals selected at later stages. This allows for the use of genetic gains from later stages, which explains the reduction in variance due to previous selection. Genetic gains from different selection differentials in each reproductive pathway are incorporated into the equations. The asymptotic response to a single cycle of selection is shown to agree with classical selection theory.The method is applied to a dairy progeny testing scheme representative of an artificial insemination organization in the USA. Two models were compared: (1) the first model accounted for two-stage selection of males, the first stage being based on pedigree information and the second stage on both pedigree and progeny test information; and (2) the second model assumed single-stage male selection. Selection was based on milk volume, milk fat, and milk protein yields. The predicted asymptotic rates for a single cycle of selection were overestimated by 6% and the cumulative response to continuous selection over 20 years was overestimated by 8% by assuming singlestage male selection.

A new antibiotic combination for frozen bovine semen, 3. Evaluation of fertility

Field fertility (nonreturn rate) studies were performed independently by three artificial insemination organizations to evaluate bovine semen processed for freezing using the antibiotics gentamicin, tylosin and Linco-Spectin at concentrations of 500 ug, 100 ug, and 300/600 ug, respectively, per milliliter of neat semen and per milliliter of nonglycerol portion of the extender. The antibiotic combination including penicillin, dihydrostreptomycin, polymyxin B sulfate, with/without Linco-Spectin (500 units/ml, 2000 ug/ml, 1000 units/ml and 300/600 ug/ml, respectively) was used as the control treatment. Results indicated no significant effect on seminal quality as measured by field fertility under the conditions of these experiments using heated whole milk or egg yolk-sodium citrate seminal extenders. Use of the new antibiotic combination has been adopted by Certified Semen Services.

Incidence and Inheritance of Deficiency for Uridine Monophosphate Synthase in Holstein Bulls

A partial deficiency of uridine monophosphate synthase has been discovered among Holstein dairy cattle wherein affected animals have half the normal activity of this enzyme and are heterozygous for a condition presumed to be lethal in the homozygous recessive state. A random sample of 287 dairy bulls, active in artificial insemination organizations, were assayed for their activity of uridine monophosphate synthase. Four bulls displayed reduced enzyme activity (heterozygotes) corresponding to a 1.4% incidence and were closely related to a common ancestor, Bull-X. Testing a total of 75 male descendants of Bull-X has uncovered 22 heterozygotes. Heterozygotes include 5 sons, 15 grandsons, 1 a double grandson, and 2 great grandsons of Bull-X. Reproductive failure from this enzyme deficiency has been minimal because matings between close relatives have been infrequent. If the incidence of heterozygotes active in artificial insemination increases, avoidance of matings between close relatives will become an inadequate safety measure to maintain reproductive fitness. Random mating of male heterozygotes to a female population with 2% incidence of heterozygotes may imply an additional .5% embryonic loss relative to matings involving bulls that are noramal for uridine monophosphate synthase.

Inheritance and Relationships of Linear Type Traits for Age Groups of Holsteins

Routine classifications from the linear type trait program of the Holstein Association were analyzed separately for age groups. Inheritance of linear type traits and their genetic and phenotypic relationships were evaluated. Estimates of genetic and phenotypic parameters were compared to other studies with experimental classifications from the Holstein Association and with data from artificial insemination organizations across age groups. Evaluation of sires for type traits across age groups may not properly rank sires if ages of daughters differ for sires. Future genetic evaluations of type by the Holstein Association will consider only classifications of cows closest to 30 mo, so heritabilities for linear type traits for only 2 yr olds from this study may have application. Some linear type traits are very similar genetically. Stature has substantial genetic association with final score as subjectively assigned by classifiers.