Service Bulls Research Articles

Restricted maximum likelihood (REML) estimation of genetic parameters for type traits in Normande cattle breed

Data on type traits (29 variables) from progeny of 437 Normande sampling bulls (16 356 daughters), connected through the progeny of 37 service bulls (14 170 daughters) were analysed in order to estimate genetic parameters (i.e. heritabilities and genetic correlations). In addition to the usual Henderson's Method 3, several methods for calculating REML estimates were used: Fisher's method of scoring, Newton-Raphson, EM (expectation-maximization) and accelerated EM. In terms of computational requirements, accelerated EM seemed to be the best for implementing REML. Differences between Henderson 3 and REML estimates and their sampling errors were very small. Possible reasons for this are discussed. Values of genetic parameters for type in the Normande breed were similar to their counterparts in Friesians or Holsteins. Furthermore, there was no need to use such a large number of variables for selection purposes. New synthetic variables could be constructed from a principal component analysis applied to the matrix of genetic correlation coefficients, thus allowing a substantial reduction of the useful variables and an improvement of their heritability values. The underlying idea was to define independent selection objectives on the standardized genetic scale.

Genetic Parameters for Fertility of Dairy Bulls

Genetic parameters for male fertility and fertility ratings of AI bulls were obtained by analyzing 298,013 service records of cows with successive calving records. Cows were mated to 746 service bulls, which were progeny of 126 sires. The model for variance component estimation accounted for fixed effects of herd-year-seasons, sire of the service bull, age of mates, and random effects of service bull and residual error. Estimates of variances of service bulls and residual error components for bull fertility indicated almost 10% of the phenotypic variation for fertility is among AI bulls. Best linear unbiased prediction of fertility ratings of individual bulls with inclusion of sire and maternal grandsire relationships on these data permitted the evaluation of 886 AI bulls for bull fertility. Heritability for bull fertility computed as twice the regression of son on sire was .158. Differences in fertility ratings of AI bulls ranged from −.29 to .19. Prediction of fertility of young AI bulls and more accurate rating of proven bulls might be useful to the industry.

Individual Variation for In Vitro Fertilization Success in Dairy Bulls

Individual semen samples from 29 bulls in routine artificial breeding service were tested for their capability to achieve in vitro fertilization. Ejaculated semen was diluted, .1ml of semen in 2ml of a modified Tyrode's medium with an osmolality of 340 mOsmol/kg, washed thrice, incubated 3h at 37°C before being used for in vitro fertilization, or incubated 4h and 8h before assessment of motility, capacitation, and acrosome integrity. The degree of variability in percentage of oocytes fertilized was assessed along with several factors that might contribute to this variation. Variation among bulls was not significantly different. Variation from one replicate to another was high. Variation was found in motility, capacitation, and frequency of acrosome reaction, but these variables were not significantly correlated to fertilization rate in vitro.

Reproductive Practices and Results in Dairies Using Owner or Professional Inseminators

In study 1, information on breeding practices of owner-inseminators in 234 herds of Holstein cattle was obtained by mail survey. Improved timing of insemination during estrus and convenience were reasons dairy farmers gave for performing insemination themselves. Many also used natural service bulls or professional inseminators to breed some cows. Cows in less than half of the herds were observed specifically for estrus at scheduled intervals. Cows were frequently inseminated more than once per estrus; 65% of the inseminations were within 2h of milking. Mean services per conception for cows in 135 herds responding to a second questionnaire were 1.7 and mean calving interval was 12.8 mo. Study 2 involved only herds and associated records in Dairy Herd Improvement. Herds using only professional inseminators were randomly selected to match similar owner-serviced responding and nonresponding tested herds in Study 1. Reproductive efficiency varied greatly among herds with a slight decrease as the size of the herd increased. The 1.70 services per conception achieved by professional technicians was only slightly better than 1.74 services per conception for direct service personnel. Dairy farmers in large herds who did not respond to a special questionnaire handled more cows per worker, had more services per conception, and had a slightly longer calving interval.

Individual Variation in Immunosuppressive Activity of Bovine Seminal Plasma on Concanavalin A-Stimulated Bovine T Lymphocytes In Vitro

Individual dialyzed seminal plasma samples from 21 bulls in routine artificial breeding service were tested for their immunosuppressive activity on in vitro induced blastogenesis of bovine lymphocytes from 3 nonpregnant cows. Concanavalin A was used to induce blastogenesis and thymidine uptake was monitored.Dialyzed seminal plasma from 15 of 21 bulls inhibited deoxyribonucleic acid synthesis response to concanavalin with cow A lymphocytes, and 21 of 21 were immunosuppressive to lymphocytes from cows B and C. Degree of immunosuppression varied according to bull and cow, ranging from 0 to 100%. The lower the percentage response of the lymphocytes to concanavalin stimulation, the less their inhibition by dialyzed seminal plasma. The degree of immunosuppression produced by a bull's dialyzed seminal plasma was not highly related either to amount of protein in the seminal plasma or to the bull's 60 to 90-d nonreturn rate.

Changes of Evaluation for Natural-Service Sampled Bulls Brought into Artificial Insemination

United States Department of Agriculture Sire Summary files were used to select bulls with a published Modified Contemporary Comparison sire evaluation prior to entry into artificial insemination. Canadian bulls were not included. Of the Brown Swiss, Guernsey, Holstein, and Jersey bulls that entered artificial insemination since 1974, 28 Brown Swiss, 19 Guernseys, 298 Holsteins, and 45 Jerseys (4 to 12%) had natural service evaluations. Of these bulls, 10 Guernseys, 154 Holsteins, and 28 Jerseys had an increase of Repeatability of 30% or more after entering artificial insemination. Evaluations for bulls just prior to their entering artificial insemination were compared with their most recent evaluations through July 1983. Average Repeatabilities for evaluations of bulls just prior to their entering artificial insemination were 32% for Guernseys, 32% for Holsteins, and 31% for Jerseys and 88, 90, and 87% for their most recent evaluations. Average Predicted Differences prior to entering artificial insemination were 305kg for Guernseys, 394kg for Holsteins, and 452kg for Jerseys for milk and 11, 10, and 16kg for fat. Most recent average Predicted Differences were 268, 380, and 532kg for milk and 7, 10, and 18kg for fat. Predicted Differences of natural service bulls were not overevaluated regardless of number of herds for sampling or year of entry into artificial insemination. Artificial insemination organizations can continue to acquire bulls with natural service evaluations calculated with the Modified Contemporary Comparison and be confident that these Predicted Differences are not overestimated.

Maximizing the Impact of Dairy and Beef Bulls Through Breeding Technology

Both biological and monetary considerations influence adoption of new breeding technologies. Therefore, genetic, reproductive, and economic factors that determine productivity of dairy and beef operations are reviewed. Improved sire evaluation programs, more efficient artificial insemination, and effective natural service are discussed and related to the present and future impact of dairy and beef bulls. Potential benefits of heterosis, artificial control of reproduction, improved bull management, computers, and multidiscipline research also are suggested. The dramatic impact of artificial insemination on genetic improvement and profitability of most commercial dairy herds is outlined. The uncertain expansion of beef artificial insemination is examined. Comparisons of dairy and beef industries indicate that expectation of similar results from the same animal breeding technologies are unwarranted. Dairy artificial insemination is and should continue to be economically feasible for commercial operations. Commercial beef producers will use little artificial insemination and rely on natural service bulls until precise human control of conception in the bovine is cost effective.

Factors Affecting Stability of Modified Contemporary Comparison Sire Evaluations for Milk Yield

Characteristics of early Predicted Differences for milk from Modified Contemporary Comparison were related by regression analysis to stability of evaluations over time as measured by change of Predicted Difference. Change was considered both as actual difference and as absolute difference. Bulls were required to add at least 25 daughters between early and last available evaluations. Characteristics of early evaluations included number and production of daughters and contemporaries; effective daughters per herd; number, deviation milk, and repeatability of contemporary sires; percent daughters registered and percent culled in first lactation; percent records in progress; pedigree value of the bull; and Predicted Difference for type of the bull, his sire, and his maternal grandsire. Regression models accounted for relatively little of the variation of change of Predicted Difference, suggesting that random sampling was a major cause of change. Adding type information explained much variation, but measures of type were not associated with large differences of stability. Production by daughters and contemporaries significantly influenced changes and could aid decisions by studs. Artificial insemination and natural service bulls that entered artificial insemination service had similar absolute changes and were less stable than natural service bulls remaining in natural service. The three groups did not differ for actual change of Predicted Difference.

Economic Comparison of Breeding Dairy Cows Artificially Versus Naturally

Systems analysis was used to study costs and returns of breeding dairy cows artificially or naturally. In the analysis were costs of semen, detection of estrus for artificial insemination, days open, and maintaining bulls. Also included were genetic abilities of sires, discount rates on expected returns, and probability of a female offspring reaching lactation. Transmission of genetic superiority of sires used artificially over sires used naturally to both daughter and grand-daughter was considered. Daughters of sires used artificially were superior to daughters of natural service sires by 227, 454, or 682kg (mature equivalent) milk. Breeding was started 60 days into lactation and continued for 15 cycles (21 days each) or until 90% of the cows would be expected to have conceived. Conception rate from artificial service was decreased by 5% of its rate for each subsequent breeding. For comparing artificial insemination and natural service, an initial conception rate for artificial insemination of 50%, cost of keeping a bull of $15 per cow per yr, semen cost of $8 per unit, costs for detection of estrus of $10 per cow per yr, discount rate of 10%, a 40% chance of obtaining a lactating heifer replacement per conception, a cost of an additional day open of $1.50, and income over feed costs of $.099 per kg were applied. Calving interval was 365 days for breeding by natural service. Each increase in genetic superiority of bulls used artificially over natural service bulls of 227 kg meant that the calving interval from artificial insemination could be 10 days longer with the same expected returns. Other factors in the analysis had less effect on the comparison of artificial insemination with natural service than the genetic abilities of sires. Investment in herd health (reproductive) programs to increase breeding efficiency appeared economically sound.

Relative efficiency of individual selection and reference sire progeny test schemes for beef production

Individual selection on the basis of adjusted yearling weight records (policy 1) was compared with selection of proven sires based on progeny test results ('progeny test selection'). The major assumptions in the comparisons were that herd sizes were 100 recorded cows, and that each herd used four joining groups. It was assumed that 25 herds cooperated in using two reference sires in artificial breeding to link progeny test data from young bulls in natural service, thereby increasing selection intensity without the loss in accuracy normally suffered in a single multi-sired herd. In the progeny test comparisons, preselection of young bulls for progeny testing (policy 2) was also compared with random selection among young bulls for progeny testing (policy 3). This paper contains a limited number of comparisons only, in order to indicate the possible extent of selection pressure with different policies. Comparisons in terms of annual genetic progress ranked the policies in the order 2 (greatest), 1, 3, with policy 2 being better than 3 by 90-110%. The advantage of policy 2 over policy 1 was 26-38%. In all cases, using bulls first as yearlings was preferable to 2 1/4 years in terms of annual genetic gain. With individual selection, keeping bulls for 1 year compared with 2 or 3 years had little effect on annual gain, as the rise in selection intensity balanced the rise in generation interval. Inbreeding change per year was more affected, lower rates resulting from bulls being used for 1 year only. Inbreeding rates were small with progeny test selection as described here, as long as proven sons came from young bulls as well as proven sires. The effect of selection intensity under progeny test selection with preselection becomes diluted to 25% in its contribution to annual genetic change. Thus some degree of assortative mating may be useful, or wider use of proven sires relative to young sires. With preselection the break-even number of cooperating progeny test herds was low (three herds), compared with equal rates of genetic gain from individual selection.

Sire Evaluation for Conformation of Jersey Cows

A procedure for sire evaluation was developed for Jersey type data; the model contained fixed effects for herd-year and genetic group and random effects for sires, herds-by-sires, and cows.In initial calculations artificial insemination and natural service bulls were grouped separately by year of birth with little evidence of genetic trend for final score. These evaluations then were used for pedigree indexes based on sire and maternal grandsire. Bulls of similar pedigree index for each trait were grouped for new evaluations. The correlation between pedigree index and evaluation for final score on 726 bulls with type information on sire and maternal grandsire and 10 or more classified daughters was .64. The correlation for 533 bulls with evaluation on sires only was .58. The regressions of evaluations for final score on pedigree indexes were .73±.03 and .77±.05. Predicted Difference milk had correlations of .18, .13, .55, .13, and −.04 with evaluations for final score, general appearance, dairy character, body capacity, and mammary system. Other correlations ranged from −.09 for back, rump, and tail to .20 for breed character. Correlations between these evaluations and previous estimates of genetic merit, daughter averages of latest score, were .63, .61, .54, .48, and .69 for final score, general appearance, dairy character, body capacity, and mammary system. Similar correlations for other traits ranged from .47 for breed character to .76 for stature. An index combined estimated transmitting ability for milk, fat, and final score. Bulls were ranked by indexes; different weights were used for production and type. The progress that could be expected from selection with each index was shown.

Trends in Genetic Merit of Dairy Sires at Initial Proving

Initial Modified Contemporary Comparison sire summaries from 1974 through 1978 were studied for 16,791 dairy sires of six breeds. These sires were grouped into five classes. Sires sampled through artificial insemination units were in one group; natural service sires further classified by number of herds (1, 2 to 3, 4 to 6, and 7+) in the initial (first published) proof were in the other four groups. Initial Repeatabilities of the progeny test for sires in these five classes were about 40, 18, 23, 29, and 35%.Genetic merit (pedigree indexes and Predicted Differences) was increasing over the 5 yr. Regressions of either measure of merit on year sampled averaged 19kg of milk and .6kg of fat. Bulls sampled through artificial insemination organizations were superior to natural service bulls in pedigree index and initial Predicted Difference. Genetic merit of widely sampled natural service sires showed no consistent advantage over natural service sires sampled in single herds.The initial sire summaries were compared with the most recent summary through 1978. There was a slight tendency for later summaries to average higher for all classes of sires. Sires sampled by artificial insemination organizations were more likely to increase in Predicted Difference.

Plasma hormone levels in 6-methyl-17-acetoxyprogesterone and estradiol benzoate treated heifers: Hansel, W., R. J. Schechter, P. V. Malven, K. R. Simmons, D. L. Black, A. J. Hackett & R. R. Saatman: J. Anim. Sci., [formula omitted](4): 671–681, 1975. Cornell University, Ithaca, New York, NY 14853, USA

United States Department of Agriculture Sire Summary files were used to select bulls with a published Modified Contemporary Comparison sire evaluation prior to entry into artificial insemination. Canadian bulls were not included. Of the Brown Swiss, Guernsey, Holstein, and Jersey bulls that entered artificial insemination since 1974, 28 Brown Swiss, 19 Guernseys, 298 Holsteins, and 45 Jerseys (4 to 12%) had natural service evaluations. Of these bulls, 10 Guernseys, 154 Holsteins, and 28 Jerseys had an increase of Repeatability of 30% or more after entering artificial insemination. Evaluations for bulls just prior to their entering artificial insemination were compared with their most recent evaluations through July 1983. Average Repeatabilities for evaluations of bulls just prior to their entering artificial insemination were 32% for Guernseys, 32% for Holsteins, and 31% for Jerseys and 88, 90, and 87% for their most recent evaluations. Average Predicted Differences prior to entering artificial insemination were 305 kg for Guernseys, 394 kg for Holsteins, and 452 kg for Jerseys for milk and 11, 10, and 16 kg for fat. Most recent average Predicted Differences were 268, 380, and 532 kg for milk and 7, 10, and 18 kg for fat. Predicted Differences of natural service bulls were not overevaluated regardless of number of herds for sampling or year of entry into artificial insemination. Artificial insemination organizations can continue to acquire bulls with natural service evaluations calculated with the Modified Contemporary Comparison and be confident that these Predicted Differences are not overestimated.

Milk and Fat Yield Differences for Grade Cows Sired by Artificial and Natural Insemination

Available lactations of grade cows calving between 1954 and 1969 and coded as one of five dairy breeds with identified, registered sires were screened. All herd-years having grade progeny sired by bulls in active artificial insemination service and progeny of sires not in active artificial insemination service were used. There were 819 Ayrshire, 6,834 Guernsey, 60,190 Holstein, 5,294 Jersey, and 898 Brown Swiss herd-years. Three subsets were formed for comparisons at the same age (2 yr, 3 and 4 yr, 5 yr and older) in a herd-year. Cows sired by bulls in artificial insemination service had higher yields in almost all breed-age-year subclasses, but most values, except Holsteins, were not significant. Such superiority was generally greatest in cows calving as 2-yr-olds, usually declining with age. Average milk superiorities in kilograms over all ages for 1966 to 1969 were: Ayrshire, 84; Guernsey, 71; Holstein, 57; Jersey, 53; and Brown Swiss, 65. Fat superiorities were: Ayrshire, 3.2; Guernsey, 2.5; Holstein, 2.9; Jersey, 2.7; and Brown Swiss, 3.3.Regression showed this superiority for milk increasing in only 4 of 20 subclasses; superiority increased at a declining rate in another. Superiority for fat increased in only 7 of the 20 subclasses, with superiority in 2 subclasses increasing at a declining rate. Bulls in artificial insemination studs siring grade cows were little better than bulls siring grade cows by natural service during the period.

Comparison of Estimated Daughter Superiority from Pedigree Records with Daughter Evaluation

Daughter superiorities of 240 Holstein bulls of the American Breeders Service and Eastern Artificial Insemination Cooperative (EAIC) were estimated from records of paternal sisters of the sire, dam's records, and records of daughters of the maternal grandsire. Estimated daughter superiority (EDS) was then compared with the U.S. Department of Agriculture's predicted difference for American Breeders Service bulls and with the Northeast Sire Comparison for EAIC bulls. The regression equation on estimated daughter superiority was (−84 + .561 (EDS)) kg for American Breeders Service bulls and (−227 + .654(EDS)) kg for EAIC bulls. The response is not as large as theoretically predicted but does indicate that selection of young bulls with high estimated daughter superiority is an effective method of finding a superior group of young bulls for further sampling.

Rates of Improvement by Progeny Testing in Dairy Herds of Various Sizes

Summary Rates of genetic gain in milk production by progeny testing were examined, using characteristics of Michigan Holsteins. The production records from 34,073 Holsteins on DHIA test averaged 12,237lb. of milk and 435lb. of fat (305-2×-ME). AI daughters numbered 5,098 from 187 bulls and averaged 12,305lb. of milk and 444lb. of fat. Characteristics found were: repeatability, .46 for milk, .40 for fat; heritabilities from correlations between AI paternal sisters, .31 for milk, .23 for fat; regression of future AI daughters on first n tested AI daughters, n n + 12 for milk and n n + 16 for fat; average age at calving 4.4 yr.; cows removed annually, 26.3%, one-tenth involuntarily in each of the first four lactations and one-fourth in later lactations; and heifers born which come into production, 70%. In herds of less than 100 cows, progeny testing was less efficient in improving the expected rate of genetic gain than the use of young sires selected on the basis of their dams' production. In herds of 100 and 200 cows, progeny testing had a slight advantage over the latter method. Progeny testing in AI populations of 10,000 tested cows gave possibilities of annual genetic progress of from 1.7 to 2.3% of the average annual yield, depending upon the number of sires sampled and the proportion of those sampled which are selected for service. Further improvement seems possible if the percentage of cows on test were increased and if more efficient use were made of the tested bulls in AI service.

Alterations in Specific Gravity during the Ripening of Bull Spermatozoa

Summary Determinations of the specific density of spermatozoa in ejaculates collected from normal dairy bulls in regular service were performed by centrifugation in umbradil-methylglucamine-salt solutions of different specific gravities. A negative correlation between the mean specific gravity of the spermatozoa and the frequencies of unripe spermatozoa (having a residual protoplasmic drop) was found, indicating a lower specific gravity in these than in ripe and over-ripe (non-motile) ones. The distribution of the three kinds of spermatozoa between the sedimenting and floating fractions of cells supports this conclusion, and suggests a higher specific density of over-ripe than of ripe spermatozoa. The process of ripening thus implies a continuous rise in density.

On the relationship between fertility and light-reflecting power in bull spermatozoa

The fertility of a number of ejaculates from normal dairy bulls in regular service is found to be positively correlated to the light-reflecting capacity,NE, of the spermatozoa in the ejaculates.