Progeny-tested Bulls Research Articles

Effects of method of embryo production and transfer on pregnancy rate, embryo survival rate, abortion and calf production in beef cows

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.

Germ Cell Weakness as a Cause of Testicular Hypoplasia in Bulls

Sporadic cases of testicular hypoplasia were earlier found in bulls of the Swedish Red and White breed. An accumulation of cases have occurred since 1970 in sons of 2 outstanding progenytested bull sires, 2 F and 27 U, which had a common father, 545 B. The history and clinical examination of affected bulls varied. Some had azoospermia and very small testes at a young age, while others could be normal in all respect when they were young but had a short reproductive life and had to be culled at about 3 years of age. Most of the affected bulls were between these 2 extremes. The histologic examination showed principally different degrees of testicular degeneration. There were always some germ cells left in all affected seminiferous tubules indicating that there was not a lack of germ cells causing the hypoplasia. Germ cell weakness is obviously a hereditary condition. The sires 545 B, 2 F and 27 U had a relatively low fertility. In their pedigree were several bulls known to have had a low fertility. No sons of 2 F and only a few sons of 27 U were used for A.I. services and at present only few cases of testicular hypoplasia are seen.

Progeny testing bulls for susceptibility to facial eczema

Abstract During the severe facial eczema (FE) outbreak in autumn 1989, 65 Jersey bulls were ranked on the susceptibility to FE of their 2-year-old daughters, as recorded in 43 affected herds. The criterion of susceptibility was elevation of the enzyme gamma-glutamyltransferase (GGT) to levels above the normal range. Five of the highest ranked and five of the lowest ranked bulls were then mated to cows at Ruakura. Seventy-four experimental calves were born to these matings and reared in 1990. At 3.5 months of age and an average 94 kg liveweight, they were challenged with sporidesmin, the mycotoxin causing FE, at a dose rate of 0.3 mg/kg liveweight. Calves were slaughtered at either 36 or 43 days after dosing. The loge GGT values, weekly from 1 to 6 weeks after dosing, averaged 5.08 and 4.50 units for “High” and “Low” bulls respectively (SED 0.30; P < 0.10). The difference of 0.58 units in this experiment can be compared with a difference of 0.56 in the 1989 study, indicating that the original field test wa...

Genetic and Economic Evaluation of Nucleus Breeding Schemes for Commercial Artificial Insemination Firms

Genetic and economic aspects of adoption of a multiple ovulation and embryo transfer nucleus breeding scheme by a commercial AI firm were investigated. Selection for a lactation trait in a large dairy cattle population with a competitive semen market served by five AI firms was simulated using a semi-stochastic model. Returns were from sale of semen from progeny-tested bulls, discounted to the time of adoption of the new scheme. Comparisons were to an effective conventional program using multiple ovulation and embryo transfer to produce young bulls. Sires of bulls and nucleus females were selected from progeny-tested bulls across AI firms. Therefore, rates of inbreeding within the nucleus were small. Closed adult nucleus schemes were competitive to the conventional scheme only for large nucleus sizes. Open adult schemes increased present values of returns from 20 yr of selection by 10 to 20%. Further cost analysis is needed to determine their economic profitability. Juvenile nucleus schemes increased present values of returns but also risks on returns. Relative gains in returns increased from 8 to 16% for the first 4 yr of selection to 46 to 63% for the first 20 yr. Additional returns from opening the nucleus were small due to high genetic superiority of the nucleus. Additional returns from repeated, instead of one-time, selection of females as donors were similar to returns from a 50% increase in nucleus size. Additional returns from eligibility of young bulls as bull sires were small due to the small number of young bulls selected.

Genetic Changes in Protein, Milk, and Fat Yields as a Response to Selection for Protein Yield in a Closed Population of Holsteins

Three estimators of intrapopulation genetic change were used to quantify response to selection for protein yield in first lactations, of Holsteins from three herds of the Research Branch of Agriculture Canada. Selection began in 1972 and continued through 1985. For the first 3 yr (1972 to 1974), foundation cows were mated by AI to young bulls from the foundation herds and to progeny-tested bulls available in US and Canadian AI units. Progeny-tested bulls produced in this closed herd selection project were not available for selection before 1978. A mixed model analysis based on sire merit revealed an apparent curvilinear response to selection with the most pronounced improvement occurring during the last 5 yr. Sons produced by progeny-tested bulls selected within the project in 1978 and 1979 were superior to the progeny-tested bulls from AI units used in the foundation matings. This sire superiority for protein, milk, and fat yield was 7.3, 193.6, and 7.1kg, respectively. Genetic trend in the cow population was estimated by two regression procedures. Estimates of annual gain for protein yield were 1.0 and 2.2kg and protein equivalent to .7 and 1.8% of mean yield. Corresponding estimates of correlated responses were 45.9 and 68.6kg milk and 1.3 and 2.3kg milk fat.

Genetic and Phenotypic Parameters for Production and Days Open in the First Three Lactations of Swedish Dairy Cattle

Abstract The material consisted of completed 305-day records of daughters of Al bulls. The analyses were carried out for each of the two predominant breeds where one of the breeds was divided into two separate geographical areas. The material was further divided into five years of first calving (1977–81) giving a total of 15 data sets. The traits were 305-day lactation milk (M) or fat (F) yield and days open (DO) in the first three lactations (1, 2, 3). All traits were preadjusted for month and age of calving, production was also adjusted for days open. The multiple trait mixed model used had the same effects for all traits analyzed simultaneously. These were effects of herd (fixed), group (fixed) and sire within group. The latter was random if the sire was a young bull and fixed for old progeny-tested bulls. The fixed sires were not used for estimating variance components. A triangular transformation was applied which made the residual variance-covariance matrix an identity matrix. The EM-algorithm was used to get approximate REML estimates of the variance components. Forty rounds of iteration were carried out. Overall average h 2 for milk yield were 0.268, 0.246 and 0.248 for the first three lactations respectively. The genetic correlations between the lactations were high, 0.855, 0.836 and 0.966 for r g12, r g13 and r g23 respectively. Heritabilities for fat yield were somewhat lower: 0.250, 0.213 and 0.228 respectively. Genetic correlations were 0.920, 0.846 and 0.938 respectively. For days open low heritabilities were found: 0.040, 0.050 and 0.066 respectively. Fairly high genetic correlations were found between these traits, however: 0.582, 0.493 and 0.220. Genetic correlations between milk yield in first lactation (Ml) and days open in first and second lactations (DO1, DO2) were moderately high and unfavourable: 0.414 and 0.335 respectively. There were no systematic trends in the estimated parameters over the different production years. The unfavourable genetic correlations obtained in this study between milk production and days open was not reflected in the estimated genetic trends for days open in a previous study.

Effects of Selection for Body Size on Feed Efficiency and Size of Holsteins1,2

First lactation records from a herd of Holstein cows bred for either high production and large size or for high production and small size were examined to estimate effects of selection for size and feed efficiency. Selection was among progeny-tested bulls available from the artificial insemination industry. Three rations were fed that differed for ratios of concentrate to milk. After three generations, groups of cows bred for large or small size differed by 50.2kg in weight, 5.6cm in wither height, 6.4cm in length, 2.1cm in depth, and 5.9cm in chest circumference; most differences were due to a decrease in the size of the small cows. On the basis of total lactations, cows bred for small size were 2.8% more feed efficient than cows bred for large size. During the first 90 d of lactation cows fed the low concentrate ration were more efficient than those fed the high concentrate ration. Season of calving had an effect on feed efficiency between d 30 and 120 of lactation. During this period cows calving between December and May were more efficient.

USE OF SIB TESTING AS A SUPPLEMENT TO PROGENY TESTING TO IMPROVE THE GENETIC MERIT OF COMMERCIAL SEMEN IN DAIRY CATTLE

Groups of sibs, sisters to bulls being bred for progeny testing, can be produced by multiple ovulation and embryo transfer (MOET). Sib tests are complete at 3 yr of age, and progeny tests when bulls are about 5.5–6 yr of age. The merit of commercial semen could be increased by using the bulls with the highest estimated breeding values from both the sib test group and the progeny test group rather than only from the latter. With current selection rates (20%) among progeny-tested bulls for commercial use, current genetic trend (0.1 SD units per year) in bulls and with the equivalent of 3–7 full sisters per bull, the relative genetic superiority of semen from the combined groups could be from 1.10 to 1.20 times that from the progeny-tested group alone. Key words: Embryo transfer, sib testing, progeny testing, commercial semen

COMPARISON OF FINNISH AND CANADIAN AYRSHIRE PROVEN BULLS

Semen from four Finnish and four Canadian progeny-tested Ayrshire bulls was used to breed cows and heifers in 50 cooperating Ayrshire herds in Quebec and Ontario in 1972 through 1974. Among the 690 calvings, 2.5% were stillbirths, 2.0% were difficult, 1.1% were malpresentations and 11.4% were unobserved. The percent easy calving among live births was 97% with no significant difference between bull groups or sex of calf. Male calves average 36.4 kg at birth compared with 34.7 kg for females. In the Quebec data, 69% of calvings were to the first service, 23.7% to the second service and 7.2% to a third or later service with no significant difference between bull groups. Heart girth and withers height before calving averaged 164 cm and 119 cm, respectively, in Quebec herds at an average age of 24.6 mo. In Ontario herds, heart girth and withers height after calving averaged 177 cm and 126 cm, respectively, at an average age of 31.6 mo. Taped weight at first calving averaged 420 kg in Quebec herds. None of the measurements of growth showed significant (P &gt; 0.05) differences between groups, although there were significant (P &lt; 0.05) differences among bulls within group. BCA milk and fat averaged 141 and 139, respectively, with a 4.1 ± 3.5 and 4.5 ± 3.3 BCA superiority for Canadian sires in milk and fat, but these differences were not significant (P &gt; 0.05). Mature equivalent protein yield in Quebec heifers averaged 180 kg with a superiority of 10.0 ± 8.5 kg for Canadian sires. Differences between the Finnish and Canadian bulls tested for calving ease, growth and lactation performance were not significant. For conformation, Canadian-sired heifers scored significantly higher (P &lt; 0.05) for final score and all 10 scorecard components and were significantly (P &lt; 0.05) larger, taller, more stylish and more rapid in milking out. No evidence was found to justify extensive use of Finnish Ayrshire bulls in the Canadian population. Key words: Dairy cattle, Ayrshire, Finnish, Canadian, Sire comparison

Selection for fertility on the basis of AI data

The present contribution is a review of earlier studies on genetic aspects of bull fertility as measured by non-return rate when used for AI. The conclusions may be summarised as follows. 1. (1) Conception rate and calving interval are determined by the fertility of the bull and the fertility of the cow jointly. One unit of genetic improvement in male fertility is therefore of equal importance to one unit of improvement in female fertility. 2. (2) The heritability of bull fertility, as measured by the non-return rates from a few hundred inseminations, is large enough to provide a basis for efficient selection. The genetic standard deviation is, however, considerably less for male than for female fertility. 3. (3) The genetic correlation between male and female fertility is slight, and the same holds true for the genetic correlation between male fertility and milk production. 4. (4) In the final selection of progeny-tested bulls, due attention should be given to the estimated breeding value of the bull with respect to male fertility as well as to female fertility.

Comments on statistical efficiency in bull progeny testing for calving difficulty

The analysis of Mahon and Cunningham, 1976 ( Livest. Prod. Sci., 3: 147–153) on progeny testing bulls for calving difficulties and associated binomial traits is reviewed. They concluded that there was very little difference in efficiency between testing on heifers and cows or between testing on breeds of high and low incidences of calving difficulties, but they ignored the expected variance between sires. The intra-class correlation among progeny groups and heritability of such traits increases with increase in incidence, as predicted on a model of continuous underlying liability with a threshold. Therefore efficiency of testing should increase as the incidence rises.

The progeny testing of dairy bulls at different levels of production

1. An analysis has been made of milk records from 13,000 cows bred by artificial insemination in Denmark.2. The herds were divided into three equal groups on the basis of their average production. The variance of yield within herds increased as the average yield increased, but the coefficient of variation declined slightly. The genetic variance was more than five times as large in the high-yielding herds than in the low, and correspondingly the heritabilities in low, medium and high herds were 0·05, 0·15 and 0·22 respectively. These were estimated from the variation observed between progeny groups of the same 152 bulls at each production level.3. No evidence was obtained of any sire-herd interaction for yield, either within or between management levels. The true ranking of bulls for breeding value was apparently the same at all levels.4. The heritability of fat content in the three groups was 0·27, 0·47 and 0·49 respectively, and no evidence of sire-herd interaction was found.5. The contemporary comparison method of assessing A.I. bulls for yield was found to have the accuracy expected in theory.6. These results are discussed in relation to those of other workers with which there are some discrepancies. On our results, a policy of choosing bulls on the basis of their daughters' performance in high-yielding herds should be the most satisfactory way of progeny-testing bulls used in artificial insemination.