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ARS Home » Research » Publications at this Location » Publication #144459


item Powell, Rex
item Norman, H
item Sanders, Ashley

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2003
Publication Date: 10/1/2003
Citation: Powell, R.L., Norman, H.D., Sanders, A.H. 2003. Progeny testing and selection intensity for Holstein bulls in different countries. Journal of Dairy Science. 86(10):3386-3393.

Interpretive Summary: Genetic progress in dairy cattle depends mainly on the merit of sires. Sire merit is the product of distinct steps: selection of outstanding parents, choosing a large number of young bulls with high potential to sample, accurate and rapid progeny testing (PT) of sampled bulls, intense selection of the best bulls from those sampled, and then wide use of the selected bulls. Data from national programs were used to examine the numbers of bulls sampled, merit of their sires, age and numbers of PT herds and daughters, fraction of PT bulls graduated to wide usage, and the intensity of that selection for graduation. Selection differential was calculated as the difference in estimated merit of graduates and the whole PT group. This difference was then standardized into units of standard deviation producing selection intensities that could be used to make comparisons among countries. The US, Danish , and Dutch PT bulls were younger (66 mo) at the graduate/cull time than bulls in other countries. French bulls were the oldest at 77 mo, but they require the highest amount of PT information before results are made public which would have an effect on bulls age at first evaluation. Germany, Holland, New Zealand, and Sweden all had averages per PT bull of over 100 daughters at decision time. While there were differences in quality of PT bull sires among countries, five of the top countries used similar bulls. The US ranked 4th for milk and protein and 2nd for fat. Percent graduated varied from 4 to 16 percent. Selection intensities varied among countries and often reflected significant differences in selection goals. Use of these results will allow each country to compare their programs with the others and find opportunities for improvement.

Technical Abstract: International Bull Evaluation Service Holstein evaluations from February 1995 through August 2002 were used to determine characteristics of progeny testing for Holstein bulls in Australia, Canada, Denmark, France, Germany, Great Britain, Italy, The Netherlands, New Zealand, Sweden, and the United States. Decision to graduate a bull from progeny test into widespread use was assumed to be made at the time of the second evaluation. Mean bull age at decision varied across countries by nearly a year. Mean numbers of herds and daughters showed a wide range: 39 to 186 and 54 to 197, respectively. These results were affected by the national policies on what constitutes an official evaluation. Countries with higher requirements (herds, daughters, or reliability) generally had higher means for those statistics and higher age at decision. Mean estimated breeding values for yield traits of sires of tested bulls were most similar across countries for fat, differing by only 8.1 kg. The three countries highest for milk differed only by 16kg, however the overall range was 376 kg. Percents of bulls graduated ranged from 4 to 16. Selection intensities (standardized selection differentials) tended to be about 1.0 for yield traits. Selection intensities for somatic cell score were generally unfavorable, indicative of selection for negatively correlated yield traits. Reflecting the varying breeding goals of individual countries, selection intensities for stature were positive for most countries and most negative for New Zealand. With a few exceptions, selection intensity for fore udder EBV was not as high as for other traits, with seven of 11 being within +/- 0.12. All but one country showed positive selection for udder support. Breeding programs change over time and these results reflect past rather than current selection. These statistics permit comparison of the components of progeny test programs across country indicating the best that was being achieved, thereby suggesting opportunities for improvement.