Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/1997
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Test evaluations of dairy cattle calculated by USDA in Oct. 1996 allowed assessment of how more frequent evaluations might impact artificial insemination (AI) use of bulls. More frequent evaluations should result in less change between consecutive evaluations, earlier information for new bulls, and more timely indications of changes for marketed bulls. Of 170 Holstein bulls with a test predicted transmitting ability (PTA) protein of at least 27.2 kg, 46 had not been evaluated in July 1996. Mean PTA protein for these 46 bulls, which included the two bulls with the highest test PTA, was 30.3 kg; mean number of daughters was 20. In Feb. 1997 when the first official evaluation became available for these bulls, their mean PTA declined to 28.4 kg, and mean number of daughters increased to 40; PTA protein was 22.7 kg or more for all but 6 of the 46 bulls. For the 12 bulls not evaluated in July 1996 and with a test PTA protein of at least 31.5 kg, mean PTA was 33.6 kg for the test and 32.4 kg in Feb. 1997; corresponding mean numbers of daughters were 18 and 40. For the 124 bulls with evaluations in July 1996 and Feb. 1997, mean absolute changes in PTA protein were reduced with more frequent evaluations: 1.9 kg from July 1996 to Feb. 1997, 1.6 kg from July to Oct. 1996, and 1.3 kg from Oct. 1996 to Feb. 1997. Corresponding changes for active AI Holstein bulls were 1.5, 1.1, and 1.2 kg. Test PTA were lower for 16 of 18 bulls designated as active AI in July 1996 that had decreases of 4.5 kg or more for PTA protein in Feb. 1997. Earlier access to genetic information could increase the rate of genetic improvement in the US by allowing earlier recognition of bulls with high merit for desired traits and earlier reassessment of previously high bulls.