|Lawlor, Jr, Thomas|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/1998
Publication Date: N/A
Citation: Interpretive Summary: Genetic evaluations for length of productive life based on actual Dairy Herd Improvement Association culling data have been available in the United States since January 1994. Although substantial genetic variation in productive life exists, the reliability of selection is often low, particularly for recently progeny-tested bulls with daughters that have not yet had an opportunity to be culled. Correlated production and conformation traits, which have higher heritabilities than productive life and are available earlier in life, may be used to enhance productive life evaluations of young bulls that have little or no direct culling information available. Genetic correlations between productive life and milk, fat, dairy form, and udder traits ranged from +.22 to +.46. Maximum reliability of indirect prediction of productive life from 16 correlated type and production traits was .56, and maximum reliability from a subset of 10 traits was .51. Indirect information about productive life that was derived from type and production traits was combined with actual culling information to increase the total amount of available information for many recently progeny-tested bulls. The procedures for enhancing direct evaluations for productive life of dairy sires with indirect information about production and type were implemented by the USDA Animal Improvement Programs Laboratory and Holstein Association USA in July 1994.
Technical Abstract: Productive life (PL) of dairy cattle can be measured as the length of time between first calving and culling from the herd. Genetic selection for increased PL is expected to result in improved general health, production, and reproduction, which can increase dairy farm profitability by decreasing the number of replacement heifers needed, by allowing rearing costs to be dispersed over a longer time period, and by increasing the number of cows producing at a mature level. However, the heritability of PL is low, and many recent bulls have few offspring with culling data. Therefore, the accuracy of genetic evaluations for PL is low for many important bulls. This study developed a simple procedure to combine direct PL information from Dairy Herd Improvement Association culling data with indirect PL information from correlated production and type traits to obtain more accurate early predictions of genetic merit for PL of dairy bulls. This procedure was implemented by USDA's Animal Improvement Programs Laboratory and Holstein Association USA in July 1994. The resulting PL evaluations will enable dairy producers to make more accurate breeding decisions when selecting cows to remain productive longer, thus increased production efficiency and reducing health problems.