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Title: HISTORICAL EXAMINATION OF CULLING OF DAIRY COWS FROM HERDS IN THE UNITED STATES

Author
item Norman, H
item HARE, E - FORMER AIPL POSTDOC

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2005
Publication Date: 7/24/2005
Citation: Norman, H.D., Hare, E. 2005. Historical examination of culling of dairy cows from herds in the United States [abstract]. Journal of Dairy Science. 88(Suppl. 1):122.

Interpretive Summary:

Technical Abstract: Dairy producers need cows that reproduce, stay alive, and produce well, but information on culling rate and herd life has not always been readily available so that producers can minimize cow losses. A recent examination of cow survival in Dairy Herd Improvement herds provided information on culling rate since 1980. Cows were excluded if the herd discontinued testing during their productive period or they were sold for dairy purposes. Survival rates for individual parities were the fraction of cows with an opportunity to calve that did calve. Number of parities by breed and year of first calving was determined to provide an indicator of herd life before culling. Survival rates for second through eighth parities were 73, 50, 32, 19, 10, 5, and 2%, respectively, for Holsteins. Survival to second parity was 72% for Ayrshires, 69% for Brown Swiss, 66% for Guernseys, and 75% for Jerseys; corresponding survival to fifth parity was 22, 23, 15, and 26%. Although survival to second parity declined only slightly after 1980, survival to later parities dropped substantially. Survival rates for Holsteins were 77, 57, 39, 24, 14, 8, and 4% in 1980 for second to eighth parities but declined to 74, 49, 28, 16, 8, 4, and 1% in recent years. Mean number of parities declined from 3.2 for Ayrshires, 3.2 for Brown Swiss, 2.8 for Guernseys, 3.2 for Holsteins, and 3.4 for Jerseys that first calved in 1980 to 2.9, 2.9, 2.4, 2.8, and 3.2 for cows that first calved in 1992. Across calving years, about 36, 26, and 17% of Holsteins were first-, second-, and third-parity cows, respectively. Mean calving age ranged from 44 mo for Guernseys to 49 mo for Brown Swiss, a decline from earlier estimates, and recent years show a continuing decline. The increase in culling rate and subsequent reduction in mean calving age must be driven by dairy management choices rather than a decline in genetic merit of the population as genetic estimates indicate that substantial genetic improvement is being made in productive life.