|Wright, Janice - Jan|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/17/2006
Publication Date: 7/9/2006
Citation: Norman, H.D., Wright, J.R. 2006. Factors that impact longevity of Holsteins in the United States [abstract]. Journal of Dairy Science. 89(Suppl. 1):276(abstr. 348). Interpretive Summary:
Technical Abstract: Region, herd size, inbreeding, and performance were examined to determine their impact on longevity of 8 million US Holsteins from 1980 through 2005. Seven geographical regions (5 to 9 states each) were defined. Ten inbreeding groups were defined based on percentage of inbreeding: 0, 0.1 to 1.0, 1.1 to 2.0, 2.1 to 3.0, 3.1 to 4.0, 4.1 to 5.0, 5.1 to 7.0, 7.1 to 10.0, 10.1 to 15.0, and >15.0. Seven herd-size groups were defined: <50, 51 to 100, 101 to 200, 201 to 500, 501 to 1,000, 1,001 to 2,000, and >2,000 cows. Cows were excluded if sold for dairy purposes or if the herd discontinued testing during productive herdlife of the cow. Time restraints were imposed so that cows had an opportunity to survive to parity 8. Differences in number of calvings for the most recent year with complete data were notable between regions; number of calvings ranged from 2.59 (Southeast) to 2.92 (Northeast). Differences based on herd size were smaller; number of calvings ranged from 2.75 (101 to 200 cows and >2000 cows) to 2.83 (<50 cows and 501 to 1,000 cows). Inbreeding coefficients have increased over time, and inbreeding had a large impact on number of calvings and productive herdlife. For the latest year with survival opportunity, mean number of calvings decreased with increasing inbreeding from 2.97 calvings at 0% inbreeding to 2.53 calvings at >10% inbreeding. First-parity yield traits (milk, protein, and fat) had greater impact on cow longevity than did region or herd size. For terminal records, lactations were shortest for cows with mastitis or high somatic cell score (197 d) or that died (200 d) and longest for cows with reproductive problems (389 d). Cows that were culled after early parities had longer lactations than those culled after later parities. As cows aged, fewer were sold because of low yield or poor reproduction, and more died or were culled because of mastitis and high somatic cell score.