Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/1997
Publication Date: N/A
Technical Abstract: Long productive life (PL) is a primary breeding objective of dairy farmers. Various tools, of which type traits are the most popular, aid farmers in obtaining efficient, high producing, sustainable cows. Genetic correlations were estimated between length of PL and type traits for Quebec Holstein cows. The original data from Quebec s Dairy Herd Analysis Service contained 443,143 lifetime records calculated from 1,592,661 lactation records including 1979-95 calvings; 517,051 type trait records were received from the Holstein Association of Canada. A total of 212,664 cows had a lifetime production and a type classification record. Data were divided by opportunity for the cow to live to 17, 30, 43, 55, and 96 mo of PL. A sire model was fit to estimate genetic correlations between lifetime and type traits. Two herd life (HL) variables were used for each data set: true HL and functional HL. Functional HL was computed by including a covariable to reflect 1st lactation milk deviation of a cow from her herdmates, which allowed estimation of genetic correlations independent of yield. Heritabilities for survival to 17, 30, 43, 55, and 96 mo of true (functional) HL were .04 (.03), .06 (.03), .07 (.05), .05 (.04), and .07 (.06). When accounting for 1st lactation milk yield, traits with highest correlations with PL were mammary system, fore udder, rear udder, final score, fore udder attachment, and feet and legs. For true HL data sets, traits with highest correlations with PL were dairy capacity, final score, fore udder, rear udder, and texture. The trait with the greatest differences between functional and true HL correlations was dairy capacity. Correlations between true HL and dairy capacity were .29-.49; for functional HL, the correlation was close to .00.