Submitted to: Journal of Dairy Science
Publication Type: Abstract only
Publication Acceptance Date: 2/28/2005
Publication Date: 7/24/2005
Citation: Van Raden, P.M., Tooker, M.E. 2005. Productive life including all lactations, longer lactations, and calf value [abstract]. Journal of Dairy Science. 88(Suppl. 1):378. Interpretive Summary:
Technical Abstract: Longer lactations are more profitable than in the past, and daughter pregnancy rate evaluations now allow separate selection for cow fertility and longevity. Measures of productive life were compared and updated life expectancy factors were derived to replace those estimated in 1993. Extra credits for lactations longer than 10 mo and beyond 84 mo of age are proposed, and also for each calf produced so that an extremely long lactation will not receive more credit than multiple shorter lactations with dry periods between. Maximum credits per lactation of 10 mo, 12 mo, and unlimited were compared; the latter included a calf value equal to 2 mo of production. Days in milk beyond 305 had not been stored in early data but were estimated from the subsequent calving date assuming a 60-d dry period. Heritabilities and genetic correlations were estimated by multi-trait REML for longevity censored at various ages and for yield traits and somatic cell score in first parity. Data included records from 1,098,329 Holsteins born from 1994 through 1997 from 5109 sires, and a relationship matrix among sires was included in the model. Cows that were still alive in 2005 received credit for predicted remaining months of productive life. Lactations beyond 84 mo added little information. Heritability of productive life was 0.073 with 10-mo, 0.069 with 12-mo, and 0.068 with unlimited lactation credits. Corresponding genetic correlations of productive life with protein yield were 0.00, 0.03, and 0.11, all much lower than the 0.46 estimated in 1993. Phenotypic correlations and life expectancy factors were similar to 1993 estimates. Productive life censored at 36 mo is genetically correlated by only 0.87 with final productive life and is influenced more by yield traits (those correlations ranged from 0.14 to 0.27). Adjustments for yield could make correlations more consistent across time and across censoring ages. Stable properties and high economic value are desired while retaining simple interpretation.