Indirect prediction of herd life in Guernsey dairy cattle.

Production and type data were used to investigate the relationships of these traits with herd life data in US Guernsey cows that calved from 1985 through 1990. Two definitions of herd life were used: actual days from birth to disposal (true herd life) and herd life adjusted for milk production (functional herd life). Genetic parameters were calculated with data from cows that had an opportunity to reach 84 mo of age (n = 18,725). Linear type traits were preadjusted for stage of lactation and age at classification. True herd life was preadjusted for age at first calving and for functional herd life, within herd-year quartile ranking for milk yield. The (co)variance components for true and functional herd life, milk, fat, protein, and 15 linear type traits were estimated with multiple-trait REML in an animal model. Heritability estimates for true and functional herd life were 0.12 for both traits. Estimated genetic correlations of herd life with body size traits were from -0.14 to -0.29, with feet and leg traits were from -0.10 to 0.06, and with udder traits were from -0.09 to 0.24. These correlation parameters were used for indirect prediction of herd life from available production and type information in Guernseys.