RELATIONSHIP OF LINEAR TYPE TRAITS AND HERD LIFE UNDER DIFFERENT MANAGEMENT-SYSTEMS

The relationship of conformation traits, particularly locomotive traits, and herd life under different management systems was investigated. Herd life to 84 mo was regressed on measures of linear type and production for 139,998 cows in 6277 herds. Linear traits accounted for 14% of explained variation for herd life after effects for herds and production were considered. Udder traits explained more herd-life variation than other conformation traits. Fore udder attachment and udder depth explained the most variation when production was included in analyses. Udder depth explained the least amount of herd-life variation among six udder traits when production was not included in the analyses. The relationship between locomotive traits and herd life differed by type of housing. Cows with intermediate curvature of the rear legs had longer herd life in all housing types, but the absolute difference between optimum and extreme was greater for cows in confinement than for cows in loose housing. Relationship between cows' genetic merit for curvature of the rear legs and herd life, however, was near zero. Cows with steeper foot angles had longer herd life in all housing types. Regressions of herd life on nonlocomotive type traits for different housing systems were always greater for cows in tie-stall environments compared with cows in loose housing. Personal preference for type traits by dairy producers within housing systems may partly explain herd-life results.