Factors Affecting Calf Livability for Holsteins

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Abstract
A total of 136,775 records from Holstein calvings was obtained from the National Association of Animal Breeders. Calf mortality (scored as dead at birth plus dead by 48 h) was greater for males (7.6%) than for females (5.6%). First parities of dams showed about 2 times as much calf mortality as later parities (10.5 vs. 5.6%). Relationship was nonlinear between calf livability and size of calf, regardless of parity-of-dam and sex-of-calf effects. Dead calves averaged 1.2 days shorter gestation than live calves (279.6 days). Sex of calf, parity of dam, and linear and quadratic gestation length affected calf livability when the model also included sires. Percentage of calf mortality of progeny of individual sires ranged from 1 to 16% for sires with at least 60 progeny. Mixed model estimates of heritabilities of livability were 1.02% (when coded as 1-alive at 48 h, 2-dead at birth and 3-dead within 48 h) and 1.54% (when coded as 1-alive, 2-dead by 48 h). Heritability decreased 26% when gestation length was ignored. Attempts to normalize scores did not improve estimates of heritability. Heritability for livability was small.