Heritability of Hypocalcemia at First Parturition in Norwegian Cattle: Genetic Correlations with Yield and Weight

Abstract

Minimum plasma calcium level around parturition and its relation to BW at parturition, milk yield, and weight change in mo 1 of lactation were studied in 334 first lactation Norwegian cows. Minimum plasma calcium level was reached 18 to 30 h postpartum. Single observations for all animals were fitted with a multitrait animal model including all genetic relationships. Heritabilities of the traits were calcium postpartum, .11; milk yield, .35; BW, .65; and weight change, .17 with standard errors about .10. Genetic correlations between calcium postpartum and the other traits were milk yield, –.49; BW, –.66; and weight change, .42 with standard errors about .25. Environmental factors with detectable effect on hypocalcemia were age at parturition and calving season. Regression of calcium postpartum on age was –2.66 × 10–4 mmol/L per d. Calvings shortly after the pasture season were related to higher calcium postpartum than calvings after 3 to 4 mo with indoor feeding. © 1991, American Dairy Science Association. All rights reserved.