Influences on Birth Weight and Gestation Period of Holstein-Friesian Cattle

Abstract

The effects of genetic group for milk yield, breeding management, nutrition of cow, sex of calf, year and season of birth, parity, and sires within genetic groups on birth weights and gestation length were studied in 341 Hoistein-Friesian single-born calves.Least squares means and error standard deviations for birth weight and gestation length were 44.9 kg±4.5kg and 276.7 days±3.7 days. Season and year of birth did not influence both traits significantly. Male calves were 3.6kg heavier than females, but they did not differ significantly in gestation length. Calves from second and third carvings were heavier than those from first parturitions and gestated for a significantly longer time. Cows under heavy grain feeding dropped calves that were 1.8kg heavier than those under average feeding conditions; no differences in their mean gestation lengths were detected. Calves resulting from early postpartum breedings were 1.2kg lighter than those from late breedings, but their gestation lengths were not affected differentially. Calves from the high genetic group were gestated 3.4 days longer than those in the low group though they did not differ in their mean birth weight. Sires within genetic groups were a significant source of variation for gestation length in both groups, but only sires within the low group had a significant effect on birth weight. Interactions between genetic×reproduction and genetic×nutrition×reproduction were significant on birth weight whereas nutrition×sex and genetic×nutrition×reproduction interactions were significant for gestation length.A multiple regression equation for birth weight selected by a stepwise procedure included the dummy variables nutrition of cow, breeding management, sex, parity, and a second-order term in parity (squared multiple correlation = .40). The equation for gestation length included genetic group for milk yield and age at calving (squared multiple correlation .17). Sire groups accounted for 7.6 and 13.6% of the phenotypic variance of adjusted birth weight and gestation length. Paternal half-sib heritabilities were .30±.16 and .54±.22 for birth weight and gestation length.