Maternal Ability and Genetic Ability of Birth Weight and Gestation Length

Abstract

Birth weights and available gestation lengths of 1,064 Holstein calves at the Southern Michigan Prison, Jackson, Michigan, were analyzed to determine the effect of differences in maternal ability and genetic ability. The average birth weight and gestation length was 97.4±.30lb and 278.9±.35 days, respectively. The birth weight of males was 1.6±.59lb more than females and they were gestated 0.9±.70 days longer. Mature cows had calves which averaged 4.7lb heavier than calves of 2-yr-old cows. Calves born from September to March were 1.6±.59lb heavier than calves born from April through August.Heritability of birth weight was 0.22 and of gestation length was 0.10. The genetic correlation between birth weight and gestation length was 0.57. The correlations between the genie ability for either birth weight or gestation length and the genie maternal ability for the same trait was −.93 for both traits. The heritability for maternal ability of gestation length was 0.05, whereas the heritability for maternal ability of birth weight was 0.04.The heritability of birth weight and gestation length may be smaller than the calculated heritability for each trait, due to negative genetic correlation with maternal ability.