Maternal Ability and Genetic Ability of Birth Weight and Gestation Length

Abstract

Birth weights and available gestation lengths of 1,064 Holstein calves by 509 dams and 35 sires 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 [plus or minus] 30 lb and 278.9 [plus or minus] .35 days, respectively. The birth weight of males was 1.6 [plus or minus] .59 lb more than females and they were gestated 0.9 [plus or minus].70 days longer. Mature cows had calves which averaged 4.7 lb heavier than calves of 2-year-old cows. Calves born from Sept to March were 1.6 [plus or minus] .59 lb heavier than calves born from April thru 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, while 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.