Maternal Ability and Genetic Ability of Birth Weight and Gestation Length

Birth w~,ights and available gestation lengths of 1,064 ttolstein calves at the Southern Michigan Prison, Jackson, Michigan, were analyzed to determine the effect of differences in nmtermfl ability and genetic ability. The average birth weight and gestation length was 97.4 .30 lb and 278.9 .35 days, respectively. The birth weight of males was 1.6 .59 lb more than females and they were gestated 0.9 .70 days longer. Mature cows had calves which averaged 4.7 lb heavier than calves of 2-yr-old cows. Calves born from September to March were 1.6 .59 lb heavier than calves born from April through August.