A Study of the Birth Weight and Gestation of Dairy Animals

Abstract

Summary 1.The average weight of Jersey calves in the herd studied was 57 pounds, of Guernsey calves 64 pounds, of Ayrshire calves 72 pounds, and of Holstein calves 91 pounds. 2.The Jersey calves represented 6.3 per cent of the weight of their dams, the Guernseys 6.7 per cent, the Ayrshires 6.9 per cent and the Holsteins 7.8 per cent of the weight of their dams. 3.The male calves were 4 to 11 pounds heavier than the female calves. The average birth weight of all bull calves studied is 7.8 per cent heavier than the females. 4.Immature cows produced smaller calves than mature cows. 5.The birth weights recorded for dairy calves in the Kansas herd were consistently higher than the weights of calves reported from the Missouri and Iowa herds. 6.The nutrition of the dam had but little influence on the weight of the calf except in the case of cows on a restricted diet. In the case studied the dams on a restricted diet produced calves heavier in proportion than did well fed dams. 7.A sire may have the ability to influence the birth weight of a calf, but only to a limited degree. 8.The gestation period has no definite influence upon the size of the calf at birth. There are, however, within the different breeds, indications that the large calves are carried slightly longer than the smaller calves. 9.The average length of all the gestations studied was 282.4 days. The bulls were carried 283.2 days and the heifers 281.9. The breeds varied in the length of gestation period as follows: