Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)


Male calves of all the breeds studied weighed more at birth than female calves. The birth weights of female calves were as follows: Holsteins, 89 pounds; Guernseys, 65 pounds; Ayrshires, 63 pounds; and Jerseys, 50 pounds.

There was considerable variation among individuals in their live weights. Coefficients of variation ranged from above 15 percent in calves to less than 10 percent in 2-year old heifers.

The data show that the time of first freshening marks the greatest change in the rate of growth in live weight.

Very little difference can be observed in the relative rates at which animals of the different breeds approach mature size.

Mature growth values are approached most rapidly in height at withers. This measurement is not even doubled from birth to maturity.

Holsteins, Ayrshires and Jerseys are wider in relation to depth than Guernseys.

The average weight for mature Holsteins in the Iowa Experiment Station herd may be considered as 1,405 pounds; Ayrshires, 1,111 pounds; Guernseys, 1,072 pounds; and Jerseys, 950 pounds. Gestation and lactation are shown to have considerable influence upon live weight.

Late freshening heifers weigh more than heifers calving at the usual time but after freshening the weights of both groups are quite comparable.



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