The Effect of Pregnancy on the Body Weight of Dairy Cows

Abstract

Summary 1. A study was made of the effect of pregnancy on the body weights of 56 Ayrshire cows during the first three periods of gestation. 2. The body weights showed a definite pattern of increase as the stage of pregnancy advanced. 3. The gain in weight over and above normal weights was not great before the fifth month of pregnancy. From 75 per cent to 85 per cent of the gain came in the last four months of pregnancy. 4. The gain in weight from month to month was much more uniform with first-calf heifers than with the older animals. This was probably because the heifers were still growing and not producing milk. 5. The average monthly gains made during the eighth month of pregnancy was less than in the months immediately preceding and following. 6. The animals in the last month of pregnancy were on the average 151 pounds heavier than open heifers at the same age. During the first pregnancy they were 142 pounds heavier; during the second pregnancy, 148 pounds heavier; and during the third pregnancy, 162 pounds heavier.