Variation in efficiency of food utilization in twin calves II. The effect of live weight and feeding rate

Abstract

The relationship of efficiency to weight and feeding rate has been studied in 38 twin calves from 2 to 18 weeks of age. Following birth or weaning heavier animals were more efficient, but tended to be slightly less efficient when fully established on a diet. On balance, they possessed an advantage. Heavier twins and heavier pairs were also on average more efficient. The increase in mean efficiency for contemporary animals was about 1% for each 1 lb. superiority in weight over the 4-month period. These results contrast with the well-known decline in efficiency as animals increase in weight. Different pairs declined in efficiency with increasing live weight at distinctly different rates judged by the resemblance of twin and co-twin, but evidence for genetic control was slight. More efficient animals were associated with a relatively more rapid decline in efficiency, leading to a general convergence in efficiency as animals grew heavier. The relationship of efficiency to feeding rate was very similar to the relationship with weight.