Abstract
Six Holstein heifer calves weaned at 45 days-of-age were randomly allocated into high daily gain (1.1 kg/d, HDG) and low daily gain (0.56 kg/d, LDG) groups, and were slaughtered at 170 kg of live weight. Energy intake level in the feeding period was 2.4 $\times$ maintenance in 105 days for HDG and 1.4 $\times$ maintenance in 216 days for LDG calves. Total length of the small intestine was identical between groups, but both weights of the pancreas and of the small intestinal mucosa were greater (p < 0.01) for HDG calves. Alpha-amylase, lipase, proteinase, and trypsin activities of the whole pancreas were higher (p < 0.05) in HDG calves. Disaccharidase activity of the whole small intestinal mucosa was also higher (p < 0.10) for HDG than for LDG calves. However, the enzymatic activities, expressed as per gram or per protein of the pancreas and the small intestinal mucosa, were not affected (p > 0.10) by the plane of nutrition. These results suggest that the digestive enzyme activity in the small intestine varies primarily with the weight of tissues synthesizing the enzyme.