Dietary carbohydrate source and energy intake influence the expression of pancreatic alpha-amylase in lambs

In ruminants, pancreatic alpha-amylase is the primary enzyme responsible fo r the initial hydrolysis of alpha-linked glucose in the small intestinal lu men. The objective of this experiment was to examine the effects of altered dietary starch and energy supply on the expression of pancreatic alpha-amy lase mRNA, protein and activity in lambs. Wether lambs (n = 24; 28 +/- 0.5 kg body weight) were fed low or high starch diets at 1.2 or 1.8 x net energ y of maintenance for at least 28 d before tissue collection. Lambs fed the high energy/high starch diet tended to have more pancreatic alpha-amylase p rotein (54.5 kDa; P = 0.08) and had greater activity (P = 0.03), but alpha- amylase mRNA (1.6 kb) tended to be lower (P = 0.17). Additionally, rumen fl uid total short-chain fatty acid concentration was greater (P = 0.04) and p lasma glucose concentration tended to be greater (P = 0.07) in lambs fed th e high energy/high starch diet. However, pancreatic trypsinogen protein (25 .5 kDa) and jejunal maltase activity were not influenced by dietary treatme nt, suggesting that different regulatory systems are involved in regulating the tissue protein or activity levels of these two enzymes compared with a lpha-amylase. These data suggest that dietary regulation of pancreatic alph a-amylase expression in ruminants is complex and probably regulated by tran scriptional and post-transcriptional events.