Abstract
The objective of this study was to evaluate different combinations of one-carbon metabolites [OCM: rumen-protected methionine (RPM), rumen-protected choline (RPC), folate (FA), vitamin B(12) (B(12))] on pancreatic and jejunal carbohydrase activity at d 14 of the estrous cycle in beef heifers. Thirty Angus heifers were fed a high-roughage diet and assigned to treatments: 0% RPM + 0 g/d RPC + saline injection (0XNEG), 0.08% RPM + 60 g/d RPC + saline injection (0XPOS), 0.08% RPM + 60 g/d RPC + 80 mg FA + 5 mg B(12) (0.5X), 0.08% RPM + 60 g/d RPC + 160 mg FA + 10 mg B(12) (1X), or 0.08% RPM + 60 g/d RPC + 320 mg FA + 20 mg B(12) (2X). Dietary treatments were fed for 14 d and FA and B(12) injections were given on d 0 and 7 of the estrous cycle with tissues collected on d 14. The effect of RPM+RPC supplementation was evaluated using a contrast statement comparing 0XNEG vs. others. Polynomial contrasts were used to determine effects of FA+B(12) dose. Protein concentration and carbohydrase activities of the pancreas and jejunum were not influenced (P≥0.21) by RPM+RPC supplementation. Pancreatic protein concentration responded cubically (P< 0.01) to FA+B(12) dose where pancreatic protein concentration was lesser for 0.5X compared with other treatments. Likewise, pancreatic α-amylase activity responded cubically (P< 0.01) to increasing FA+B(12) dose because pancreatic α-amylase activity was lesser for 0.5X (182 U/g) compared with 0XPOS (350 U/g), 1X (347 U/g), and 2X (412 U/g). Jejunal protein concentration and maltase and glucoamylase activities were not influenced (P≥0.29) by FA+B(12) dose. Jejunal isomaltase activity tended to decrease linearly (P=0.07) with increasing FA+B(12) dose. These findings suggest that the balance of different OCM could be important for regulation of pancreatic protein turnover and α-amylase activity. USDA is an equal opportunity provider and employer.