Effects of choline on blood metabolites associated with lipid metabolism and digestion by steers fed corn-based diets1

Abstract

Ruminally cannulated steers (281 +/- 18 kg) were used to evaluate effects of choline on digestion and metabolism. Four steers were implanted with 24 mg of estradiol and 120 mg of trenbolone acetate, and four steers were not implanted. Cattle were assigned to concurrent 4 x 4 Latin squares. Dietary treatments were a 2 x 2 factorial: 0 or 4% tallow (DM basis) in corn-based diets, and 0 or 5 g/d supplemental choline administered abomasally. Blood collected before and 6 h after the initial choline infusion was used to assess acute responses to choline. Digestibility and blood metabolites were measured after adaptation to choline, as well as after an abomasal dose of 100 g of lipid. Digestibilities of dietary DM (P = 0.29) and of dietary total fatty acids (P = 0.42) were not affected by choline. Apparent digestibilities of C18:0 and C18:1 fatty acids were greater (P < 0.05) when diets contained 4% tallow. Digestibilities of fatty acids in the lipid dose were less than those in the diet, and no biologically important differences in fatty acid disappearance resulted from the treatments. No significant acute responses to choline were detected. After adaptation to choline, no important differences in plasma metabolites occurred in response to choline infusion. Plasma urea was less (P < 0.05) for implanted cattle, reflecting increased deposition of protein. Plasma cholesterol was greater (P < 0.05) for steers fed 4% tallow. Changes in plasma triglycerides in response to an abomasal lipid dose were less (P < 0.05) for steers fed 4% tallow, probably due to greater triglyceride concentrations at the time of lipid dosing. In summary, few responses to abomasally infused choline were observed in either digestion or plasma metabolites.