Metabolic studies on daily and weekly feeding of ruminants given all-wheat diets. 2. Concentrations of metabolites in blood and ruminal fluid

Abstract

The respective effects of giving sheep 300 g whole wheat once each day or 2100 g once each week on the products of digestion in the rumen and the concentrations of several metabolites in the blood have been studied. Some studies were also made on cattle offered either daily or weekly rations of whole wheat. Related to the differing patterns of feed consumption on the two regimens, the fluctuations in ruminal fluid parameters were much greater for sheep and cattle fed weekly than on the daily feeding regimens. In sheep the mean total volatile fatty acid concentration and pH in ruminal fluid were similar on the two regimens, while when cattle were fed weekly, the volatile fatty acid concentration was higher (not significantly) and the pH lower. Weekly-fed sheep had lower rumen ammonia and branched-chain volatile fatty acid concentrations, whereas in cattle there was no difference between regimens. The rumen concentration of valeric acid was higher in both sheep and cattle fed weekly. In daily-fed sheep there was no diurnal variation in the concentrations of blood metabolites with the exception of free fatty acids. In contrast in weekly-fed sheep, the large changes in concentration of D(-)-glucose, L(+)-lactate, 3-hydroxybutyrate, urea and free fatty acids indicated phases of protein synthesis and lipogenesis following feeding, and protein and lipid mobilization at the end of the feeding cycle. It was concluded that in weekly-fed sheep there was a shift in the site of digestion from the rumen to the small intestine, but in cattle there was no evidence that the sites of digestion differed substantially between the two regimens.