Effects of dietary carbohydrate composition on rumen fermentation, plasma hormone and metabolites in growing fattening bull

peer reviewedA finishing diet containing barley and sugarbeet pulp 500:200 or 200:500 g/kg was given to 12 bulls twice daily at 08.00 and 16.00 h. The high-pulp diet increased rumen acetic and butyric acids and decreased propionic acid compared with the high-barley diet. The diurnal patterns over a 24-h period of rumen pH, volatile fatty acids, glucose and ammonia were characterized by 2 cycles. The high-pulp induced more even fermentations as indicated by flatter curves with less extreme values than those produced by high-barley diet. Ammonia concentration was high before feeding and decreased subsequently during 4 to 6 h after the meal. No typical patterns were observed in plasma concentrations of glucose and alpha-amino nitrogen. Plasma urea concentration increased 2 h after feeding and dropped during the following 6 to 8 h. There were no effects of dietary carbohydrate composition on growth hormone concentration but plasma insulin was significantly reduced with the high-pulp diet. Furthermore, the insulin profile showed peaks after each meal with the high-barley diet but only after the afternoon feeding with the high-pulp diet