RUMEN FERMENTATION AND NUTRIENT FLOWS FOR COWS FED GRASS AND GRASS SUPPLEMENTED WITH MOLASSED BEET PULP PELLETS

An experiment was carried out to determine the effect of a grass diet and a concentrate supplement on rumen fermentation and nutrient flows to the duodenum. Perennial ryegrass was cut and fed indoors to eight r umen-and duodenum-cannulated Friesian cows with or without 3 kg/d of m olassed beet pulp in a randomized design experiment. The dry matter in take of grass was significantly lower for cows fed the concentrate sup plement (13.6 vs. 11.5 kg of dry matter/d), but total dry matter and o rganic matter (OM) intakes were similar for cows fed both diets. Cows fed the supplement had higher mean concentrations of total volatile fa tty acids (108 vs. 89 mmol/L) and a higher percentage of butyrate in t otal volatile fatty acids (13.5 vs. 11.6 mol/100 mel). There were no d ifferences between the diets in the flow of OM to the duodenum or in t he extent of OM digestion in the rumen. Flows of nonammonia N, microbi al N, and amino acids to the duodenum tended to be higher for cows fed the supplemented diet than for those fed ryegrass only. The efficienc y of microbial protein synthesis also tended to be higher for cows fed the supplemented diet (42 vs. 37.7 g/kg of OM apparently digested in the rumen and 28.2 vs. 26 g/kg of OM truly digested in the rumen). Ove rall, there were indications that the supplement caused better capture of N in the rumen and increased the efficiency of microbial protein s ynthesis.