Factors limiting the intake of feed by sheep. IV. The intake and digestion of mature ryegrass

Abstract

Intake and digestion studies were conducted with sheep fed on ryegrass hay containing 6% crude protein and having an organic matter digestibility of 58%. The intake of ryegrass was little affected when additional protein was provided both as a dietary supplement and as an infusion per abomasum. When supplements containing adequate amounts of protein and minerals were given, the intake of the hay was still comparatively low at 780 g organic matter per day. Grinding and pelleting the diet of hay + supplements permitted a higher feed intake. It was concluded that feed intake was limited by the resistance of the organic matter of the hay to removal from the rumen. Digestion studies were conducted at a level of feeding equal to approximately 90% of the ad libitum intake. The quantity of organic matter apparently digested in the stomach was equal to 60% of the organic matter digested in the alimentary tract; about 80% of the digestion of fibre took place in the stomach. There was a net daily gain of 7.5 g of nitrogen during the passage of digesta through the stomach, and part of this gain appeared to be due to the passage of endogenous nitrogen into the rumen. The apparent digestibility in the intestines of nitrogen that left the stomach in digesta was 73%; 1.6 g of nitrogen was apparently digested in the intestines per 100 g organic matter intake. Values of certain parameters relating to the movement of digesta through the stomach were similar to those previously recorded with a low quality cereal hay.