Influence of the physical form of a barley grain and barley straw diet on nitrogen metabolism in sheep

Abstract

1) Two wether sheep fitted with ruminal and duodenal re-entrant cannulas were used to study the influence of the physical form of a barley grain and barley straw diet and intraruminal addition of ammonium salts (mainly acetate) on digestibility of dietary constituents, the flow of digesta to the duodenum and the composition of digesta from the rumen and duodenum.(2). Grinding and pelleting of the diet depressed the digestibility of crude fibre and increased that of the nitrogen-free extract and addition of ammonium salts increased the digestibility of crude fibre. The effects of the physical form of the diet on the composition of the short-chain fatty acids of rumen liquor were not consistent and the addition of ammonium salts produced changes over and above those attributable to the small amounts of acids in the mixture. The extreme values observed for the molar proportion of propionic acid were 12-3 and 38-1% and the corresponding values for w-butyric acid were 28-1 and 9-0%.(3). Variations in the flow of nitrogenous materials to the duodenum were related more to the pattern of fermentation established in the rumen than to the experimental treatments. There was a highly significant relationship between the molar proportion of propionic acid and the abomasal output of nitrogen and also the abomasal output of a-e-diaminopimelic acid and a-linked glucose polymers. The amino acid composition of duodenal digesta differed from that of the diet-in particular the proportion of glutamic acid was decreased and the proportions of aspartic acid, alanine, lysine and histidine were increased-but differences in composition between treatments and between animals were small.(4). The faecal output of nitrogen differed little between animals and between treatments, but nitrogen retention was significantly increased during the intraruminal infusion of ammonium salts.Alteration of the physical form of a diet, by grinding and pelleting, is known to influence the digestion of food materials in the rumen, and effects can be especially marked with diets containing a high proportion of concentrated foods. There are reports of effects on the composition of short-chain fatty acids in rumen liquor and the rate of passage of food particles (for references, see Moore, 1964;Shaw, 1961),

Interactions between dietary carbohydrate and nitrogen and digestion in sheep

“…It has been suggested that 'propionate' fermentations are more effective for rumen nitrogen use than 'butyrate' fermentations (Jackson, Rook & Towers, 1971). We found no consistent evidence for this.…”

A comparison of sources of supplementary nitrogen for young cattle receiving fibre-rich diets

“…The changes noted were small in size and all values fell within the range reported by Smith, Broster & Siviter (1980). A link has been suggested between the concentration of propionate and the amount of microbial protein reaching the duodenum (Burt, 1971;Ishaque, Thomas & Rook, 1971;Jackson, Rook & Towers, 1971). Concentrations of rumen NH 3 -N were also increased by the supplements, urea resulting in the highest peak values and the fastest rate of decline between meals (Smith, 1978).…”

Studies on the adaptation of the rumen to the hydrolysis of biuret in cattle

“…The practical importance of this finding is that feeding a carbohydrate source for a short period when biuret is first introduced into the diet, would be expected to stimulate a faster microbial activity or adaptation rate to biuret. Results reported by Ishaque, Thomas & Rook (1971) and Jackson, Rook & Towers (1971) suggest that on grain-based diets, the efficiency of rumen microbial protein synthesis is greater, which would indicate an increase in the microbial population.…”