Buffering capacities of rumen and caecal digesta from sheep

Abstract

Pruc. Aust. Soc. Anim. Prod. 1996 Vol. 21 BUFFERING CAPACITIES OF RUMEN AND CAECAL DIGESTA FROM SHEEP Z. DINGAB, J.B. ROWEA, I.R. GODWINB and Y. XU AB * Dept of Animal Science, University of New England, Armidale, N.S.W. 235 1 * Dept of Physiology, University of New England, Armidale, N.S.W. 235 1 Acidosis as a result of rapid fermentation of starch or sugars can occur in the rumen or hind gut (Godfrey et al. 1992). Saliva contains both bicarbonate and phosphate which provide important sources of buffer in the rumen. However, there is no similar supply of buffer in the caecum. The aim of these experiments was to investigate the buffering capacities of rumen and caecal digesta taken from Merino sheep weighing between 30 to 45 kg. Sheep on different diets were used in 3 experiments. In experiment 1, six wethers were individually penned and fed oat chaff 900 g/day, hourly for 4 weeks before the experiment. In experiment 2, three wethers were fed oat chaff 900 g/day for 2 weeks at hourly intervals before receiving intra-ruminal infusions of glucose, lactic acid or acetic acid in order to induce acidosis (pH < 5.2) in the rumen. The samples of rumen and caecal digesta were taken for the experiment 48 hours after acidosis was induced. In experiment 3, five ewes grazing green pasture were used. Following euthanasia, samples of rumen and caecal digesta were taken to determine buffering capacities. The buffering capacity of the digesta was determined by titration with 1 molL lactic acid, acetic acid or HCl, respectively, and all titrations were carried out in a hot room (37�C). The results are summarized in table 1. The buffering capacity is defined as the amount of acid required to change pH of digesta by 1 unit and calculated for change from pH 6.5 to 6.0. Table 1. Buffering capacities (mean values SEM) of rumen and caecal digesta ofsheep at 37�C and pH 6.5-6.0 (mol acid/ml digesta/ unit pH change) It is very interesting that, despite there being no input of saliva into the caecum, the buffering capacity of caecal digesta was higher than that for the rumen digesta. This could be a result of the higher dry matter content of the caecal digesta and the greater concentration of buffering agents. The buffering capacities of rumen and caecal digesta may vary depending on feed and water intake before slaughter. GODFREY, S.I., BOYCE, M.D., ROWE, J.B. and SPEIJERS, E.J. (1992). Amt. J. Agric. Res. 44:1093101. 343