Rumen Metabolism in Sheep as Influenced by Interactions among the Ration's Energy Content, Physical Form and Buffers

The influence of rumen metabolism of interactions among the rations' energy content, physical form and buffers were studied in a randomized complete block trial with rumen fistulated sheep. The productions of total VFA and acetate, propionate and butyrate were estimated at various times after feeding by in vitro techniques and presented on a gram DM basis. Rumen dry matter and pH were also determined on the rumen samples. The concentrations of the total and individual VFA responded to the various factors under study. However, there were few differences in the production of these acids. Acetate production was not affected by the source of energy. There was a greater production of propionate and butyrate with the high than low energy diets. Sodium bicarbonate increased acetate, propionate and butyrate production. Propionate production was the only acid significantly influenced by hours after feeding with the greatest rate of production occurring at 1 hour. The concentration of the total and individual VFA concentration in the rumen had little or no significance as a criteria of evaluating rumen metabolism of feeds as affected by the factors studied. The lambs fed the concentrate energy source had a more severe parakeratotic rumen than lambs fed the roughage energy source. The pelleted rations were more detrimental than the milled rations. Sodium bicarbonate alleviated the severity of rumen parakeratosis for both levels of energy and physical forms. It appears that rumen buffering capacity in relation to energy intake and rumen metabolism is a major contributing factor towards predisposition of parakeratosis.