THE ADDITION OF BUFFERS TO RUMINANT RATIONS: IV. THE EFFECT OF ADDITIONS OF SODIUM BICARBONATE, SODIUM PROPIONATE, LIMESTONE AND COD LIVER OIL ON INTRA-RUMEN ENVIRONMENT

Abstract

Two experiments with fistulated steers were designed to study the effects of adding 5.7 per cent sodium bicarbonate, 5.7 per cent ground limestone, and 5.7 per cent sodium bicarbonate plus either 3.6 per cent sodium propionate or 60 milliliters per day of cod liver oil to an all-concentrate basal ration composed of barley, oats, linseed oil meal, molasses, minerals and vitamins A and D2. The effects of using rolled or ground grains were also studied. All of the buffered rations, except that containing limestone, resulted in a higher rumen pH and buffering capacity than did the basal ration. The buffers had little effect on the total concentration but did result in changes in the molar proportions of the VFA in rumen fluid. In both experiments, the buffered rations, except that containing limestone, gave a lower molar per cent of acetic acid than did the basal ration. The addition of either cod liver oil or sodium propionate to the sodium bicarbonate ration resulted in a higher molar per cent of the propionic acid than with the basal ration. The butyric acid concentration was lower for the ration containing cod liver oil than for either the basal or sodium bicarbonate rations. Rolled grains in the basal ration gave less extreme results than did ground grains; however, the differences were not significant.Samples taken at 3, 5, 8 and 16 hours after feeding showed marked diurnal variations in all criteria studied, except the proportion of acetic acid. Values obtained at 3 and 5 hours after feeding showed little change but thereafter there was a decrease in concentration of total VFA and the proportion of propionic acid and an increase in pH, buffering capacity and the proportions of butyric and the higher acids. Interactions between the rations and times of sampling show that the buffers are most effective in modifying the intra-rumen environment shortly after feeding but this effect had partly disappeared by 5 hours after feeding.