NATIVE LOWLAND HAY IN PELLETED AND NON-PELLETED RATIONS FOR SHEEP: III. EFFECTS ON PRODUCTION OF VOLATILE FATTY ACIDS IN THE RUMEN
Concentrations and proportions of volatile fatty acids (VFA) were determined chromatographically in samples of rumen contents from 27 lambs and 5 mature wethers fed a control ration of alfalfa and barley or non-pelleted and pelleted test rations containing 45, 60 or 90 per cent of poor quality lowland hay in the case of lambs, and 60 or 90 per cent of test hay in the case of wethers.When the rations were fed in pelleted form, concentrations of VFA increased in rumen contents from lambs receiving 45 and 60, but not 90 per cent levels of lowland hay. In the case of the wethers, pelleting resulted in higher levels of the acids in rumen contents when either 60 or 90 per cent of test hay was fed. Pelleting had no effect on the proportions of VFA in the rumen fluid. Differences in concentration of VFA in rumen fluid were not of sufficient magnitude to account for more than a small fraction of the differences observed in feed consumption and rate and efficiency of gain of the fattening lambs fed the pelleted vs. non-pelleted rations.Concentrations of VFA were lower in rumen fluid from animals fed lowland hay than in that from animals fed the alfalfa-barley ration. As the level of lowland hay in the rations was increased the proportion of acetic acid increased, and the proportions of propionic and/or butyric acids decreased.