Nutritional studies with sheep fed conserved ryegrass. 1. Silage and dried grass offered ad libitum without supplements

Abstract

SummarySilage, dried-grass wafers and dried-grass pellets all prepared from a single crop of perennial ryegrass were given ad libitum as sole diets to six rumen-fistulated wether sheep.Feed intake, intake of digestible nutrients and the concentration of volatile fatty acids (VTA) in the rumen were lowest with silage, highest with pellets and intermediate with wafers. Conversely, digestibility, eating and ruminating time per kg D.M. consumed, rumen pH, the rate of D.M. and cellulose digestion in the rumen and the mean retention time of digesta in the alimentary tract were highest for silage, intermediate for wafers and lowest for pellets. The pattern of rumen fermentation differed significantly between silage and the dried-grass treatments. The rumen fluid contained higher proportions of acetic, iso-butyric, n-valeric and iso-valeric acids, but lower proportions of propionic and n-butyric acids with silage than with dried grass. Differences in rumen. VFA between the two forms of dried grass were small. Nitrogen retention was lowest for the silage treatment and this was associated with a high concentration of ammonia in the rumen.Low nitrogen status with silage could have limited voluntary intake, whereas the difference in intake between the wafer and pellet treatments probably arose from differences in the retention time of digesta in the alimentary tract.