Rumen fermentation pattern in goats and sheep grazing pastures from semiarid Spanish lands unsupplemented or supplemented with barley grain or barley grain-urea

Abstract

An experiment following a 2 (animal species) ×3 (phenological state) ×3 (feed supplementation) factorial design was carried out with sheep and goats grazing on semiarid lands in the south-east of Spain. Animals consumed, from early spring to late summer, pasture alone or pasture supplemented with barley grain (88 g DM/an/d) or with barley grain plus 1% urea. The animals were on a semiextensive management system. Cell wall content was always slightly higher in the pasture selected by sheep. Significant ( P <0.05) interspecies differences in ruminal pH, ammonia nitrogen (NH 3-N) and total volatile fatty acids (VFA) concentrations and in molar proportions of acetic, n-butyric, isobutyric, iso-valeric and n-valeric acids were found in samples taken just before grazing. The contents of NH 3-N, total VFA, acetic, propionic and n-butyric acids at the highest microbial activity times were similar. The phenological state of the pasture had a significant effect ( P < 0.05) on rumen NH 3-N and total VFA contents. Supplementation with barley grain did not significantly change the rumen fermentation pattern, except for the n-valeric acid molar proportion which increased ( P<0.05) when barley was offered. This effect was not found when urea was added. It is concluded that there are differences in rumen fermentation pattern between sheep and goats. Those differences are influenced by the phenological state of the pasture but they are not affected by supplementation.