Voluntary intake and kinetics of degradation and passage of unsupplemented and supplemented pastures from semiarid lands in grazing goats and sheep

Interspecies differences in voluntary intake and fractional rates of passage and degradation of digesta in goats and sheep grazing on semiarid lands in the south-east of Spain were studied following a 2 (animal species) X 3 (period of the year, i.e., phenological state) X 3 (feed supplementation) factorial design. The animals were on a semi-extensive management system and were fed, from early spring to late summer, pasture unsupplemented or supplemented (88 g DM/animal/d) with barley grain or with barley grain plus urea. The voluntary intake met the energy (ME) requirements for maintenance in goats but not in sheep. The voluntary intake of organic matter of pasture (POMI) was significantly (P<0.05) affected by the phenological state of the pasture and significantly reduced by supplementation (P<0.05). The total organic matter intake (TOMI) remained unchanged. Goats had significantly (P<0.05) faster fractional rates of passage of digesta from the rumen than sheep. Neither the phenological state nor the supplementation affected the particle outflow rate. The fractional rate of degradation of both dry matter (DM) and crude protein (CP) seemed to be slightly higher in goats than in sheep, whereas it was unaffected by supplementation. Effective degradability (Ed) of DM both in goats and sheep decreased from early spring to late summer.