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 p assage and degradation of digesta in goats and sheep grazing on semiar id 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-extensi ve management system and were fed, from early spring to late summer, p asture unsupplemented or supplemented (88 g DM/animal/d) with barley g rain or with barley grain plus urea. The voluntary intake met the ener gy (ME) requirements for maintenance in goats but not in sheep. The vo luntary intake of organic matter of pasture (POMI) was significantly ( P<0.05) affected by the phenological state of the pasture and signific antly reduced by supplementation (P<0.05). The total organic matter in take (TOMI) remained unchanged. Goats had significantly (P<0.05) faste r fractional rates of passage of digesta from the rumen than sheep. Ne ither the phenological state nor the supplementation affected the part icle outflow rate. The fractional rate of degradation of both dry matt er (DM) and crude protein (CP) seemed to be slightly higher in goats t han 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.