THE INTAKE OF GRASS AND RUSH (JUNCUS-EFFUSUS L) BY GOATS GRAZING RUSH-INFESTED GRASS PASTURE

The intakes of rush and grass by goats grazing rush-infested reseeded pasture (rush ground cover, 5.9%) were measured in three periods betwe en July and September in one year, using n-alkanes as dietary markers. Diet composition and intakes were measured at intertussock sward heig hts maintained at 3-4 cm and 5-6 cm and at an intertussock award heigh t maintained at 3-4 cm where the rushes had previously been grazed by goats to reduce rush green stem height to 0.75 of that of ungrazed tus socks. There was no effect of intertussock sward height or initial rus h green stem height on the dietary proportion (overall mean 0.51) or d ry matter (DM) intake of rush but there was an effect of period, which was related to changes in sward conditions over the experiment. Rush intake was positively related to the amount and accessibility of green rush stems and grass intake to intertussock sward height. Digestibili ty of DM of the diet, measured using n-alkanes, was high (overall mean 0.71), suggesting that the nutritive value of the rush is greater tha n previously estimated from in vitro digestibility measurements. Under these conditions, it appears that the goats select a mixed diet and t he results are consistent with animals selecting food items to maximiz e their rate of nutrient intake.