Grazing management studies with Australian cashmere goats. 1. Effect of stocking rate on the growth and fleece production of weaner goats grazing tropical pastures

摘要

Australian cashmere weaner goats were continuously grazed on either nitrogen (N) fertilised Pangola grass or mixed tropical legume-pangola grass pastures at 3 stocking rates (15, 30, 60 goats/ha). Grazing commenced in January and was terminated in May (18 weeks). Three parasite control treatments (Seponver, Avomec, Systemex) were superimposed on each treatment. Parasite egg counts, liveweight change, cashmere growth and changes in pasture components were measured. Intestinal parasite burdens were low (<400 eggs/g faeces) in all animals throughout the trial, and there were no significant effects of parasite control treatment on goat productivity. The liveweight gain of goats decreased with increasing stocking rate and time on pasture. Mean values for the liveweight change of goats on the legume-grass pasture were 66, 37 and 14 g/day at stocking rates of 15, 30 and 60 goats/ha, respectively. Comparable values for goats grazing N-fertilised pangola grass were 40, 39 and 23 g/day for stocking rates of 15, 30 and 60 goats/ha. Goats grazing the legume-grass pastures at the lowest stocking rate (15 goats/ha) had significantly higher liveweight gains than did goats on all other treatments. There were no significant effects of stocking rate, pasture type or worm control treatment on fleece growth in these goats. Mean values were 191 g, 39 g and 15.0 ¦m for fleece weight, cashmere weight and mean cashmere fibre diameter respectively. The major legume in the legume-grass pasture was siratro, with axillaris, greenleaf desmodium and cassia forming minor components (10-300 kg/dry matter (DM)/ha). During the first 6 weeks of grazing, all legume components increased under stocking rates of 15 and 30 goats/ha. Thereafter, there was a significant decline in siratro yield to less than 200 kg DMha at all stocking rates. During this same period, the yields of the other legumes generally increased, suggesting that at low stocking rates the goats preferred grass to legume, and when grass was limiting, siratro was the legume preferred over all others. Weed yields increased with time in all except the high stocking rate treatments. It was concluded that weaner goat growth can be maximised on tropical legume-pangola grass pastures when stocking rates and intestinal parasite burdens are low. Protein intake may be limiting growth on N-fertilised grass pastures.