Grazing management studies with Australian cashmere goats. 2. Effect of stocking rate on the liveweight gain of sheep and goats grazing an oats-rye grass pasture

摘要

Australian cashmere goats and Border Leicester x Merino sheep grazing an oats-rye grass pasture were used to study the effects of stocking rate (20, 40, 60 animals/ha) on growth, intestinal parasite burdens and haematology of the 2 species and on the persistence and productivity of the crop grazed. Goats and sheep were either grazed alone or together over a 12-week period to determine the interaction between the species. Liveweight gain decreased with both stocking rate and time on experiment. At the highest stocking rate all animals lost weight between weeks 9 and 12. During the first 9 weeks of grazing, sheep had significantly (P<0.05) higher liveweight gains than goats at all stocking rates; but the rate of decline in liveweight gain with increased stocking rate was similar in both species, whether they were grazed alone or together. Mean values for sheep were 161, 133 and 105 g/day, and for goats 101, 84 and 59 g/day at stocking rates of 20, 40 and 60 animals/ha. Under the same drenching regime, goats were more severely infested by intestinal parasites than sheep as indicated by significantly (P<0.05) higher concentrations of parasite eggs in faeces and lower packed cell volumes and haemoglobin concentrations in blood. Oats was the major contributor to green feed available at all stocking rates, although rye grass yields increased in the later stages of the trial, particularly in high stocking rate paddocks. At the end of the trial, high yields of oat stem remained in the paddocks grazed by goats and goats plus sheep, suggesting that sheep grazed both leaf and stem but goats selectively grazed oat leaf. The availability of green leaf (oat + rye grass) per animal was closely related to liveweight gain in any period, although these relationships were different for sheep and goats.