Studies on effects of different grazing intensity on productivity of Tan sheep

Five treatments(0.45,0.6,0.75,1.05,1.5 head/hm~2) and 3 plots under 42d-cycle rotational grazing system were designed to test the effects of different grazing intensity on Tan sheep productivity in Sidunzi,Yanchi county of NingXia,from May to November in 2003.The results showed that: 1) Feed intake of Tan sheep decreased as grazing intensity went up.Under the same grazing intensity,feed intake increased firstly,and then decreased as the time went by.2) The live weight of Tan sheep showed increasing tendency under different grazing intensity,but differentiated from October 2.Compared with those under higher grazing intensity,the sheep in light grazing intensity gained more live weight.3) There were negative correlation between live weight gain per sheep and grazing intensity and positive correlation between live weight gain per hectare and grazing intensity.4) With the increasing grazing intensity,feed conversion increased first,and then decreased.Under the same grazing intensity,feed conversion gave similar trend as grazing time prolonged.5) Under higher grazing intensity than 0.75 head/hm~2,the barren rate of Tan sheep increased,lambing percentage dropped and pregnancy postponed.6) As a result,the appropriate grazing intensity in this type rangeland could not exceed 0.75 head/hm~2.