Study On The Limiting Nutritional Factors Of Grazing Sheep In Different Grazing Periods And Optimization Supplementary Feeding In Winter

Dry matter intake, pasture botanical composition and pasture DM digestibility on grazing sheep were measured in three different periods of pasture in young pasture, growing pasture and perishing pasture using alkane technique in Siziwangqi of Inner Mongolia, where stocking rate were 1.82 sheep / hm2/half year and 2.71 sheep / hm2/half year. The dynamic changes of pasture GI were measured in different periods of pasture under two grazing intensity. Based on above study, the major limiting nutritional factors of the region were investigated by the monitor technique of nutrition in different periods of pasture under two grazing intensity. Based on the major limiting nutritional factors, an optimum supplemental feed formula of grazing sheep was selected by GI value and the maximum of multiple-factors associative effects index (MFAEI), and the effects were validated by the supplemental experiment. The results showed: in different periods of pasture, under medium grazing intensity DM intake were 1.77±0.11kg/d, 1.71±0.03kg/d and 1.14±0.14kg/d respectively; under high grazing intensity DM intake were 1.82±0.06kg/d,1.52±0.01kg/d and 1.07±0.03kg/d respectively (p>0.05). And the pasture GI value were 5.18MJ, 2.99MJ, 0.90MJ and 5.30MJ, 2.55MJ, 0.85 MJ respectively (p<0.05). Following the changes of pasture growing periods, the nutrition of pasture decreased gradually. The pH value, NH3-N concentrations, VFAs concentrations in rumen liquid indicated CP and ME of young pasture and growing pasture could meet the need of sheep under two grazing intensity, but the CP and ME of perishing pasture were scarce seriously and inefficiently,which were major limiting nutritional factors. Considering the limiting nutritional factors, the supplemental diets of grazing sheep were designed,then an optimum supplemental feed formula of grazing sheep was selected. Compared with non-optimum group and control group, the body weight of grazing sheep which were fed optimum supplemental diets increased by 23.46%and 180%(p<0.05) respectively;And the economic profit increased by 45.63% and 113% (p<0.05) respectively; simultaneity the index of rumen liquid also improve significantly.