Study On Sheep Grazing System Of Stipa Breviflora Desert Steppe

This paper, based on the sheep grazing ecosystem on Stipa breviflora desert steppe, investigated a number of parameters of both pasture and sheep, which included: characteristics of plant communities in different stocking rates, dynamics of the protective substance in plants, dynamics of the tantalum related to synthesis of the protective enzymes involved in the sheep of different breeds, activities of protective enzymes, changes of super-oxide dismutas, dynamics of the nutrition value of the plant communities, intake of the grazing sheep and composition of diets, nutritional limiting factors of grazing sheep and the compensatory schemes of the grazing sheep. The purpose of the study is to determine a rational stocking rate suitable for desert steppe, make supplemetry feeding schemes for grazing sheep and evaluate the anti-disease capacity of grazing sheep of different breeds.The results showed as follows.1. The compensatory growth of the plants was closely related with stocking rates on the desert steppe. When the stocking rate was below 1.213 sheep/hm2/year, the net productivity of the plant communities showed an equal-compensatory growth. Above the 1.213 sheep/hm2/year stocking rate, it showed a under-compensatory growth. The results suggested that rational stocking rates for this type of steppe was 1.027 sheep/hm2/year.2. Sheep grazing exerted a stress for plant growth. As the stocking rate increased, the contents of the SOD (superoxide dismutase), POD (peroxidase), malonaldehyde, proline and total sugar contents in the plants increased obviously.3. The nutritional elements such as zinc, copper, manganese participated in the synthesis of the protective enzymes. The body contents of such elements in the local Mongolian sheep breed were higher than those in the Dorset sheep.4. The activity of the SOD and the content of the super-oxide ion in Dorset sheep were higher than those in the local Mongolian sheep.5. The nutritional value of the natural steppe reached to the highest in the buding to early flowering period (June to July ),. Nutritional value decreased with the plant growth stage. In the grazing sheep diet, Artemisia frigida taking 79.7%, Cleistogens songorica taking 12.1%, and Convolvulus ammannii taking 7.3%.6. The crude protein content and metabolic energy of the steppe was devoid in the plant withering stage, which became the main limiting factor for grazing sheep. In...