Xizang Agricultural and Animal Husbandry University, Xizang Agricultural and Animal Husbandry University, Xizang Agricultural and Animal Husbandry University, Xizang Agricultural and Animal Husbandry University, Xizang Agricultural and Animal Husbandry University, Xizang Agricultural and Animal Husbandry University, Xizang Agricultural and Animal Husbandry University, affiliation not provided to SSRN and affiliation not provided to SSRN