Lanzhou Institute of Animal Science and Veterinary Pharmaceutics,Chinese Academy of Agricultural Sciences, Lanzhou 730050, Gansu, P. R. China;
Lanzhou Institute of Animal Science and Veterinary Pharmaceutics,Chinese Academy of Agricultural Sciences, Lanzhou 730050, Gansu, P. R. China;
Lanzhou Institute of Animal Science and Veterinary Pharmaceutics,Chinese Academy of Agricultural Sciences, Lanzhou 730050, Gansu, P. R. China;