farid moslemipur dep. animal science,gorgan university of agricultural sciences and natural resources, gorgan, iran noormohammad torbatinejad dep. animal science,gorgan university of agricultural sciences and natural resources, gorgan, iran homayun khazali dep. biology, shahid beheshti university,tehran, iran saeed hasani dep. animal science,gorgan university of agricultural sciences and natural resources, gorgan, iran taghi ghoorchi dep. animal science,gorgan university of agricultural sciences and natural resources, gorgan, iran

فرید مسلمی پور, تقی قورچی, نورمحمد تربتی نژاد, سعید حسنی,