TY JOUR TI GENE OF SOMATOTROPIN CASCADE POLYMORPHISMS, ASSOCIATED WITH BEEF PRODUCTIVITY OF KAZAKH WHITE-HEADED BREED COWS KW genes KW polymorphism KW marker KW cascade KW productivity KW breed KW somatotropic KW beef JO Bulletin Samara State Agricultural Academy AU Beishova, I.S. PY 2018 IS 3 PB Samara State Agrarian University