GROWTH-HORMONE GENE POLYMORPHISM ASSOCIATED WITH SELECTION FOR MILK-FAT PRODUCTION IN LINES OF CATTLE

Fifty-eight calves of both sexes from lines of Red Danish dairy breed selected for high (n = 36) and low (n = 22) milk fat production, and 3 2 heifers from lines of Norwegian Red dairy breed selected for high (n = 16) and low (n = 16) milk fat yield were typed for two previously r eported restriction fragment length polymorphisms (RFLPs) in the growt h hormone gene. The RFLPs are consistent with: (1) an insertion(I)/del etion(D) of approximately 0.9kb in the 3'-region of the growth hormone gene and (2) a polymorphic MspI(+/-) site in the third intron. A trad itional RFLP procedure was used for typing the I/D polymorphism and a polymerase chain reaction (PCR) procedure was developed for typing the MspI polymorphism. Only the I-MspI(+) and D-MspI(-) haplotypes were f ound. In the Red Danish lines the frequency of D-MspI(-) haplotype was 0-28 in high line and 0.05 in low line calves, this difference was si gnificant (P < 0-01). The corresponding frequencies in the Norwegian R ed lines were 0.09 in the high line and 0.0 in the low line. Attempts to screen for RFLPs in the growth hormone receptor gene and in the ins ulin-like growth factor-I gene were unsuccessful.