TAQI GROWTH-HORMONE GENE POLYMORPHISM AND MILK-PRODUCTION TRAITS IN HOLSTEIN-FRIESIAN CATTLE

The positive effect of administration of growth hormone (GH) on milk p roduction and its presence in selected dairy cattle lines of higher GH concentration prompted hormone gene using the enzyme TaqI and to inve stigate associations between this polymorphism and milk production tra its. Blood was sampled from 251 ltalian Holstein-Friesian cows. Three fragment bands, arbitrarily denoted A, B and E, of 6.2, 5.2 and 1.9 ki lobase (kb), respectively, were observed. Their combinations exhibited six patterns, AA, AB, ABE, AE, BB and BE with frequencies of 64.5, 24 .3, 2.4, 6.8, 1.4 and 0.4%, respectively. The statistical analysis was performed using linear mixed animal models. The results indicated an effect of the GH gene polymorphic TaqI restriction fragment on 305-day productions of milk, fat and protein; the low frequency pattern AE sh owed productions inferior to those for AA or AB patterns. Effect estim ates of AA, AB and AE were, respectively, 200 (s.e. 215), 218 (s.e. 26 7) and -910 (s.e. 380) kg for milk production, 7.75 (S.e. 7.98), 16.10 (s.e. 9.79) and -22.14 (s.e. 14.42) kg for fat production, and 6.78 ( s.e. 6.21), 8.57 (s.e. 7.58) and -20.74 (s.e. 11.14) kg for protein pr oduction. The average substitution effect of E were -891 (s.e. 278), - 26.56 (s.e. 10.16) and -24.50 (s.e. 9.43) kg for milk, fat and protein yields, respectively. In conclusion, these results suggest that the E fragment further designed and specific study.