Abstract: Genetic variation of three microsatellite loci BMS2258, SOD1, and BM723, which were closely correlated with GSH-Px, SOD, and Na⁺/K⁺-ATPase genes, was analyzed in 130 Holstein cows by PCR and nondenaturing polyacrylamide gel-electrophoresis. Polymorphic information content, effective number of alleles and heterozygosity of these microsatellite loci were determined. Relationships of the three microsatellite loci with enzyme activities and daily milk yields in Holstein cows were analyzed by least squares linear model. The results showed significant correlations of the three microsatellite loci with their corresponding enzyme activities and daily milk yield in summer and fall (P<0.05). The least square means of GSH-Px activities and daily milk yields for BMS2258 (182 bp/164 bp), SOD activities for SOD1 (148 bp/148 bp), and daily milk yields for SOD1 (148 bp/146 bp), Na⁺/K⁺-ATPase activities and daily milk yields for BM723 (161 bp/111 bp) were relatively higher. These genotypes were the most favorable genotypes for enzyme activity and daily milk yields in summer and fall, which could be references for marker assisted selection in heat resistance traits in dairy cattle.

Key words: cow, GSH-Px, SOD, Na⁺/K⁺-ATPase, daily milk yield, microsatellite locus