In the tested cows, least square means for milk yield, protein and fat content (%) were - 8430.8 plus-minus 560.71; 3.17 plus-minus 0.0517 and 3.77 plus-minus 0.167 for the A1A1 genotype, 8434.9 plus-minus 222.80; 3.20 plus-minus 0.020 and 3.90 plus-minus 0.066 for the A1A2 genotype, and 7902.3 plus-minus 971.17; 3.28 plus-minus 0.089 and 3.90 plus-minus 0.288 for the A2A2 genotype.