The influence of the season of parturition on milk performance in the Czech pied cattle

The data on 376 076 lactations of Czech Pied cattle were analysed and the p roduction of milk, milk protein, milk fat and percentage of milk protein an d fat were calculated. First (n = 166 739), second (rt = 117 071) and third (n = 92 269) lactations were included. Average production in the first lac tation was 3 642 (s = 807.3) kg of milk, 119.3 (s = 27.52) kg of protein? 3 .31 (s = 0.194) % of protein, 4.22 (s = 0.389) % of fat and 153.48 (s = 36. 64) kg of fat. Cows in their second lactation produced on average 4 106 (s = 911.7) kg of milk, 135.6 (s = 30.23) kg of protein, 3.34 (s = 0.192) % of protein, 4.24 (s = 0.419) % of fat and 173.68 (s = 41.86) kg of fat. Avera ge production in the third lactation was 4 328 (s = 954.7) kg of milk, 142. 3 (s = 32.9) kg of protein, 3.31 (s = 0.187) % of protein, 4.23 (s = 0.426) % of fat and 184.78 (s = 44.37) kg of fat. The average age at first calvin g was 28 months and 22 days (s = 3 months and 9 days). The month of calving had a significant effect on milk production per lactation. The maximum pro duction of milk was found in cows which calved in winter months (December-M arch), the lowest production was found in cows which calved form June to Se ptember. The milk production of cows which calved in these two groups of mo nths was similar, the most of the differences was not statistically signifi cant. A similar trend was found in the second and third lactations. However , the maximum and minimum production per lactation was reached by cows whic h calved in slightly different groups of months. Therefore it is suggested that months should be grouped into seasons (for the purpose of estimation o f breeding values) on different basis for cows in the first lactation and f or cows in the second and third lactation.