Abstract.Atotal of 840 calvings and lactations were analysed in 340 Polish Holstein-Friesian cows in 2003–2006. The following reproductive traits of the cows were determined: calving interval, calving to conception interval, period of reproductive quiescence, remating interval and insemination index. These traits were analysed in terms of milk yield over a full lactation. Coefficients of correlation were also calculated between milk yield and reproductive parameters analysed. The reproductive parameters studied were significantly differentiated by the milk yield of cows. The calving interval increased from 369 days (milk yield <6000 kg) to 540 days (milk yield >14 000 kg). In the successive classes of milk yield, the calving to conception interval increased from 98 to 264 days, the period of reproductive quiescence increased from 68 to 117 days, and the remating interval increased from 30 to 147 days. The insemination index was the lowest (1.8) in the first class of milk yield and the highest (3.6) in the sixth class of milk yield. The coefficients of correlation between lactation yield and the reproductive parameters analysed were positive and highly significant. The highest coefficients of correlation (0.4xx) were found between milk yield and the calving and calving to conception intervals.

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