The research were carried out in the herd with average annual number of 185 dairy cows in 2008 with average annual milk yield 8.009 kg. The animals were kept in a loose barn with deep litter system and were fed in TMR system. Statistical analysis considered the influ ence of first calving age, next calving, calving season, milk yield in standard lactation length and dry period length on fertility indices. It was found that the level of fertility indices was influenced by all analyzed factors. It should be emphasized that this influence was, however, not the same. Insemination index, length of interpregnancy and intercalving period were most influenced by length of complete lactation and previous dry period length. Decreasing of fertility indices with an increase above 8.000 kg of milk yield in standard lactation were observed. It suggests, that an increase of milk yield to 8.000 kg would not significantly decrease reproduction efficiency.

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