One was collected the data about fertility results of 1 643 black-and-white cows (cb) with various gene share of Holstein-Friesian race. These cows by total number of calving – 4 707 kept in five byres in Kujawsko-Pomorskie Province, Poland. One analyzed the following traits of fertility: calving interval (OMW), pregnancy interval (OMC), pregnancy length, reproduction effectivity, insemination index, efficiency of first intervention. Interaction between genotype and farm as well as age on day of first calving, later calving and year season of calving on cow fertility was estimated. One ascertained that age on day of first calving and calving season in each genetic group didn’t influence significantly on cow fertility. Age of cows didn’t influence significantly on length of OMW and OMC instead one found significant influence on insemination index and efficiency of first intervention that were the best in primipara.

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