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The aim of this study was to determine the effect of the country of origin of the sire on the milk performance of primiparous Jersey cows kept under identical management conditions in Poland. Experimental cows were divided into four groups: daughters of bulls from the USA, Denmark, Canada and Poland. The effect of the paternal group on the milk performance of primiparous cows was estimated. A two-way contingency table was prepared to assess the association between the sire’s country of origin and peak lactation. To present the course of daily milk yield during 305-day lactation, linear graphs were plotted with linear trends depending on the origin of sires of primiparous cows. Daughters of Polish bulls, in comparison to the other genetic groups of primiparous cows, had by the lowest daily milk yields, as well as the lowest concentrations of protein and dry matter in their milk. Primiparous cows sired by bulls from Denmark had the highest daily milk yields and the lowest fat-to-protein ratios in their milk. Analysis of the effect of the origin of the sire on the milk performance of primiparous Jersey cows during 305-day lactation revealed significantly the lowest milk, protein and dry matter yield and the lowest content of protein in the milk for the daughters of Polish bulls. Primiparous cows from this group and the daughters of bulls from the USA had significantly the lowest fat yield and the lowest dry matter content in their milk. Daughters of Polish bulls in comparison to daughters of foreign bulls had a significantly higher concentration of lactose in their milk. The vast majority of primiparous Jersey cows sired by imported bulls reached peak daily milk yields from day 31 to day 60 of lactation. The lactation curve and the first-order trend for daily milk yields were most advantageous in primiparous cows sired by bulls from the USA and Canada. The use of semen from imported Jersey bulls in the Polish population of this cattle breed results in increased milk yields in primiparous cows sired by those bulls, as well as beneficial concentrations of milk constituents. The results of this study indicate that under Polish management conditions the use of semen from Danish bulls is preferable, although further research should be conducted to determine the lifetime productivity of cows and concentrations of milk constituents.

The effect of the country of origin of the sire on milk performance of primiparous Jersey cows