Double insemination of cows during one oestrus

Data on insemination and reinsemination were collected from 1 643 Black and White (BW) cows with varied share of Holstein–Friesian (HF) genes, which belonged to the active population managed in five large–scale production farms in the Kujawsko–Pomorskie Province, Poland. A total number of 351 repeated inseminations were recorded, which amounted to 7.71% of all inseminations. The rates of non–return to oestrus after reinseminations were by 2.05% better in relation to single inseminations, however, an economical analysis led to a conclusion that double insemination does not produce economical benefits and can only be recommended in specific cases, e.g. with prolonged oestrus. Highly significant effect on non–return rates after inseminating once or twice was demonstrated for the factors of HF genes share, farm, milk yield, age at first calving, subsequent calving, and season of insemination.