Analysis of the course of calving in Polish Holstein-Friesian cows serviced with the semen of Belgian Blue bulls

The aim of the study was to analyse the course of calving in Polish Holstein-Friesian cows serviced with the semen of Belgian Blue bulls. Data for the researches was provided by the results of the calving of 155 cows inseminated with the semen of Belgian Blue bulls. The data covered both calving difficulties as well as stillborn calves. The cases of difficult deliveries in commercial crossing were comparable with those occurring in pure black and white herds. Out of 155 monitored calvings, 132 (85.16%) were classified as "normal", 16 (10.32%) as "difficult" and 5 (3.22%) as "very difficult". There were also 2 caesarians. The calving course was influenced by the cow's BCS (body condition score), as well as by the calf's sex and body condition at birth. Body condition score (BCS) had a statistically significant influence (p <= 0.05) on the calving course. The highest ratio (9.5%) of difficult deliveries was noted in cows whose BCS had been described as "very good". The higher ratio of difficult calvings was observed in the case of bull calves. The ratio of difficult deliveries increased along with the calf's body weight at birth. In conclusion, the occurrence of dystocia when the semen of Belgian Blue bulls was used was similar to that observed in pure Polish Holstein-Friesian herds.