EN
The aim of the study was to examine the influence of twin pregnancy on the course of calving and the vitality of calves born after commercial crossing of Black-and-White cows with Piemontese bulls. The investigation covered the following: calving course (A) normal, easy without or with minor assistance, (B) heavy with personnel assistance needed, (C) complicated with vet assistance; calf vitality: (A) normal healthy, (B) weak, (C) born dead or died within 24 hours; and calf body weight at birth (kg). Twin pregnancies were shorter than the single ones by 2 days on the average. The longer pregnancy period increased the number of complicated calvings. Pregnancies finished with normal delivery were shorter by 3.4 days in case of single and by 3.7 days in case of twin pregnancies in comparison to ones finished with complications. Calves born dead or that died within 24 hours were delivered 3.5 days (single) and 4 days (twin) longer after the pregnancy in comparison to ones finished without any problems. In the case of twin pregnancies, 10.9% of the deliveries needed veterinary assistance; moreover, a lower percentage of easy calvings were noticed. As much as 20.3% of calves born after twin calving were dead or died before they had lived 24 hours. In the case of single pregnancies this percentage was only 0.9%. To summarize, it should be stated that in the case of twin pregnancies the ratio of difficult calvings increased, calf vitality was lower and their body weight at birth decreased. Longer pregnancy had a negative impact on calf vitality and increased its body weight at birth. Higher calf body weight at birth decreased its vitality.