In the present paper the heritabilities and repeatabilities of difficult calvings in Black and White cows are estimated. The highest heritability (0,135) was found for the first calving and a slightly lower one for the second and third. The lowest (0,058) heritability was noted for the fourth and later perities. This result indicates the possibility of an effective selection of bulls for the direct effect on calving difficulty.
The purpose of the present paper was to estimate the frequencies of difficult calvings and calf mortality in Black and White and Red and White cattle. Calvings were recorded for 24,045 Black and White and 5,353 Red and White cows. Dystocia was more frequent in Red and White heifers (15.5%) than in Black and White heifers (9.2%). In cows the frequency of difficult calvings decreased by half. The highest calf mortality was found in Black and White heifers (11.4%) and Red and White heifers (9.6%). In older cows the mortality was much lower.