The relationship between calving difficulty and post partum disorders and their influence on milk production in the early lactation of dairy cows.

761 calvings have beem included in the study: 159 of which were from Bulgarian Black and White cows and 566 – from Bulgarian Brown multiparous cows. Cows have been reared on one and the same farm, tied, milked twice daily. The factors that influenced the occurrence of calving difficulties, metritis, postparturient paresis, ketosis and laminitis as well as the interrelationship among them and their influence on the average daily milk yield during the first month of lactation have been studied. The obesity of cows with body condition score (BCS) above 4 points prepartum resulted in higher live weight of newborn calves and a significantly increased risk of difficult calvings. The latter could result in risk of retained placenta. The principla causes for postparturient metritis were the problems at calving, the retained placenta and ketosis. The risk of postparturient ketosis increased in obese cows with BCS above 4 points. The low as well as the high BCS before calving increased the risk of postparturient paresis in cows. The diseases related to metabolic disorders - ketosis and postparturient paresis, increased the rsik of laminitis after calving. Calving difficulties and early metritis had no significant influence on the average daily milk yield during the first month of lactation. Metabolic disorders and laminitis caused a considerable decrease in the average daily milk yield of cows during the first month of lactation.