The influence of days carried calf and dry period on milk and fat production in Tennessee DHIA herds

A number of items influence production records of dairy cows. Most dairy farmers recognize some of these, while many are generally overlooked. Items usually accepted as influencing production records are: age, body weight, frequency of milking, quality and amount of feed, general care and management, and length of lactation. Other items, affecting production, that are often given little attention are: the length of dry period, the number of days open during lactation, and calving interval. Conversion factors are available and in common use for age and milking frequency. Factors have been devised to adjust for the influence of days carried calf, but have not been widely accepted. With the growth of artificial insemination the problem of sire selection committees has been compounded. They have a tremendous responsibility to dairy cattle owners since they are making selection for all stud patrons. As sire selection is so hazardous, it is very important to account for all possible variables which may influence production records in order to improve the accuracy of selection procedure. Owners have the same problem in selecting foundation or replacement animals. However when considered on a herd basis, individual female selection will not exert nearly the influence on total potential improvement as male selection. The purpose of this study is to attempt to evaluate the importance of dry periods, and days carried calf as they influence production in DHIA herds in Tennessee.