British Cattle Veterinary Association

dairy cattle which have been selected principally for yield during the past 30 years. However this correlation is less than 1, and there is sufficient variation in the relationship for sires to be identified which are above average in both fertility and yield. The breeder can now identify these desirable sires, using the UK Fertility Index. In common with fertility indexes in use in other countries, the UK index depends on fertility information on individual cows recorded at the farm. The data recorded are open to management biases, and as a result typically have a low heritability.