From Guidelines for Uniform Beef Improvement Programs by the Beef Improvement Federation (BIF)
Weaning weight. Weaning weights are used to evaluate differences in growth potential of calves and the milking ability of dams. In order to evaluate differences in weaning weights, individual calf records must be adjusted to a standard basis. It is recommended that weaning weights be standardized to 205 days of age and a mature age of dam basis. Weaning weights should be taken when a contemporary group of calves averages about 205 days of age. Adjusted weaning weights should be calculated for calves within an age range of 160 to 250 days of age. Records on calves weaned outside this range should be given a special management code and handled as a separate management group. They should not be adjusted for age of dam, because appropriate correction factors are not available.