For genetic evaluation and contemporary group ratios, weaning weights are standardized
to a calf age of 205 days and a mature dam equivalent. In the past, calves outside
the range of 160 to 280 days of age were excluded from American Angus Association
National Cattle Evaluation procedures. As a result, the calves weaned earlier than
160 days did not receive 205-day weights or contribute to genetic predictions.
Use of these records for genetic prediction requires a new approach to the traditional
205-day weight. The traditional 205-day age adjustment tended to overestimate the
adjusted weights on younger calves and underestimate the values on older calves.
To improve this process, breed-specific nonlinear equations were developed to adjust
calf weights to a common age. This allows fair, age-equivalent comparisons among
calves weaned between 120-280 days. This new adjustment formula is applied to weaning
weights processed after June 8, 2003.
The enhanced 205-day adjustment procedure permits acceptance of data into the genetic
evaluation that had been previously excluded by the calf age window. Lowering the
minimum acceptable weaning age to 120 days provides breeders flexibility in weaning
dates, along with allowing younger calves to remain in their respective contemporary
groups for National Cattle Evaluation.
American Angus Association®
3201 Frederick Ave. St. Joseph, MO 64506
Contact us: phone 816.383.5100 fax 816.233.9703
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