Prediction of Son's Modified Contemporary Comparison from Pedigree Information

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Abstract
Son''s modified contemporary comparison predicted differences and modified contemporary deviations based on daughters'' 1st lactations only and on all lactations were predicted for milk and fat yield and fat percent from pedigree information. Pedigree records included predicted differences and modified contemporary deviations for male relatives and modified contemporary deviations and cow index on 1st available records for female relatives. For a son''s dam, 1st 2 and 1st 3 available records were also used. Models were chosen by a stepwise procedure with stopping when there was a change in the multiple correlation coefficient squared of < 1%. Minimum repeatabilities of 40 and 70% for sons were required also to form 2 data sets. Models for milk and fat included sire''s and maternal grandsire''s predicted differences and dam''s cow index. Models for fat also included the modified contemporary deviation for the maternal grandsire. For fat percent, sire''s predicted difference or modified contemporary deviation and dam''s cow index were important. Multiple correlation coefficients ranged from .32 for fat percent and .31 for milk to .24 for fat. Two-variable models suggested that for milk and fat, maternal grandsire was more important than dam; dam was more important for fat percent. The dam''s cow index on 1st available record was more important for milk and fat, but dam''s cow index from 1st 3 available records was most important for fat percent. Results were similar for predicting son''s modified contemporary deviations. Closer prediction of son''s predicted differences to real predicted differences for yield of milk and fat were accomplished by placing more emphasis on the maternal grandsire, and for fat percent, by putting more emphasis on dam''s later records.
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