Contribution of Days Since Bred, Herd Average, and Sample-Day Production to Accuracy in Projecting Lactation Records

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Abstract
Holstein [cow] sample-day production records from the North Carolina [USA] processing center were used to evaluate several models for accuracy in projecting partial production records to 305 days. Production on the most recent sample day was the best single predictor of production from the end of the partial record to 305 days. Herd average increased accuracy for records of fewer than 125 days. Days since bred improved accuracy for records of more than 55 days. The remaining yield of first lactation was predicted with increased accuracy if the partial record production was used in addition to the other variables starting at 55 days. The following three conditions were considered: all information available, days since bred lacking and days since bred and last sample-day production lacking. An optimum system for each condition was assessed.