Sire Evaluation by Only Extended Partial Milk and Fat Records

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Abstract
The standard of comparison for dairy production records is the 305 day lactation. Much research has been directed to estimating 305 day milk and fat records from incomplete or in-progress records. This study was to determine the effect of several methods of extending incomplete records on sire evaluation. Complete 305 day milk and fat records of 1st lactations of 73,724 daughters of 1362 artificial insemination Holstein sires processed at the New York Dairy Records Processing Laboratory were used to compute sire proofs for yield of milk and fat. Partial records of 2 lengths (60-80 days and 130-160 days) on the same daughters were extended by methods, and sire proofs were computed from these 6 sets of extended records. Correlations between sire proofs with complete records only and sire proofs with only extended incomplete records were 0.93 or 0.94 (for milk proofs) when the length of the part record was between 130 and 160 days, regardless of the method of extension. Correlations were less (0.66 to 0.81 for milk proofs), as expected, when the length of the part record was between 60 and 80 days.