Animal Science Department


Date of this Version

January 1981


Published in J Dairy Sci 1981, 64:484-490. Copyright © 1981 The American Dairy Science Association. Used by permission.


The standard of comparison for dairy production records is the 305-day lactation, and 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 first lactations of 73,724 daughters of 1,362 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 two lengths (60 to 80 days and 130 to 160 days) on the same daughters were extended by three methods, and sire proofs were computed from these six sets of extended records. Correlations between sire proofs with complete records only and sire proofs with only extended incomplete records were .93 or .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 (.66 to .81 for milk proofs), as expected, when the length of the part record was between 60 and 80 days.