GENOTYPE × SEASON × METHOD INTERACTION IN EVALUATING DAIRY SIRES FROM PROGENY RECORDS

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Abstract
Correlations between transmitting-ability estimates made from records on daughters of the same sires in different seasons are presented. The estimates were made from specifications for different contemporary comparison and herd mate methods applied to the same total amount of data. The lowest correlations were those with the contemporary comparison procedure and no age correction. Age correction did not significantly increase the correlations when only first lactations were used. The standard herd mate comparison was superior to the contemporary comparison, but the use of all herd mates only slightly improved the correlation over those obtained using only second- and third-lactation herd mates. A new herd mate procedure, based on predicting first lactation performance from herd production and age, gave the largest correlations and thus minimized the genotype × season-of-freshening interaction.

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