Relationships Among Proofs for Survival, Culling, and Yields in First and Later Lactations

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Abstract
Sire evaluations for survival to 84 mo and age at last record from unregistered cattle were regressed on combinations of the following: BLUP summaries for percent culled in first lactation (from unregistered cattle) and PD mild from all, first, later, and later minus first lactations. Correlations between sire summaries for survival and the other traits were all favorable. Of the yield variables, PD from later lactations had the largest correlations with the summaries for survival. Predicted Difference based on first lactations had a low correlation with survival to 84 mo. Partial regressions indicated that PD for yield in first lactation was of little value to predict survival rates after percent culled. Predicted Difference for yield in later lactations and the difference in PD (later minus first) were significant when fitted after percent culled. The difference in PD was significant when fitted along with percent culled and PD milk from all lactations. Low early culling, high later lactations, and large increases in yield from first to later lactations were associated with greater survival rates to older ages. Higher yields in later lactations may be associated with cows that are able to maintain their health.