Influences of dam on calving difficulty and early calf mortality.

Influence of dam on calving difficulty and calf mortality was evaluated for repeatability of past performance and daughter-dam relationships. Repeatability for calving performance at first with second parity was .16 and for consecutive calvings at second and later parities .10. Repeatability for calf mortality from first to second parity was .02 and for consecutive calving at second and later parities .02. A small but real tendency existed to repeat prior calving performance but not calf livability . Repeatabilities for dystocia were approximately double heritability. Difficulty scores should not be combined because of loss of predictive value of future performance. Relationship of calving difficulty to calf mortality varied depending on whether the calf was born dead or died within 48 h postpartum. Livability scores for those classes should not be combined when calf mortality-calving difficulty interactions are investigated. The hypothesis of negative direct maternal correlation for dystocia resulting from small calves born with ease becoming small cows that have increased dystocia was not disproven for first and second parities. Cows with above average difficulty produced daughters with above average difficulty, and heritability of dystocia as a trait of the dam was .24 by regression of daughter on dam.