Genetic variation of pregnancy rate (PR) using the number of opportunity intervals in US Holsteins was assessed by an ordinal censored threshold model assuming unknown voluntary waiting period (VWP). 46 180 reproductive records of days open (DO) or days to last service (DLS) and days to first service (DFS) from 29 725 cows were used. Thirty-eight percent of records were censored. Average DO and DLS were 128 d and 148 d for pregnant and censored records. Majority of the estimated 95% credible intervals for VWP covered their farmers reported VWP values. Posterior mean of heritability to number of opportunity interval after VWP (PR) was 0.05 with posterior standard deviation being 0.009.

Y. M Chang, O. Gonzalez-Recio, K. A Weigel, P. M Fricke

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.16, 2006
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