A national fertility evaluation was developed based on pregnancy rate, which measures the percentage of nonpregnant cows becoming pregnant within each 21-d opportunity period. Data for evaluation are days open, which are calculated as date pregnant minus previous calving date. Date pregnant is determined from last reported breeding or from subsequent calving minus expected gestation length. Success or failure of last breeding can be confirmed by veterinary diagnosis or a report that the cow was sold because of infertility. Data are adjusted for parity and calving season within geographic region and time period and evaluated. Fertility records are considered complete at 250 d in milk, and lower and upper limits of 50 and 250 d are applied to days open. For calculation of genetic evaluations, days open are converted to pregnancy rate by the linear formula pregnancy rate = 0.25 (233 - days open). Evaluations are expressed as predicted transmitting ability for daughter pregnancy rate, and calculation is done with an animal model. Genetic correlations among several fertility measures and other evaluated traits were estimated from 3 large data sets. Correlation with days open was less for nonreturn rate than for days to first breeding, probably because nonreturn rate had lower heritability. Cow fertility was negatively correlated with yield but is a major component of longevity. Thus, recent selection for longevity may have slowed the long-term decline in fertility. Direct selection for fertility could halt or reverse the decline.

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Replacing cows on a dairy is a major cost of operation. There is a need for the industry to adopt a more standardized approach to reporting the rate at which cows exit from the dairy, and to reporting the reasons why cows are replaced and their destination as they exit the dairy. Herd turnover rate is recommended as the preferred term for characterizing the cows exiting a dairy, in preference to herd replacement rate, culling rate, or percent exiting, all of which have served as synonyms. Herd turnover rate should be calculated as the number of cows that exit in a defined period divided by the animal time at risk for the population being characterized. The terms voluntary and involuntary culling suffer from problems of definition and their use should be discouraged. Destination should be recorded for all cows that exit the dairy and opportunities to record one or more reasons for exiting should be provided by management systems. Comparing reported reasons between dairies requires considerable caution because of differences in case definitions and recording methods. Relying upon culling records to monitor disease has been and will always be an ineffective management strategy. Dairies are encouraged to record and monitor disease events and reproductive performance and use this information as the basis for management efforts aimed at reducing the need to replace cows.