Analysis of non-return rate in Italian Holstein Friesian bulls

Until recently non-return rate 56 days (NR56) for Italian Holstein Friesian bulls had been published only for artificial-insemination (AI) organizations. Since December 2015, the information about sire fertility has been published also for the farmers. The objectives of this research were to assess the importance of information about the cow's age at insemination and editing of age of bulls for improving prediction of bull fertility. The intent was to revise the old model, even if NR56 is a phenotypic assessment of bull's prospective fertility and not a genetic evaluation. Factors considered for the revision of the model were date of insemination, age of cows at the time of mating and number of matings. Data included 3,726,450 records from 3,210 bulls and 1,312,901 cows in 7,395 herds from January 2011 till January 2016. Results revealed that alternative models ignoring AI organization and using only last five years of insemination, multiple services and editing on age of bull improved accuracy of predictions.