The effect of synchronized breeding on genetic evaluations of fertility traits in dairy cattle: Preliminary analysis.
Hormonal synchronization alleviates the pressure of estrus detection by affecting the estrous cycle, allowing for higher rates of conception even for naturally low fertile animals. This leads to genetically inferior cows’ performance becoming masked and potentially resulting in similar performance to that of naturally fertile animals. As genetic programs rely on the collection of accurate phenotypic data, phenotypes recorded on treated animals likely affect the genetic evaluations. This study analyzed the traits calving to first service (CTFS), first service to conception and days open in 419,102 cows from 1122 herds with 1,811,394 breeding and fertility records across 3 scenarios. Scenario 1 compared records that included any type of hormone treatment (HORM) against all other records. Scenario 2 compared HORM vs heat detection protocol (HD) records. Scenario 3 compared hormonal synchronization protocol (FTAI) records vs HD. Available data for each trait was characterized based on the use of hormone treatment, for example CTFS was split whereby one subset included only FTAI records while the second data set included only HD records. Preliminary statistics are presented in Table 1. By conducting a bivariate analysis the results of this study will identify potential genetic and non genetic differences between the fertility phenotypes recorded under the different scenarios. In addition, this will provide a novel basis in assessing the impact of hormonal synchronization protocols on the accuracy of genetic evaluations for fertility traits in dairy cattle.