The Effect of Synchronized Breeding on Genetic Evaluations of Fertility Traits in Dairy Cattle

Lynch, Colin
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University of Guelph

Through the use of timed artificial insemination protocols (TAI), it is possible to alleviate the pressure of estrus detection. However, TAI affects the reproductive physiology and endocrinology involved in the estrous cycle, leading to genetically inferior cows’ performance becoming masked. As genetic programs rely on the collection of accurate phenotypic data, phenotypes collected on treated animals likely add bias to genetic evaluations. In this study, to assess the effect of TAI, the rank correlation of bulls for a given trait using only TAI records were compared to the same trait using only heat detection records. Large re-ranking occurred between bulls compared based on either having 100% TAI records or 100% heat detection records, across all traits and parities, indicating that a bias does indeed exist. Methods to account for the bias created by TAI should be investigated, alternatively, fertility traits should be split via management technology into two independent traits.

fertility traits, hormonal synchronization, genetic evaluations