Using sensor-derived estrus dates to improve the genetic evaluation of fertility in the New Zealand dairy industry

Abstract

Reproductive performance remains a cornerstone for farm profitability in New Zealand’s pasture-based dairy systems. Most NZ farmers maintain a strictly annual and tightly condensed calving period to synchronize herd feed demand with seasonal pasture growth. The interval from calving to first insemination (post-partum anestrus interval; PPAI) has been recognized as a useful candidate predictor trait for fertility EBVs, but widespread phenotype collection has historically been hindered by the expense and logistical challenges associated with serial blood testing or vigilant visual observation. With the advent and rapid adoption of activity sensors, LIC now has available a large and expanding dataset of estrus events, enabling efficient and scalable derivation of a range of fertility-related traits, including PPAI. Preliminary analyses demonstrate that PPAI has a heritability of around 0.12 and exhibits a moderate genetic correlation of -0.57 with timing of pregnancy (i.e. conception success within the first 42-d of the breeding period is associated with shorter PPAI). These preliminary results support PPAI as a useful predictor phenotype for fertility EBVs.  Furthermore, the availability of routinely recorded estrus dates for individual cows creates new opportunities for investigating other novel fertility phenotypes, such as length and regularity of estrous cycles, early confirmation of pregnancy and differentiation of conception-failure and early pregnancy loss.  Integrating sensor-based estrus detection into the national fertility evaluation is likely to increase the rate of genetic improvement for fertility in the NZ dairy herd, driving improved reproductive performance, and therefore cow longevity.