89 Effect of embryo transfer and recipient breed on offspring performance in equine show jumping

Abstract

Maternal preconceptional, gestational, and postnatal environments alter offspring phenotype in humans and animals. In particular, embryo technologies were shown in horses and other species to affect offspring growth and metabolism. Quantitative genetic calculations in a database containing genealogy and a measured trait (performance) of individuals enable geneticists to estimate the respective contribution of (A) genetic aptitude for the trait (inherited from all parents), (B) genetic maternal aptitude (additional contribution of the mother and her ancestors, acting through pregnancy, lactation, and nursing), and (C) the permanent maternal environment (similarities between the offspring of a dam that are not attributed to genetics) to the variability of this trait in this population. Additionally, fixed effects can be introduced and estimated to take into account additional factors acting on individual performance. The aim of this project was to apply this method to estimate the respective contributions of A, B, and C as well as the fixed effects of maternal parity (D), age at foaling (E), foaling interval (F), embryo transfer (G), and breed of recipient mare (for ET recipients) on the adult offspring sport performance in show jumping horses. The data came from the French Horse Database established in 1976 for genealogy and performance; calculation was done using WOMBAT® software. The performance of 207,984 horses (4.5 years per horse), born to 90,438 dams (of which 4187 were ET recipients, the others being bred by AI or natural service), were studied. Performance was expressed as follows. For each event, points were distributed depending on the horse’s rank within the event and the event’s difficulty. The logarithm of the sum of points of the year has a Gaussian distribution and is then normalised to mean = 0 and standard deviation = 1. The genetic maternal aptitude and permanent maternal environment showed a small but significant contribution to the variance of performance (1.4 and 1.5%, respectively) compared to a direct genetic contribution of 24.4%. Within each age class of dam, offspring of primiparous mares have a handicap (−0.04 to −0.06) compared to multiparous mares. Within multiparous mares, a foaling interval of 1 year only provided a small advantage (+0.01, nonsignificant) compared to longer intervals (>2 years). The effect of embryo transfer was strong and significant (+0.24), which could reflect the better management of the horses produced by embryo transfer because of their genetic and financial value rather than a physiologic effect. The performance of offspring born to draft and warmblood recipients (+0.27 v. +0.24, nonsignificant) were not different. In conclusion, although jumping performance occurs several years after birth, maternal effects are still measurable and embryo transfer is associated with a strongly increased performance independent of genetic value, probably due to better management of these horses. No effect of recipient mare’s breed was found.