Long term effect of large-scale embryo transfer programs in the genetic structure and variability of Argentinean Polo horses: a 30 years retrospective

AZCONA, F.; MOLINA, A.; PIROSANTO, Y.; VALERA, M.; PERAL-GARCÍA, P.; TRIGO, P.; DEMYDA-PEYRÁS, S.

JOURNAL OF EQUINE VETERINARY SCIENCE

ELSEVIER SCIENCE INC

Año: 2020 vol. 89

0737-0806

Argentinean Polo horse is a breed created by selecting crossbredindividuals based on their performance in the polo game.During the last 30 years, breeding was based on large-scale ETprograms. These biothecnolgy has been associated with changesin the genetic structure of livestock populations (Azcona et al.Livestock Science. 2020, 231: 103848). However, long-term analysisof its effect in a horse breed is still absent. Therefore, weanalyzed the effect of the massive use of ET on 6 genetic populationparameters in the Argentinean Polo horse during the last 30years. To this end, 56924 foaling records reported between 1987and 2016 obtained from Argentinean Polo Horse stud book publicdata base were clustered in periods of five years (Table 1). Thepercentage of ET produced horses (ET%), average relatedness (AR),effective number of founders (Fe) and ancestors (Fa), and effectivepopulation size (via individual increase in inbreeding, Ne) wereestimated using ENDOG package. Statistically significant differencesin AR and ET% between groups, were estimated by ANOVAand post-hoc LSD test. Finally, correlations between ET% and thoseparameters were calculated. Our results show a steady increase inthe use of ET over the years, accounting for more than 50% of thefoals born during the last decade analyzed.We also demonstrateda parallel reduction in the variability and genetic base of thepopulation (with correlations close to -1 observed between ET%and Fe and Fa) but also an increased relatedness (Table 1), as wellas a increasing genetic bottleneck shown by the increase of the Fe/Fa ratio in correlation with ET%. All these changes were particularlysignifying during the last 15 years when ET% accounted formore than 30% of the foals. Despite that there is no phenotypicdata, our results strongly suggest that the ET programs areresponsible for the increased selection process towards the sportphenotype observed during the last 15 years in the ArgentineanPolo horse.