Foaling number are highly affected by the genomic homozygosity in the Pura Raza Spanish mares

LASECA, N.; PERDOMO-GONZÁLEZ, D.I.; VALERA, M.; MOLINA, A.; SANCHEZ-GUERRERO, M.J.; AZCONA, F.; PIROSANTO, Y.; DEMYDA-PEYRÁS, S.

JOURNAL OF EQUINE VETERINARY SCIENCE

ELSEVIER SCIENCE INC

Año: 2020 vol. 89

0737-0806

Fertility traits are pointed out as one of the most important breeding values in livestock production. However, they were scarcely evaluated in horses, probably due to the lack of phenotypic data as well as the effect produced by the variations in the reproductive management associated with different breeds andactivities. Among them, foaling number (FN), determined as the number of foals produced per year of reproductive life, is considered an interesting reproductive trait since it is influenced at the same time by the fertility and the longevity of the individuals. But studies assessing its genetic component in a large dataset of individuals are still absent. Additionally, molecular inbreeding (the actual degree of homozygosity molecular-values, (FROH) it was also associated with fertility in livestock. In this study, we evaluated the effect of F ROH in the foaling number estimated breeding value (EBVFN) in 243 Pura Raza Español mares (PRE). EBV?s were estimated based on 72,982 phenotypical records belonging to the PRE studbook using a bivariate REML model implemented in the VCE-6 package. The model included breeding stud size, owner stud size, owner stud country and birth year of the mother and the age of mare as a covariate. Molecular-based inbreeding values were estimated individually as the percentage of the genome harboring runs of homozygosity (FROH) using 600,345 SNP markers (27,569 from ECAX) through the Axiom Equine genotyping array (Affymetrix). FROH values were also determined using ROH longer than 16Mb (FROH16; depicting a recent increase of inbreeding) as well as only SNP markers located in ECAX (FROHX). EBVFN ranged from -1.72 to 2.78 depicting an ample genetic variation for these traits. Similarly, FROH and FROHX varied from 0.005 to 0.3986 and 0 to 0.969 respectively (with an average of 0.1461) also showing an ample variability in terms of homozygosity. Our results also determined the existence of a large negative correlation (r¼-0.398; p