Increased genomic homozygosity affects negatively sperm longevity in Pura Raza Español stallions

DEMYDA-PEYRÁS, S.; LASECA, NORA; HIDALGO M; PIROSANTO YAMILA; CESARI ANDREINA; MOLINA ANTONIO

Nantes

Congreso; European Society for Domestic Animal Reproduction; 2023

The Pura Raza Española (PRE) is a renowned horse breed known for its physical and athletic traits bred in more than 60 countries. However, its elevated levels of homozygosity may have negative impacts on reproduction. This study investigated the relationship between increased genomic homozygosity and sperm longevity. To this end, we performed a 60-min in vitro longevity test on 2 ejaculates of 20 PRE stallions, evaluating sperm motilities (total (TM), progressive (PM), and fast-progressive (FPM) at 5 and 60 min after collection using a CASA system. Estimated breeding values (EBVs) were determined individually using a quantitative approach based on REML methodology, including the genomic inbreeding level of the individual, determined by a FROH analysis using SNP-array data, as a covariate. Results showed a large effect of inbreeding on sperm motility at T5 (an increase of 1.96%, 1.71%, and 0.48% in TM, PM, and FPM per each percentual point gained of inbreeding). On the contrary, the EBVs obtained after 1 h of incubation showed a significant negative effect of inbreeding on TM (-0.76%) and PM (-0.86%), whereas the effect estimated in FPM (0.23%) was not significant statistically. These findings support previous studies suggesting that increased inbreeding leads to an early onset of sperm movement increase, which may result in early depletion of sperm energy sources and reduced longevity, possibly affecting fertilization ability. In conclusion, increased genomic homozygosity negatively affects sperm longevity in PRE stallions, which may lower their reproductive success. Effective breeding programs are essential for maintaining genetic diversity to improve reproductive performance in PRE stallions.