Stallion Sperm Counts Rise After Exposure to Mares with Different Immune Genes
A 2018 study from the University of Bern found that stallions produced more sperm and higher testosterone levels when exposed briefly to mares with dissimilar major histocompatibility complex genes than when exposed to genetically similar mares. The full-factorial within-subject design controlled for wide variance in semen characteristics among individual stallions. Overall genetic similarity measured by polymorphic microsatellites on 20 chromosomes played no significant role. The MHC type of the teaser mare also affected cold-stored semen. Sperm viability increased after exposure to an MHC-dissimilar mare, consistent with ejaculate economics. But oxidative stress and the percentage of sperm with high DNA fragmentation mostly increased after exposure to an MHC-dissimilar mare, depending on whether the teaser mare was in oestrous.
Males can adjust ejaculate quality rapidly based on a female's MHC, and this reaction to the social environment affects important characteristics of cold-stored semen. The findings may inform equine breeding and semen storage protocols.
Written by the Genomes desk from the primary source linked above and checked against it. Research use only; not medical advice. Corrections: [email protected].