Relationship Between Sperm Quality Measures of Cooled-Shipped Semen and Fertility.

Abstract

Features of fresh stallion semen such as sperm concentration, motility, morphology, and DNA quality are routinely evaluated as part of a breeding soundness evaluation and diagnostically to determine the cause of reduced fertility, however, there is limited information about the relationship between these values in cooled-stored semen and stallion fertility. The goals of this study were to determine the relationship of stallion sperm quality features after 24 hr of cooled-storage on fertility. Sperm concentration and viability were determined using a NucleoCounter SP-100, DNA quality by the Sperm Chromatin Structure Assay, sperm motility by phase-contrast microscopy and sperm morphology by differential interference microscopy. Stallion (n=135; age (years)- mean-11; range-3-25) seminal parameters were evaluated during the 2009 breeding season and donor mares (n=204) were bred with cooled-shipped semen at an embryo transfer facility (Royal Vista Southwest, Purcell, OK) either the same day as collection or 24hr after semen collection. Fertility was determined by embryo(s) recovery. The percentage of embryos recovered was higher (65 vs. 51%; P < 0.01) when mares were bred with semen collected from the stallion on the same day compared to mares bred approximately 24 hr after semen collection. Pregnancy data were then compared to each individual seminal parameter in order to determine the relationship between sperm quality and resulting embryo recovery (fertility). Sperm parameters influencing the success of embryo recovery rate were: total sperm motility (P < 0.01), progressive motility (P < 0.077), total sperm number (P < 0.002), total motile sperm (P < 0.003), total progressively motile sperm (P < 0.002), viability (P < 0.004), total viable sperm (P < 0.002), total progressively motile viable sperm (P < 0.0001), %COMP (P < 0.045), morphologically normal sperm (P < 0.001) and total morphologically normal sperm (P < 0.0001). In a large group of mares and stallions this study identifies sperm features that affect fertility as determined by embryo recovery. This information will help horse breeders and researchers determine those sperm quality factors that maximize fertility. (poster)