Naturally and stimulated levels of reactive oxygen species in cooled stallion semen destined for artificial insemination

• The decrease in foaling rates after artificial insemination with cooled semen warrants the search for new predictors of fertility.The objectives were to investigate levels of naturally occurring reactive oxygen species (ROS) in cooled, stored stallion semen dosesfor artificial insemination (AI), and their relationship with parameters of semen quality and with pregnancy rate. Semen wascollected from warmblood stallions (n=15) and used to prepare commercial semen doses for AI. Sperm quality was evaluatedafter cooled transport to the laboratory overnight. The results were correlated with observed foaling and pregnancy rates.Hydroethidine and dichlorodihydrofluorescein diacetate were used as indicators for the ROS superoxide and hydrogen peroxide, respectively. Sperm morphology, motility, plasma membrane integrity and chromatin integrity were also evaluated. Thesevariables were correlated with each other and with pregnancy rates. We found a high inter-individual variation in the ROS levelsbetween stallions. The proportion of live, hydrogen peroxide-negative spermatozoa was correlated with progressive motility,whereas live hydrogen peroxide-negative spermatozoa and chromatin damage were negatively correlated, indicating that lowlevels of hydrogen peroxide were correlated with good chromatin integrity. The percentage of dead hydrogen peroxide-positivesperm was negatively related to the foaling rate. The negative relationships were stronger when combining results from bothassays for ROS. These results for stored semen samples indicate that high individual variation exists for superoxide and hydrogenperoxide measurements, and that ROS status can influence sperm quality. Thus, ROS may be some of the factors influencingfertility. Moreover, combinations of ROS variables improved the correlation with fertility, indicating the usefulness of includingthese variables in a future model for prediction of the fertility of a semen sample.

Ämnesord

LANTBRUKSVETENSKAPER  -- Veterinärmedicin -- Annan veterinärmedicin (hsv//swe)

AGRICULTURAL SCIENCES  -- Veterinary Science -- Other Veterinary Science (hsv//eng)

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