Influences on thermo-resistance of boar spermatozoa.

The aim of this study was to investigate the influence of semen production management in 25 European boar studs on thermo-resistance (TRT) of boar spermatozoa. TRT is an important semen characteristic, easy to determine, and is used to explain variations in pig fertility. During a study period from 2013 to 2018, 905 ejaculates were analyzed for TRT on day 7 of semen storage. Statistical models showed that around 40% of the total variability in TRT could be explained by production management factors. Significant selected predictors were year, month, boar stud, boar age, dilution steps, mitochondrial activity and membrane integrity of spermatozoa, bacterial contamination, arrival temperature of ejaculates in the analysis laboratory, sperm concentration, ejaculate volume, sperm output, dose/ejaculate, and electrical conductivity of pure water for extender preparation. TRT increased during the study period. No effects were observed for breed, dilution rate, morphologically intact spermatozoa, and refractive index of extender on TRT. A holistic view of the requirements in the field of boar semen production is of great importance for future developments of individualized Hazard Analysis and Critical Control Point concepts, prognosis models for boar semen quality, and could help to improve the efficiency of AI organizations.