Influence of Boars on the Relationship between Fertility and Post Thawing Sperm Quality of Deep Frozen Boar Spermatozoa*

Abstract

The aim of this investigation was to evaluate the possibility of selecting boars for deep freezing by means of laboratory tests on frozen-thawed spermatozoa. Thirty-one randomly selected frozen ejaculates from four boars were investigated by a thermoresistance test after thawing in boar seminal plasma and in OLEP. Extracellular ASAT activity was measured in samples from 30 of the ejaculates after thawing in OLEP and in isotonic glucose solution. Twenty of the ejaculates were utilized for fertility tests by artificial insemination of 37 gilts preceding the laboratory investigation. Three of the boars proved fertile with frozen semen. One of these boars seemed to yield superior fertility to the other two boars. No fertility was obtained with frozen spermatozoa from the fourth boar. Prior to the freezing trial this boar had been used for fresh semen inseminations giving higher pregnancy rates than the average of Swedish A.I.-boars. This boar was therefore considered a case of “low freezability”. In the laboratory tests the samples from this boar showed the lowest motility after 3 hrs.’ storage at 37°C, the highest relative decrease of motility during the thermoresistance test, the highest release of ASAT after thawing in OLEP and the highest relative release of ASAT. Analyses of variance indicated significant and almost significant variation among boars in relative decrease of motility during the thermoresistance test and in relative release of ASAT. The results indicate that the boars were the main cause of variation in fertility as well as in outcome of the laboratory tests. These results do not permit a complete evaluation of the relationship between fertility and outcome of the applied laboratory tests. However, the results indicate a possibility of detecting boars producing spermatozoa with low freezability by means of laboratory tests.