Assessment of fertilizing capacity of bull semen based on in vivo and in vitro assays

Abstract

The aim of this work was to evaluate the fertilizing capacity of bulls on the basis of the assessment of fresh and thawed semen, following the swim-up procedure and immunological assay with IgA and IgG antisperm antibodies. In addition, the suitability of immunological reaction with IgG and IgA antisperm antibodies for seminological assessment of bull semen was examined. Tests were conducted with semen originating from Holstein-Friesian bulls. Ejaculates were collected twice from 15 two-year-old males, yielding 30 samples of semen. After the calculation of sperm concentration and motility, the samples were diluted with Biociphos-Plus® and frozen in straws. After thawing, sperm concentration and motility were calculated again (an average of 101.4 million sperm/ml with a motility of around 21%), and the spermatozoa were subjected to swim-up. At the same time, frozen-thawed bull semen was tested for the presence of antisperm antibodies, using SpermMar Tests for IgG and IgA. According to the records of the insemination centre, 53 515 insemination treatments had been conducted with semen of selected bulls. In a population of 30 324 cows, the calculated insemination index amounted to 1.76. Half of the cows which were qualified for insemination had already been fertilized with the first treatment (ca 52.8%). After the swim-up, there was an average of 4.5 million hyperactivated spermatozoa with a motility of around 41%. Furthermore, spermatozoa associated with IgG antisperm antibodies were found in 20 ejaculates, i.e. in around 66.67% of all semen samples obtained. The spermatozoa reacted positively with IgA antibodies in as many as 23 samples, which constituted 76.67% of all ejaculates obtained. Correlations between the routinely analyzed semen parameters and the selected parameters (immunological, swim-up) which were demonstrated in this work, did not appear to be sufficiently convincing. Therefore, it seems necessary to repeat this study with a population of clinically healthy, fertile bulls, as well as with juvenile bulls newly introduced to the insemination centre or with bulls with reduced fertility.