Analysis of spermatogenesis in young male hybrids bred from domestic cattle (Bos taurus) and European bison (Bison bonasus)

Abstract

A new attempt was undertaken to check the reproductive capabilities of male hybrids bred from European bison (Bison bonasus)and domestic cattle (Bos taurus). The analysis concerned two hybrids aged 1.5–2.5 years (the latter being sampled twice at 6-monthintervals), and additionally one 1.5-year-old backcross hybrid. Examination of testicular tissue revealed halting of spermatogenesis,which was hardly ever able to proceed further than meiosis I. Spermatogenesis was arrested at the stage of spermatogonia and primaryspermatocytes. Spermatozoa were found only in the case of one hybrid and these were mostly malformed. To summarize, all the malesstudied were sterile, despite the evident sexual behavior exhibited by one individual.