The variety of sterility and gradual progression to fertility in hybrids of the horse and donkey

Abstract

Generally speaking, the majority of F1 hybrids between the horse and donkey are sterile and do conform to the hypothesis of gametogenic breakdown. The results of our own research, nevertheless, lead us to conclude that there is variability in degree of sterility and fertility for both F1 and B1 individuals, with a gradual advance from sterility to fertility being seen. This is the subject we will discuss from the points of view of oestrus, ovulation, mating, pregnancy, spermatogenesis, endocrine activity, isozymes and karyotypic analysis in this paper. © 1989, The Genetical Society of Great Britain.