[Clinical aspects of fertility in stallions]

The studies described in this thesis investigated the factors that can affect the fertility of stallions. The introduction describes the male gamete and the processes that occur during maturation of sperm and fertilization. Methods to evaluate the quality of sperm and ova are then discussed. Fertility can be expressed in various ways and is also affected by many factors such as the stallion, the mare and management factors. The fertility of stallions is usually assessed a good year after they have served mares, because then the number of foals is known. However, it would be preferable to be able to predict a stallion's fertility before he is put to stud. To this end, it was investigated whether there is a relationship between a number of sperm parameters and the percentage of non-return after the first cycle. The endocrine control of reproduction is briefly described because hormonal factors can also influence the reproductive potential of stallions. The venereal diseases that are important for regulations concerning the international trade in sperm are also described. The relevance of this diseases to reproduction deserves further investigation. The minimum requirement for a stud stallion is that the stallion should produce sperm of adequate quality and should be able to fertilize mares.