Induction of fertility and pregnancy in the anœstrous ferret

Abstract

Bissonnett (1932) was able to induce complete œstrus in three female ferrets by evening illumination from October 12 onwards, but similar treatment of a male from October 12 to December 22 failed to carry spermatogenesis beyond the spermatocyte stage. Mating, therefore, resulted only in pseudopreganancy. In a second series of animals illuminated from December 7 onwards, spermatorgenesis was secured during February and a litter was born on April 11 (Bissonnette, 1933). The normal untreated male, however, usually becomes fertile during February (Allanson, 1932) and the first litters of the season may be born early in April, so that Bissonnette cannot be said to have induced fertility outside the limits of the normal breeding season. Bissonnette’s failure to bring about premature spermatogenesis, though involving one animal only, suggested that the male was much more refractory than the female, especially since anterior lobe extracts and urine of pregnancy extracts readily cause ovulation in the anœstrous ovary (Hill and Parkes, 1930), while such extracts cause little reaction in the quiescent winter testis. It seemed, however, that a combination of additional light and gonad-stimulating extracts might be effective, and the present paper records experiments carried out on these lines, as a result of which pregnancy was induced in light-treated females well outside the limits of the normal breeding season.