Pregnancy blocking experiments involving 731 female laboratory mice (control and experimental) indicate: (1) an increased resistance among older females; (2) an equal susceptibility among parous and non-parous females; and (3) a lower pregnancy rate among females exposed to six males than those exposed to one or three males.
The effect of the male preputial gland on the oestrous cycle in mice was investigated. Urine from preputialectomized (but otherwise intact) males was slightly but not significantly more effective in stimulating oestrus than urine from castrates, but it was significantly less effective than urine from intact males. Preputialectomized males inseminated fewer females with a less pronounced Day-3 peak of inseminations than intact males. It is concluded that the preputial secretion is at least partly responsible for the acceleration or synchronization of oestrus (Whitten effect).
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