Elimination of the Ferguson reflex by section of the pelvic nerves in the lactating goat.

Abstract

SUMMARY Distension of the vagina by an inflated balloon induces milk ejection in goats. This reflex (the Ferguson reflex) is based on a neurohormonal mechanism. In three goats the reflex was abolished after bilateral section of the complex pelvic nerves plus caudal rectal nerves. Bilateral section of the pelvic nerves only, caused a complete elimination of the reflex in 11 out of 13 goats; in the two remaining animals, the reflex was abolished after a supplementary section of the pudendal nerve plus caudal rectal nerves. The reflex remained intact in one goat in which first the caudal rectal nerves and subsequently the pudendal nerve were cut. Elimination of the Ferguson reflex was accompanied by a marked reduction of the intensity of straining movements which are normally induced by distension of the vagina. Bilateral section of the pelvic nerves provoked a severe but temporary paralysis of the large intestine with blocking of the defaecation reflex. It is suggested that in ruminants the afferent pelvic nerves are involved in the release of oxytocin and in the intense straining occurring during the phase of expulsion at parturition.