EFFECT OF GONADAL-HORMONES IN MATURE CYCLIC SOWS ON FOOD-INTAKE AND SKATOLE CONCENTRATIONS IN FECES

Bacterial degradation of tryptophan in the large intestine of pigs results in the formation of skatole (3-methyl lindole). This substance with a fecal malodour is accumulated in tissues. Sex differences had been found, with higher concentrations in boars compared to gilts. An effect of the ovarian hormones on food intake and skatole concentrations in faeces was investigated in mature cyclic sows (7 oestrous cycles from 4 sows) and in one sow which developed cystic ovaries during the investigation. Concentrations of progesterone and oestradiol were measured radioimmunologically in bloodplasma, skatole was determined by HPLC. Food intake varied considerably during the cycle. It was minimal (2.2 kg/day) during the oestrous period (low progesterone and high oestradiol concentrations), but high (5.3 kg/day) during the luteal phase. The mean levels of skatole varied between 5 and 18-mu-g/g dry matter with lower concentrations during the luteal phase and higher levels during the period of low progesterone. In the cystic sow skatole concentrations reached 50-mu-g/g during the period of low progesterone and high oestradiol concentrations. It is likely that ovarian hormones exert their effect on skatole formation mainly by regulating food intake and the contractility of the small intestine.