THE EFFECTS OF DIETARY FIBER, LACTOSE AND ANTIBIOTIC ON THE LEVELS OF SKATOLE AND INDOLE IN FECES AND SUBCUTANEOUS FAT IN GROWING PIGS

The effects on the production of indoles of dietary fibre, lactose and antibiotic were examined in a factorial design using 16 crossbred pigs (eight boars and eight gilts) from 40 to 90 kg live weight. The control diet was based on wheat and soyabean meal which was partially replaced either by sugar-beet pulp (400 mg/g) or lactose (25 mg/g) or both. All diets were offered with or without the antibiotic tylosin phosphate (200 mg/kg diet). Animals were penned individually and the diet restricted to provide 1.3 MJ digestible energy per kg M0.75. All faeces were collected for two 4-day periods at about 60 and 75 kg live weight. Animals were slaughtered on completion of the experiment and subcutaneous fat was sampled. Faeces and carcass fat were analysed for skatole and indole. There were no significant effects of treatments on growth rate but killing-out proportion was reduced (P < 0.05) on fibre or lactose diets with an additive effect (P < 0.001) of the combined ingredients. Dietary fibre significantly increased the daily elimination of skatole and indole and the concentration of indole in faeces but because of greater faecal bulk on the fibre diet the concentration of skatole in faecal dry matter was higher (P < 0.05) on the control diet. Dietary lactose had no effect on indole in faeces but significantly reduced the concentration and daily output of skatole. Levels of both skatole and indole in faeces tended to be reduced with dietary antibiotic which had a significant interaction with the fibre treatment on indole levels. The concentrations of skatole or indole in subcutaneous fat were neither affected by dietary treatment nor significantly correlated with concentrations or outputs in faeces.