Effects of source and level of fibre in pig diets on methane production from pig faeces

Abstract

Fibres from a number of different sources (oat hulls, maize hulls, lupin hulls, maize cobs, soya bean hulls, pea hulls, wheat bran, lucerne stems and lucerne leaves) were fed to pigs at different levels together with a basal fibre-free diet, and the resulting faeces were used to measure methane production in laboratory scale digesters. The amount of methane produced ranged from 71·8 ml g −1 for faeces from the lucerne leaf diet, fed at a level of 5% fibre in the diet, to 226·8 ml g −1 for faeces from the wheat bran diet, fed at a level of 30% fibre in the diet. The amount of methane produced per gram of Volatile Solids destroyed ranged from 184·8 ml for faeces from the maize hull diet, fed at the 22·5% fibre level, to 337·2 ml for faeces from the wheat bran diet, fed at the 30% fibre level. The time taken for 50% of the possible methane to be produced ranged from 56 h for faeces from the lucerne leaf diet fed at the 20% fibre level to 179 h for faeces from the pea hull diet fed at the 30% fibre level. The Volatile Solids destruction ranged from 34·0% for faeces from the lucerne leaf diet fed at the 10% fibre level to 80·4% for faeces from the maize hull diet fed at the 30% fibre level. It is concluded that different sources of fibre in the diet of pigs, and different levels of feeding, can result in widely differing characteristics of pig faeces in terms of methane production under conditions of anaerobic digestion.