Abstract/Summary

Methane (CH4) production varies between herbivore species, but reasons for this variation remain to be elucidated. Here,we report open-circuit chamber respiration measurements of CH4 production in four specimens each of two non-ruminantmammalian herbivores with a complex forestomach but largely differing in body size, the collared peccary (Pecari tajacu, mean body mass 17 kg) and the pygmy hippopotamus (Hexaprotodon liberiensis, 229 kg) fed lucerne-based diets. In addition, food intake, digestibility and mean retention times were measured in the same experiments. CH4 production averaged 8 and 72 L/d, 18 and 19 L/kg dry matter intake, and 4.0 and 4.2% of gross energy intake for the two species, respectively. When compared with previously reported data on CH4 production in other non-ruminant and ruminant foregut-fermenting as well as hindgut-fermenting species, it is evident that neither the question whether a species is a foregut fermenter or not, or whether it ruminates or not, is of the relevance previously suggested to explain variation in CH4 production between species. Rather, differences in CH4 production between species on similar diets appear related to species-specific differences in food intake and digesta retention kinetics.