Potential of Samanea saman pod meal for enteric methane mitigation in crossbred heifers fed low-quality tropical grass

Abstract

Pods of Samanea saman have been reported to be effective in mitigating methane (CH4) emissions in ruminants. The aim of this study was to evaluate the effect of inclusion of S. saman pod meal in the ration on feed intake, apparent digestibility, rumen fermentation, rumen degradation, protozoa population, and enteric CH4 emissions in crossbred heifers fed low-quality tropical grass. Four crossbred heifers (Bos taurus × B. indicus) with an average live weight (LW) of 261.5 ± 1.29 kg were used in a 4 × 4 Latin square design with four periods of 23 days (17 days for adaptation and 6 days for measurements of response variables). Levels of inclusion of S. saman ground pods in the ration were 0, 10, 20 and 30% of dry matter (DM). Enteric CH4 emissions were measured using open-circuit respiration chambers. Additionally, rumen degradation of the different components of S. saman pods was assessed. Incorporation of S. saman levels had no effect on dry matter intake (DMI) (P > .05), apparent digestibility of dry matter (DM) and organic matter (OM) (P > .05) nor protozoal count (P > .05). It was found that molar proportion of propionic acid in rumen liquid was increased (P < .05), while that of acetic acid and acetic:propionic ratio was linearly decreased (P < .01) when heifers were supplemented with S. saman. Additionally, emissions of enteric CH4 showed a linear reduction as the inclusion of S. saman in the ration was increased (P = .007). A reduction of 50.9% in L CH4/day and 56.9% in L CH4/kg DM intake was observed at the highest inclusion level of S. saman compared to the control diet (P < .05). Potential degradation of DM of pods of S. saman was 79.6%. It is concluded that, the inclusion of S. saman pods in the ration has the capacity to reduce energy losses in the form of methane emissions in heifers fed low-quality tropical grass.