Methane emission of Blackbelly rams consuming whole sugarcane forage compared with Dichanthium sp. hay

Dietary strategies are options to mitigate enteric methane from ruminants. This trial has been performed to estimate the production of methane with a sugar-rich forage versus a high-fibre grass. Comparative intake, digestion and methane emission of whole Saccharum officinarum (sugarcane) plant and of Dichanthium sp. hay (from permanent grassland) were studied. Eight Blackbelly rams (40.1 ± 1.4 kg on average) were used in a 2 × 2 crossover design. All the animals received two diets ad libitum: whole sugarcane plant (WSC) supplemented with urea (4.2 g/kg dry matter) and a mature Dichanthium sp. hay (H). Measurements were: voluntary intake, total-tract digestibility, methane production using the SF6 method, rumen concentration of volatile fatty acids, ammonia and protozoa measured by counting. Organic matter intakes were similar between WSC and H treatments, averaging 48.0 g/LW0.75. Intakes of soluble carbohydrate (SC) were higher with WSC than with H (22.7 and 5.8 g/LW0.75, respectively for WSC and H; P < 0.01) .Total tract digestibility (g/kg) differed between WSC and H diets for both organic matter (712 and 647, respectively for WSC and H; P = 0.03) and neutral detergent fibre (510 and 693, respectively for WSC and H; P < 0.01), but not for crude protein (average: 477 g/kg). No difference was recorded between the diets for nitrogen apparently retained. Methane emissions (g/kg Digestible Organic Matter intake (DOM)) differed between diets (34.7 and 53.7, respectively for WSC and H; P < 0.01). Proportion of acetate in total volatile fatty acid (mol/100 mol) was lower with WSC than with H (average: 59 and 77, respectively; P < 0.01), whereas propionate (average: 23 and 15, respectively for WSC and H; P < 0.01) and butyrate (average: 15 and 6, respectively; P < 0.01) proportions were higher. Protozoa population in the ruminal liquid (105/ml) was similar with WSC and H (average: 1.34). In conclusion, our data indicate that in some tropical areas, methane production could differ between grasses and consequently a dietary strategy based on forage management is a realistic option to mitigate enteric methane from ruminants.