Effect of Leucaena leucocephala on methane production of Lucerna heifers fed a diet based on Cynodon plectostachyus

A rapid growth of the meat production industry is necessary to satisfy increased demand for this commodity, which might have negative impacts on the environment. The objective of this study was to assess enteric methane (CH 4 ) emissions when a forage legume is introduced in the diet of animals consuming a tropical grass. Eight Lucerna heifers, 218±18 kg live weight with an average age of 19±3 months were used in two experiments following a changeover design. The diets evaluated were 100% star grass ( Cynodon plectostachyus, S ) or 76% star grass plus 24% leucaena ( Leucaena leucocephala , S+L). Throughout the experiment, animals were housed in two chambers, in which the diet was offered four times daily. Each chamber had a small wind tunnel, which housed a fan set to a constant speed of extraction. Air samples were obtained every hour during 24 h both inside and outside (ambient) the tunnel. Methane concentration in these samples was determined by gas chromatography. Temperature and relative humidity both inside and outside the tunnel were recorded using a thermo-hygrometer. The S+L diet had greater protein content whereas the S diet had greater content of neutral detergent fiber. Average intake (kg/d) of fresh forage and dry matter (DM) was significantly greater (23.7 and 5.6) for the S+L than for the S diet (18.9 and 4.7), respectively ( P P =0.32). These results suggest that while increasing animal productivity by increasing dry matter intake, the inclusion of leucaena does not increase methane emission per animal, thus significantly decreasing methane emissions per kg of meat or milk produced.