Strategies to Reduce Methane Emissions in Lamb Finishing Systems in Brazil.

The contribution of livestock to global methane emissions is still uncertain, particularly when animals graze tropical pastures. The Brazilian sheep industry is based on grazing systems, so it necessary to assess strategies that lead to a less impact. The research objective was to assess the effect of concentrate supplementation in grazing systems, for lamb methane emissions. Two experiments were conducted during 2012/13 at two different regions of Paraná state, characterized by a subtropical climate. The experimental design was randomized blocks with two treatments and four replications, with three animals per plot. Two finishing systems were evaluated: S1 – early weaned lambs, kept on pasture and supplemented daily with concentrate at 2% of BW until slaughter weight, of 40 kg; S2 - lambs kept with their mothers on pasture until slaughter weight, of 40 kg. Animals grazed continuously on a pasture composed by ryegrass (Lolium multiflorum Lam) oversown on Tifton-85 (Cynodon spp) (1st year) and a mix of Tifton-85 (Cynodon spp) and Paspalum spp (2nd year). Stocking rate was adjusted to allow 12% of forage offer according to 'put and take' technique. Concentrate supplement was provided at 04pm in individual caged feeding points, to estimate daily concentrate intake. Daily methane (CH4) emissions were quantified using the sulfur hexafluoride (SF6) technique. Permeation capsules, previously calibrated, were administered orally before animals received gas collector apparatus. Two blank tubes collected atmospheric air, and background methane deducted in emission calculations. The emissions were calculated by the formula: QCH4 QSF6 x = ((CH4 B – CH4)/(SF6 B - SF6)). Results indicated higher (P<0.05) daily emission for supplemented lambs, that may be partially explained by their higher DMI, resulting from an additive intake effect. Results indicate that concentrate supplementation under pastures presents moderate mitigation potential. Therefore, forage offer may be responsible for animal’s higher quality diet selection with positive result over methane emission.
Keywords: concentrate, greenhouse gases, mitigation strategies, tropical pastures, sheep