Effect of sunflower oil supplementation on methane emissions of dairy cows grazing Urochloa brizantha cv. marandu

The objective of the present study was to evaluate the effect of sunflower oil supplementation on methane (CH4) emission of crossbred Holstein x Gyr (Bos indicus) dairy cows grazing tropical pasture. Lactating dairy cows were fed Urochloa brizantha (syn Brachiaria brizantha) pasture managed under rotational grazing. Sunflower oil was supplemented to cows using concentrates with inclusion at 0% or 14.9% (DM basis). Crude fat concentrations in these concentrates were 2.4% and 13.8% respectively (DM basis). Dietary fat concentrations for control and supplemented sunflower oil treatments were 3.2% and 5.2% (DM basis) respectively. Sixteen lactating cows Holstein x Gyr (Bos indicus; 240 +/- 10 days in milk, 524 +/- 57 kg of bodyweight, 11.2 +/- 2.30 kg/day of milk) were used in the study. Methane emissions were estimated by the sulfur hexafluoride tracer technique. The experiment was a randomised-block design with two repetitions of pasture area, with two treatments (0 g or 383 g of sunflower oil supplementation, DM basis) and four replications (cows) per treatment per block. Methane emission and yield expressed as g CH4/day and g CH4/kg of DM intake decreased 21.5% (P=0.048) and 20.2% (P=0.032) respectively, in cows supplemented with sunflower oil compared with unsupplemented cows. There was no effect (P=0.29) of sunflower oil supplementation on CH4 expressed as g CH4/kg of milk. Lactating dairy cows grazing tropical-grass pasture supplemented with sunflower oil (5.3% dietary fat; 383 g oil/day) demonstrated potential for mitigating CH4 emissions without negatively affecting cow milk yield or composition.