Using highly nutritious pastures to mitigate enteric methane emissions from cattle grazing systems in South America

Abstract

Enteric methane (CH4) emissions are directly related to the quantity and type of feed intake. Existing mitigation strategies, for example, the addition of legumes to grass-based diets and increased use of grains, have been thoroughly researched and applied in different production systems. In this paper, we propose a need to expand the capacity to mitigate enteric CH4 emissions in cattle under grazing conditions. The objective of this paper was to contribute to evaluate a mitigation strategy under grazing conditions of using contrasting levels of pasture quality. The study was performed with 20 heifers twice during the year: winter and spring. Each season, the study employed a crossover design with two treatments and two 5-day measurement periods. The treatments were two pastures with different nutritional values, including a pasture with a low quality (70% of neutral detergent fibre, 1% of ether extract, 8% of non-fibre carbohydrates), 9% of crude protein, 35% of dry matter digestibility and a pasture with a high quality (42% neutral detergent fibre, 1.3% ether extract, 24% non-fibre carbohydrates, 21% crude protein and 63% dry matter digestibility). Enteric CH4 emissions were measured with sulfur hexafluoride tracer technique. The dry matter intake (kg/day) was measured indirectly using titanium dioxide as an external marker. CH4 emissions from animals grazing the high-quality pasture were 14% lower expressed as % of gross energy intake, and 11% lower expressed by unit of dry matter intake (g CH4/kg). These results quantitative showed the alternative to mitigate CH4 emissions from grazing bovines exclusively through the improvement of the forage quality offered.