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

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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.

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Methane emissions from cattle.

K A Johnson, D E Johnson (1995)

Increasing atmospheric concentrations of methane have led scientists to examine its sources of origin. Ruminant livestock can produce 250 to 500 L of methane per day. This level of production results in estimates of the contribution by cattle to global warming that may occur in the next 50 to 100 yr to be a little less than 2%. Many factors influence methane emissions from cattle and include the following: level of feed intake, type of carbohydrate in the diet, feed processing, addition of lipids or ionophores to the diet, and alterations in the ruminal microflora. Manipulation of these factors can reduce methane emissions from cattle. Many techniques exist to quantify methane emissions from individual or groups of animals. Enclosure techniques are precise but require trained animals and may limit animal movement. Isotopic and nonisotopic tracer techniques may also be used effectively. Prediction equations based on fermentation balance or feed characteristics have been used to estimate methane production. These equations are useful, but the assumptions and conditions that must be met for each equation limit their ability to accurately predict methane production. Methane production from groups of animals can be measured by mass balance, micrometeorological, or tracer methods. These techniques can measure methane emissions from animals in either indoor or outdoor enclosures. Use of these techniques and knowledge of the factors that impact methane production can result in the development of mitigation strategies to reduce methane losses by cattle. Implementation of these strategies should result in enhanced animal productivity and decreased contributions by cattle to the atmospheric methane budget.