Methane emissions from cattle

Abstract

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.

An evaluation of the accuracy and precision of methane prediction equations for beef cattle fed high-forage and high-grain diets

“…High-grain diets promote fermentation of non-structural carbohydrates and propionate production that provides a competitive pathway for hydrogen use in the rumen, thereby decreasing CH 4 production (Johnson and Johnson, 1995;Beauchemin et al, 2009). …”

Impact of adding nitrate or increasing the lipid content of two contrasting diets on blood methaemoglobin and performance of two breeds of finishing beef steers

“…Basal diet and treatment effects Feeding diets containing a high proportion of cereals has been shown to reduce enteric CH 4 production compared with forage-based diets (Johnson and Johnson, 1995;Moss et al, 1995;Mc Geough et al, 2010;Rooke et al, 2014). This strategy is attractive, in that accompanying improvements in animal performance and efficiency has been demonstrated (Lovett et al, 2003;Mc Geough et al, 2010).…”

“…This is achieved through various mechanisms: fatty acids are not fermented in the rumen and therefore increasing dietary lipid concentration reduces the proportion of feed which is fermentable within the rumen; lipids can also reduce CH 4 production by coating fibre particles, reducing their digestibility, and by reducing the numbers and activity of the rumen methanogens and protozoa responsible for methanogenesis (Johnson and Johnson, 1995;Patra, 2013). Dietary lipid can be increased through the addition of pure fats or oils to the diet or through the use of by-products from distilleries, breweries or plant oil extraction as ingredients in the diet (Brask et al, 2013).…”

Enteric and manure-derived methane and nitrogen emissions as well as metabolic energy losses in cows fed balanced diets based on maize, barley or grass hay

“…It is often claimed that forage-based diets generally result in considerably higher enteric CH 4 formation than mixed or concentrate-based diets (e.g. Holter and Young, 1992;Johnson and Johnson, 1995;Boadi et al, 2004). However, the IPCC (2006) assumes lower enteric CH 4 only when diets for dairy cows contain more than 90% concentrate and does not differentiate between diets with lower concentrate proportions.…”