A team of researchers in Canada said they have been exploring the use of different feed ingredients on methanogenesis as part of an ongoing effort to establish a fact-based context for discussions regarding greenhouse gas (GHG) emissions in animal production.
Karen Beauchemin, corresponding author and research scientist with Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, said while there has been increasing data published on the contribution that livestock and cattle, in particular, make to global warming, the literature often contains conflicting information.
There is also limited findings on how diet influences emissions and the amount of gas that cattle generate, said Beauchemin.
The team has been examining feed additives, grains, soil carbon sequestration and farm management to continue to improve cattle efficiency and reduce additional greenhouse gas production.
“Biologically, going over the last 30 years, [industry has] reduced methane emissions per kiloliter of milk or kilogram of beef by about 15%,” she said.
And by addressing methane generation in cattle production, an additional benefit has been improved efficiency in the cattle, she added.
“Improving efficiency of production and improving production will, inherently, reduce methane emissions,” said Beauchemin. “It’s not about reducing methane, it’s about improving production of meat and milk, and better performance – all of those will [reduce] methane.”
In looking at the entire production system, the group also considers factors like soil health and carbon sequestration, she said.
“What we’ve found is, if you graze the grassland more intensively the quality of the feed is better – it’s less mature, so you have less methane produced,” she said. “But if you over graze it, then you have detrimental effects to the soil health. The key is to adopt grazing management that promotes long term sustainability of pastures, while maximizing animal gains to decrease total methane output."
Rather than aiming for a specific methane reduction target level, it can be more important to evaluate the overall operation and see if there are areas to improve, said Beauchemin.
“Legume forages versus grasses can be beneficial, or corn silage that has a lot of starch compared to small grain silage compared to grass silage [and] adding unprotected fats to the diet lowers methane emissions, but there’s only so much that can be added,” said Beauchemin.
Changes made will have more of an effect when done at an industry-wide level, rather than only on select farms, she said.
A synthetically produced compound – 3NOP – when included in the feed of the animals, blocks the enzymatic pathway that is used to synthesize methane, she said. However, the feed additive has to be given daily, which would work for a dairy or feedlot scenario, but would be more difficult for range-fed animals, said Beauchemin.
“In the last two studies we did, where we feed the 3N0P, we found animals had methane production reduced by 30-50% and they were more efficient,” she said. “They used more of the energy from the feed toward average daily gain.”
However, that particular additive has yet to be approved for use in Canada, said Beauchemin. “It has to undergo a lot of safety testing and that is still going on,” she added.
The group is also examining feed ingredients that include tannins, she said.
“[There are] a couple of studies right now looking at tannins with nitrogen excretion,” she said. “We’ll have a lot of new information in six months to a year – already we have some results, starting to see some conclusions.”
The initial work examining tannin-containing legumes appears positive, she said. “Legumes have a much superior advantage over grasses in lowering methane emissions, and if you keep them immature they have high energy,” she added.
Another piece of research underway at the Canadian center is the evaluation of concentrated tannin extracts as feed additives in a controlled system, she said.
Recently published research
The results of on the Canadian team's projects was recently published in the journal, Agricultural Systems, in which the group compared the use of corn silage to barley silage in dairy cattle diets.
Corn silage is being used more regularly as it is high energy and has been linked to a drop in ruminal methanogenesis, said the authors.
The study tracked whole farm total GHG emission and intensity in a dairy production system using a virtual farm and following a six-year life span for a dairy cow.
The group also examined the effect of silage digestibility on total GHG emissions. Their assessment considered methane; CO2 from farm operations and purchased feed; and N2O from crop residue, manure, leaching and volatilization.
Methane was predicted based on animal energy requirements and diet makeup.
The group found when a diet involving silages had a medium total digestible nutrient (TDN) content, total GHG emissions were reduced by 13%. But the reduction was partially offset by an uptick in CO2 emissions as a result of producers needing to purchase additional feed protein sources.
They said GHG intensity could be further reduced if producers used a highly digestible barley forage rather than if they used a corn silage of low digestibility.
“In that paper what we found was that corn silage reduced methane, but you buy more supplements so you have to account for the entire system,” said Beauchemin. Looking at the entire system can reduce unintended consequences, she added.
Source: Agricultural Systems
Title: Comparison of greenhouse gas emissions from corn- and barley-based dairy production systems in Eastern Canada
Authors: J Guyader, S Little, R Kröbel, C Benchaar, K Beauchemin