New insights on feeding distillers grains to beef cattle
Understanding the complex implications for greenhouse gas emissions
Posted: June 18, 2013
Can distillers grains help reduce methane emissions from cattle?
The short answer is, "it depends," say Agriculture and Agri-Food Canada (AAFC) researchers investigating the question.
The longer answer shows the complexity of figuring out the greenhouse gas (GHG) emissions puzzle and why innovative tools such as AAFC's Holos software program are critical to help Canadian agriculture find solutions.
"GHGs from livestock production is an area where the options for reducing emissions are often not black and white," says researcher Dr. Tim McAllister of AAFC Lethbridge. "Distillers grains is a good example of that. What we need to do is look at all our options in the bigger picture and figure out what makes sense both for producers and industry as well as for addressing emissions."
"The big positive is we are already very efficient in beef production in North America," adds Martin Hünerberg of AAFC Lethbridge, who has led key studies along with McAllister and colleagues. "As we learn more that broader perspective will become clearer and help us find ways to fine tune and keep getting better."
Tackling the GHG challenge
Around the world a new wave of research activity is underway to improve the understanding of how livestock agriculture contributes to GHG emissions and help identify mitigation strategies to meet the rising expectations around this issue.
On the beef production side, an important part of this activity is to look more closely at feeding strategies that have the potential to deliver efficiency benefits and other advantages to the producer while also helping to reduce overall emissions. While top-tier beef production systems such those in North America are already considered highly efficient, researchers are optimistic that through the exploration of multiple strategies further emissions reductions of up to 20 percent are achievable over the next decade.
The task of identifying mitigation options and developing strategies, however, is proving a complex undertaking as researchers, industry and other stakeholders develop a better appreciation for the many layers and implications involved in GHG emissions. There are often wide-reaching ripple effects that any single change can have on the dynamics of a production system and the overall environmental outcomes.
This is the case with distillers grains from ethanol production, says McAllister. He is part of a team of AAFC researchers that has examined the potential benefits of feeding distillers grains to beef cattle from several angles, including what effects this has on GHG emissions. While initial studies found strong promise for certain approaches to reduce enteric methane – a major target of mitigation strategies - a broader look at the implications has shown a mix of positive and negative results.
"We have learned there are many things to consider," says McAllister. "Some approaches with distillers grains result in a reduction in enteric methane. However, they are also linked with an increase in manure nitrogen, which can result in high nitrous oxide emissions."
Depending on how producers manage the manure, there can be benefits to this nitrogen as well and a wide variation in the actual level of emissions that result, he says. There are also important economic considerations from a producer's perspective and a broader environmental picture to recognize.
"Even if distillers grains are an net negative from a GHG perspective, feeding them to ruminants can still be a good economic option for producers. This approach may also be the best option we have to make use of this by-product and prevent it going to a landfill or another undesirable consequence."
Supporting management decisions
In today's beef industry in Western Canada, the attention on distillers grains has shifted to the back burner of late. "There's not much distillers grain being used right now because the price relative to barley is quite a bit higher. But in the past there has been significant use of wheat distillers grains from local ethanol production and we've also seen a fair bit of corn distillers grains coming up from the U.S. The market and resulting usage of distillers grains is likely to continue to fluctuate."
The potential for a strong supply of distillers grains as a viable option for beef operations was a major reason why the AAFC researchers have conducted numerous studies examining the pros and cons of different feeding approaches with distillers dried grains and solubles (DDGS). As their role in conducting research related to GHGs in agriculture has expanded in recent years, the implications related to DDSG became another promising angle to evaluate.
In a first phase of this effort Dr. Sean McGinn at AAFC Lethbridge examined the effects of corn DDGS on enteric methane emissions. These grains, which typically had 10 to 12 percent oil content, showed a clear relationship to reduced enteric methane emissions.
"It appeared to be a good news story in terms of GHG emissions," says McAllister. "But it was only part of the picture."
Follow-up research, led by Hünerberg looked further into the question. In a trial with beef heifers, the researchers examined both the enteric methane and manure nitrogen results related to four different treatments. Part of the focus was to determine if it was actually the fat content of the DDGS that lowered the methane emissions. Corn DDGS effects were examined, as well as the effects of wheat DDGS, which has a much lower oil content. One of the treatments was a standard western barley based diet with no DDGS, for comparative purposes.
The results confirmed that DDGS can reduce methane emissions and this effect is greater with increasing oil content. However it also found that feeding DDGS greatly increased the manure nitrogen content. "Our study included DDGS at 40 percent of the ration, which does not typically occur commercially but would be about the maximum that would be feasible if the economics were favorable," says Hünerberg. "A common commercial ratio would include about 20 percent of DDGS. However, based on these results we can predict that even at the 20 percent level we would still be overfeeding nitrogen and increasing the potential for nitrous oxide emissions to a level that would offset any gains from a reduction in methane."
Holos tool supports life cycle perspective
As a result, the answer to the question of whether or not feeding distillers grains is good from a GHG perspective is not definitive, says McAllister. "Getting the best GHG results requires identifying specific details on rations that work best under different scenarios and factoring in the best options for managing manure."
That bigger picture perspective is something the researchers are now examining as part of a broader AAFC initiative that is based on use of a life cycle assessment model developed for beef GHG emissions.
The assessment was conducted through a multi-faceted research effort led by Dr. Karen Beauchemin that involved using the leading-edge Holos modeling software program. The assessment captures a comprehensive, whole farm view of what contributes to emissions from beef operations in Western Canada during the full life cycle of beef cattle, from birth to the farm gate, based on the most current knowledge available.
A baseline model has been developed with Holos and the researchers plan to continually enhance the model with new information as it is generated through further research studies, on farm surveys and other sources. The researchers can also use this tool to run different scenarios based on the information included in the model, to project the effects of different changes to production approaches.
"The DDGS questions we are investigating are ones we want to examine further from the complete life cycle perspective," says Hünerberg. "What we have learned in our recent studies will have value in contributing to the model, and we can use the model to get a better understanding of the implications of our findings."
Recent work to support this approach included using a separate GHG model program that uses a life cycle approach to calculate carbon footprints. The researchers used this model to establish values for biofuel by-products such as corn-based and wheat-based DDGS and canola meal, which can be used as model inputs for the Holos program. Canola meal was examined since this is another high protein biofuel by-product frequently used by Canadian producers.
Ultimately, there are always additional layers and questions to consider, particularly when looking at the overall environmental challenges facing the world and trying to get a balanced perspective on where agriculture fits, says McAllister. "GHGs are only one part of the environmental issue and agriculture is only one industry. Nothing operates in isolation and that's why we need sophisticated modeling tools to help us continually build a better understanding of where everything fits."