There is no question the ongoing narrative concerning climate change and the various “man-induced” gas (including ammonia, carbon dioxide, methane and nitrous oxide) emissions includes agriculture in numerous ways.

Whether or not we agree with the premise that changes in the earth’s weather patterns or climate in general are affected to any great extent by our activities is somewhat irrelevant. The discussion, political activism and governmental regulation are here to stay.

It is well-known this issue involves the dairy industry. It involves everything from the gases cows produce from eructation (burping) or that emitted from the opposite end (flatulence) to those produced from normal lagoon functions and by microbial activity on the pen surface.

The vast majority of gas production is related to microbial activity in the breakdown of nutrients, particularly fiber and other carbohydrates provided to the animal through the feeding program.

Much of this issue has played out in intensive dairy production states like California. Given their political and environmental regulatory positions, California dairies have been the target of scrutiny for years and, subsequently, have led the way for the entire dairy industry in greenhouse gas (GHG) mitigation.

Over recent years, California dairies and U.S. dairies in general have accomplished a great deal, including a 63 percent reduction in GHG emissions per gallon of milk produced since 1963. There has been a switch to greater uses of alternative energy sources, including the establishment and growth of the “digester” industry.

This has helped reduce the handling of manure and provided an alternative on-farm energy source. Finally, a 2013 study sponsored by the California Air Resources Board showed the dairy industry contributed a total of 4 percent of GHGs emitted in California. Similar results may also be seen across the U.S.

So as dairy producers take a wide variety of management steps to reduce gas emissions, largely from pen surfaces and waste-handling facilities, a subsequent question becomes: How does the basic nutrition and feeding of the cow affect GHG emissions on-farm?

Can we further reduce the production of gases like ammonia and methane by altering the feed ingredients used? One point we should remember is: Earlier research has shown feeding programs, products and additives that reduce production of these waste gases also serve to improve feed efficiency in the cow.

In other words, this results in an increase in energy retention that serves to meet maintenance and production energy requirements. The more we can develop programs that will retain critical nutrients in the body, the less fermentable material ends up on the pen surface or in the lagoon. This, in turn, helps reduce gas emissions. So from a different perspective, reduction in GHGs becomes a byproduct of a good nutrition program focused on maximizing feed efficiency (FE).

Improved feed efficiency equals reduced emissions

The main sources of emissions in dairy cattle are:

1. Eructation – A normal means of releasing gas production in the rumen. Failure to do this results in bloating. Very similar to that in people (burping). However, this process may also be part of the rumination process when undigested forages in the rumen are coughed up for further chewing.
   
   
2. Flatulence – Elimination of gases produced during digestion and any hind-gut fermentation
   
   
3. Pen surface – More common and plentiful in drylot and grazing dairies, although this is a source in freestalls as well
   
   
4. Lagoons
   
   
5. Fossil fuel use

So this boils down to two of the primary GHG sources on the dairy: animal and environmental. Feasibly, the producer has some control on both sources from a nutritional perspective.

Forages

As a feed group, forages have the greatest effect on FE and related emission levels. Since they generally make up the largest fraction of the slowly digestible part of the diet of lactating cows, forages are critical for targeting a desired FE. They also have a large impact on FE because they are the most variable feed ingredient in terms of digestibility and nutrient composition, and they comprise a greater proportion of the ration than any other feedstuff.

It has been shown FE is directly related to forage digestibility, with increased digestibility leading to increased FE and, subsequently, reduced emissions. Unless concentrates are uncommon, damaged or poorly processed to have damaged protein or other nutrients, they are commonly more digestible than forages.

Since energy density has the same relationship with FE, significant focus should be given when selecting forage varieties and practices at harvest, storage and feeding to achieve the highest-quality forage possible. These steps will improve FE and reduce emissions. Since forages can be variable, attention to changes and modifying rations accordingly is important.

Another way forages can positively influence FE is through the maintenance of a desirable rumen environment. Acidosis can negatively affect FE by decreasing fiber digestibility through changes in the rumen microbial populations. Adequate physically effective fiber in the ration will help maintain the proper rumen environment and general rumen health.

Grains, proteins, byproducts

In most situations, if proper concentrate-to-fiber ratios in the diet are maintained, increasing the concentrate portion of the diet will improve FE. As discussed previously, this is primarily related to increasing the energy density of the total diet and improved diet digestibility.

This is contingent upon maintaining proper rumen health through adequate fiber levels and the feeding of forages of proper particle sizes. Thus, proper ration balancing is critical.

Use of the basic grains (corn, barley, wheat) and protein sources (soybean meal, canola meal) work well in these situations. They are consistent and proven dietary components. The byproducts (distillers grains, corn gluten feed, hominy, etc.) are inherently more variable and can cause difficulty in maintaining consistent nutrient levels and digestibility.

This has been shown to challenge constant, stable FE and can result in increased emissions. So a focus on FE and emissions reductions require constant attention to the variation found in byproducts.

Feed additives

Recent research has shown a growing number of feed additives that can improve rumen function, FE and reduce GHG emissions. Feed additives such as specific enzyme sources (especially fibrolytic enzymes), yeasts, other direct-fed microbials and plant extracts/essential oils have been shown in a growing body of research to enhance diet digestibility and increase FE as it affects energy-corrected milk and component production.

Use of ionophores such as Rumensin have long been seen to improve feed efficiency. (Early research in feedlot cattle showed a significant improvement in FE, much of which was related to reduction in ruminal gas production.) Additional research is needed to identify the effects of various combinations of these products to optimize the effect.

Conclusions

The discussion concerning GHG production by the dairy industry is apparently here to stay and an evil the producer will have to endure. The positive side of this argument is the effect of improving management to comply with a growing group of regulations.

Likewise, the industry can potentially improve FE, resulting in greater profitability while producing reduced farm emissions. So depending on which way it’s viewed, a focus on emission reduction should also be coupled with improved feed efficiency, which is a very good outcome for the producer.  

PHOTO: Improved feed efficiency equals reduced emissions. Staff photo.

• Stephen B. Blezinger

• Management and Nutritional Consultant
• Reveille Livestock Concepts
• Email Stephen B. Blezinger