Fiber digestibility is a primary driver of feed efficiency, yielding performance, economic and sustainability benefits for dairy producers. Recently, extensive progress has been made in understanding the critical role that branched-chain volatile fatty acids (BCVFAs), also known as isoacids, play in improving the dairy cow’s ability to digest fibrous feedstuffs. However, in certain circumstances, cows are unable to meet their BCVFA requirements through the normal process of protein breakdown. This provides the opportunity for BCVFA supplementation to improve fiber digestion and performance.
Global Technical Services
Zinpro IsoFerm
Today’s marketplace pressures demand dairy producers do more with less as it is more important than ever for cows and operations to be productive, efficient and profitable while being sustainable. Fortunately, the dairy cow has a unique ability to turn fibrous human-inedible feedstuffs into milk via a beautiful, yet complex, digestive process. However, high producing dairy cows need a combination of human-inedible forages and fermentable carbohydrates to achieve their productive potential and yield the milk needed by our growing human population. Therefore, with greater focus on rumen function and efficiency, the dairy industry has the opportunity to provide greater output with less input. Improving fiber digestibility is key to unlocking greater efficiency by ensuring fiber-digesting bacteria in the rumen have adequate levels of required nutrients.
THE ROLE OF BCVFAs IN FIBER DIGESTION
First, we must understand how the rumen functions and for many nutritionists this may seem like an old story, but there are new insights. As we know, fiber digesting bacteria breakdown forages to make volatile fatty acids (VFAs) and microbial protein which the cow then utilizes to make milk, replenish her energy stores and/or to supply nutrients to her growing fetus.
But did you know fiber-digesting bacteria rely upon amylolytic, or starch- and sugar-digesting bacteria to complete proteolysis of rumen degradable protein (RDP) – the protein breakdown process to release peptides, amino acids and branched-chain amino acids (BCAAs). The same amylolytic bacteria then deaminate and decarboxylate (remove the amino and carboxyl groups) the BCAAs, releasing branched-chain volatile fatty acids. In other words, the rumen breaks down RDP through a complex process, eventually producing BCVFAs that are required by rumen bacteria for fiber digestion. BCVFAs are formed when the BCAAs (leucine, isoleucine and valine) contained in high RDP feedstuffs, such as soybean, rapeseed, cottonseed or sunflower meals, are degraded in the rumen. The BCVFAs are then utilized by both amylolytic and fiber-digesting bacteria to produce microbial protein.
BCVFAs act as carbon sources to be utilized with highly digestible protein (NPN) to produce the much-needed microbial protein and energy for production of milk by the mammary gland. When the cow produces higher levels of BCVFAs, both the fibrolytic and amylolytic bacteria respond by increasing digestion of both fibrous and non-fibrous carbohydrate feed components. This increases the microbial efficiency of producing energy and protein. This process is illustrated by the left-hand side of the rumen in Figure 1. Note, oftentimes this process will only partially meet the cow’s requirements for branched-chain volatile fatty acids.
DIETARY CONDITIONS AFFECTING BCVFA PRODUCTION
Under certain dietary conditions there may not be enough BCVFAs produced to meet the requirements of the rumen microbiome and specifically the fiber-digesting bacteria.
These dietary conditions can include:
• Lower protein diets, where RDP is limited and results in reduction of BCVFAs.
• Short chop length, wet ingredients and/or insufficient starch and sugar. These can all limit proteolysis due to low rumen residence time or a smaller microbial pool.
• Highly fermentable diets, which may create a large pool of starch and sugar digesters with the potential to outcompete fiber digesters for BCVFAs.
An insufficient supply of BCVFAs is problematic as fiber-digesting bacteria not only use BCVFAs to synthesize microbial protein but they are also key to the formation of branched-chain long-chain fatty acids utilized in their cellular membranes. These fatty acids help give the bacteria cellular fluidity and are essential to their survival within the harsh rumen environment.
Production of BCVFAs is an inefficient process as it requires a significant supply of expensive RDP and, when feed passage rates are high as often observed in high producing cows (with higher intake), much of the RDP is not available to the rumen bacteria to complete proteolysis due to shorter rumen residence time. Failure to provide an adequate supply of BCVFAs may reduce microbial protein yield and fiber digestion, since limiting the availability of BCVFAs will also limit the growth of the fiber digesters. This ultimately results in poor nitrogen efficiency, inadequate microbial protein production and poorer utilization of forage.
THE SOLUTION: DIRECT SUPPLEMENTATION WITH BCVFAs
Direct supplementation with BCVFAs using Zinpro® IsoFerm®, versus relying solely on RDP, is beneficial. Zinpro IsoFerm is a unique blend of BCVFAs proven to significantly enhance rumen function by directly feeding fiber-digesting microbes. Multiple studies have shown the positive benefits of supplementing lactating dairy cattle diets with BCVFAs. As shown on the right-hand side of the rumen in Figure: 1, Zinpro IsoFerm precisely feeds the fiber-digesting bacteria, skipping steps and making the proteolysis process more efficient, thereby increasing fiber digestibility. Doing so can help fill the gap of required nutrients that exists when dietary conditions limit the natural production of BCVFAs. To see how this process works, watch this video.
By directly fueling the rumen, it can result in an increase in energy corrected milk, a reduction in dry matter intake and feed efficiency gains. The improvement in feed efficiency enables cows to produce more with fewer inputs. Ultimately, this leads to better nutrient utilization, enhanced on-farm and environmental sustainability and greater profit potential. This improves the sustainability of producers’ operations, makes the most of the ration investment and supports cows to be more profitable and productive.
ZINPRO ISOFERM PROMOTES SUSTAINABLE PRACTICES
Dairy producers are already active leaders in dairy farming sustainability with practices like recycling water, applying manure as a natural fertilizer and feeding human-inedible byproducts, such as canola meal, distillers’ grains, soybean hulls, corn gluten feed and many others. Nutritionists should capitalize on the upcycled fiber feedstuffs they are already including in the ration by including Zinpro IsoFerm in diet formulations to focus on fiber digestion. Improved fiber digestion equates to greater feed efficiency (FE) and income over feed costs (IOFC) – key metrics to drive dairy farm profitability.
Peer-reviewed research has shown that adding BCVFAs to dairy diets increased fiber (NDF) digestion by more than 7.5%, conversion of ruminally-digested feed to microbial protein by more than 6.5% and production of microbial protein by almost 8.5%. With improved fiber digestion and protein utilization, lactating herds have seen decreased dry matter intake (DMI) by 2% and improved FE by 5.5%. What does this mean for producers?
• Research and real-world experiences show 4.3% more energy-corrected milk (ECM)
• Fewer feed inputs are required, which helps lower feed costs
• By utilizing Zinpro IsoFerm in diets, dairy producers can further profit from a sustainable practice – feeding human-inedible fiber – that’s already commonplace on their operation
Additionally, improvements in microbial protein yield may provide an opportunity to reduce dietary crude protein and more specifically rumen undegradable protein while maintaining performance.
BRINGING IT ALL TOGETHER
As an industry, we must focus on improving fiber digestibility as a key driver of feed efficiency, animal performance and producer profitability. Branched-chain volatile fatty acids (isoacids) play a critical role in improving the ability of rumen bacteria to effectively break down forages and human-inedible byproducts into useful nutrients for milk production. However, this is a complex process, and certain dietary conditions often make this process inefficient, limiting the cow’s ability to meet her BCVFA requirements.
With the emergence of new technology, nutritionists now have the ability to directly supplement BCVFAs when deficiencies are present, fully meeting the requirements for fiber digesting bacteria. This new tool, along with a focus on harvesting high quality forages, yields benefits for the cow, the producer and the environment.
About Dana Tomlinson, Ph.D.
Dr. Dana Tomlinson earned his doctoral degree in animal science and dairy management from Virginia Polytechnic Institute and State University. He serves as a dairy research nutritionist on the global technical services team for Zinpro IsoFerm, directing product research and technical support for global sales teams and customers
