Forage is the foundation of most beef cattle diets. Whether cattle are grazing pasture, eating hay or being fed silage, these feeds provide the bulk of nutrients for cow-calf, stocker and backgrounding operations.
However, many forages – especially mature grasses, drought-stressed pastures or crop residues – contain high levels of fiber that cattle cannot fully digest. As a result, some of the energy or nutrients locked inside this plant material passes through the animal unutilized.
In-feed enzymes are receiving increasing attention as a way to counter this significant and costly problem.
What are in-feed enzymes?
Enzymes are specialized proteins often added to livestock feed or supplements to enhance digestion, nutrient absorption and feed conversion efficiency. They work by breaking down complex, indigestible or antinutritional components and are typically produced through microbial fermentation using fungi or bacteria.
The most common enzymes used in beef cattle nutrition include:
- Cellulase and xylanase to help break down cellulose and hemicellulose in high-fiber diets; due to this function, these are called fibrolytic enzymes
- Amylase to aid in starch digestion; typically used in feedlot and dairy diets
Why fiber digestion matters in beef cattle
Most forages are made up largely of plant cell wall components, including cellulose and hemicellulose. These compounds are often referred to collectively as fiber. Because of their rumen microbes, cattle are more effective at digesting fiber than most other species. However, improving ruminal fiber digestion in higher-forage rations, even by a small amount, can have a major impact on both intake and performance.
Most feeds and forages have variable fiber content, and as grasses mature, fiber content also tends to increase, while digestibility and nutrient availability decrease.
This is where fibrolytic enzymes may help.
How enzymes improve forage utilization
Several university and commercial research studies have shown that enzyme supplementation increased the digestion of fiber components such as acid detergent fiber (ADF). In some cases, ADF digestibility improved by as much as 13%, depending on forage type.
Improved digestion was also associated with stronger rumen fermentation activity and better feed utilization. These overall improvements in dry matter digestibility, forage utilization, feed efficiency and performance might be attributed to:
- Increasing microbial access – By partially breaking down fiber, enzymes expose more surfaces where rumen bacteria can attach. This allows microbes to ferment the feed more efficiently.
- Improving energy availability – When fiber digestion improves, cattle produce more volatile fatty acids (VFAs) in the rumen – primarily acetate, propionate and butyrate. These compounds supply 60% to 80% of the animal’s usable energy.
When enzymes work best
Research suggests enzymes provide the most benefit in situations where fiber digestion is a limiting factor. These conditions often include:
- Mature or lower-quality pasture grasses
- Drought-stressed forage
- Crop residues such as cornstalks or wheat straw
- Poor-quality hay
- Backgrounding or stocker diets with high forage levels
In these systems, improving fiber digestion can increase the amount of energy cattle obtain from forage. However, fibrolytic enzymes generally show less consistent results in high-grain finishing diets (where fiber is a smaller portion of the ration). Here, amylolytic enzymes such as alpha-amylase, beta-amylase and glucoamylase, all of which target starch, might be a better fit.
Potential benefits for producers
When enzymes work effectively, producers may see several benefits, including:
- Improved fiber digestibility
- Better feed efficiency
- Increased average daily gain (ADG)
- Better use of low-quality forage
Perhaps the greatest potential benefit is improved utilization of lower-quality feeds. Enzymes may help producers make better use of crop residues, mature pasture or lower-grade hay during challenging forage conditions.
In-feed enzymes can be delivered to cattle in two ways:
- Mixed-in rations – Powdered or liquid enzymes can be added directly to grain supplements or total mixed rations (TMRs).
- Included-in supplements – Some commercial lick tubs, liquid feeds or mineral supplements include enzyme blends as part of their formulation or can be added upon request. Typical inclusion rates vary depending on the product but often range from 1 to 10 grams per head per day for concentrated enzyme products.
Factors affecting results
One challenge with enzyme supplementation is that results are not always consistent. Several factors can influence how well enzymes perform, including:
- Type and maturity of forage
- Enzyme formulation and activity level
- Method of application
- Rumen pH and microbial conditions
- Overall diet composition
Because of these variables, producers are encouraged to evaluate enzyme products carefully and ask for product-specific research.
The bottom line
Feed enzymes are not a silver bullet, but they can be a useful tool for improving forage utilization in certain beef production systems.
Research suggests that fibrolytic enzymes can enhance fiber digestion, increase rumen fermentation efficiency and improve feed utilization – particularly when cattle are consuming high-fiber or low-quality forages.
For producers feeding large amounts of roughage, especially in backgrounding or stocker operations, enzymes may help unlock additional energy from forage and improve overall feeding efficiency, thus minimizing feed cost and maximizing profitability.
