BRI BioResource : How to Improve Confidence in Enzyme Evaluation Trials

Part 1: The Impact of Feed Formulation on Trial Results

Comparing and evaluating enzyme feed additives is challenging. There are an increasing number of products available on the market, many of which have similar performance claims. In order to accurately identify the optimum enzyme choice for your situation, it is highly recommended that animal producers conduct field trials. However, these trials often fail to provide a conclusive answer for a variety of reasons. In some cases, the trial results may show little or no improvement at all, despite the manufacturer's claims. Why did the product not perform as expected and as promoted by the manufacturer? What truly happened? Rather than engaging in assessing blame with the product or with the trial, it can be useful to investigate the application in a systematic approach.

A good place to start is an evaluation of the formulation of the diet. To improve confidence in trials and to consistently have better, actionable results, the following three feed formulation factors should be considered:

1. Select a Feed Formula with Appropriate Substrate Content

Each class of enzymes has a specific substrate. For example, xylanase acts upon xylan, which is abundant in wheat, while mannanase acts upon mannan, which is more abundant in guar meal. Problems arise when an enzyme is used with feed ingredients that contain insufficient amounts of the substrate. Without sufficient substrate to act upon, there would be less than the expected benefits of the enzyme during the trial. Therefore, when evaluating an enzyme, it is critical to quantify substrate content in the feed ingredients being used and, in consultation with the supplier, calculate or select the optimal enzyme matrix value for the particular diet formulation.

2. Avoid Over-Formulation by Using the Right Matrix Value

There are numerous variables in feed. As a result, many animal feed producers and integrators tend to use a larger than necessary amount of nutrients in feed to insure sufficient nutrition, termed over-formulation. Use of the proper enzymes can allow the feed producers to balance their approach. Using a feed formulation with an optimal balance of nutrients that aligns with the nutritional requirements of the animal promotes health and growth and protects the bottom line of the company. While this is definitely easier to say than to do, enzymes can insure that nutrients are effectively utilized by the animal. Nutrients must be calculated as ratios of each other, such as the ratio of energy to crude protein. Each nutrient must be balanced in a way that allows the animal to efficiently utilize a nutrient in the presence of other nutrients - not too much, nor too little. Improper balance can lead to the excess of a specific nutrient, which would not be utilized and ultimately excreted as waste. Adding an enzyme to the diet affects nutrient digestibility, which alters the optimum nutrient balance of the diet. Therefore, it is critical to use the right enzyme matrix value in the feed formulation program in order to maintain the balance of nutrients.

Example

Energy is the most expensive nutrient in the diet. The addition of amylase, xylanase or protease enzymes to diets provides producers with an opportunity to reduce energy input due to increased energy provided by enzyme activity. However, the diet must be carefully calculated to maintain an appropriate balance of nutrients. For example, when using a xylanase enzyme to reduce the metabolizable energy (ME) required in poultry diets, the amount of energy or amino acids that would be released from the enzyme must be determined and included in the matrix to bring the ratio of energy to amino acids in the optimum range to meet poultry requirements. The figure below illustrates how the ratio of metabolizable energy to the amino acid lysine should be considered. In the standard diet, an optimal ratio (3050:1.25) is achieved. When reducing the ME (-130 kcal/kg in this example) according to the matrix value, the ratio of ME to lysine is no longer optimal (2920:1.25 in this example, assuming zero matrix value for lysine). Yet, when including the enzyme the optimal ME to lysine ratio is re-established (darker shade ME).

3. Consider Feed Ingredient Variation

Animal producers use ingredients that may originate from a variety of sources. Feed ingredients vary in nutrient content and digestibility according to their origin. Processing of ingredients, such as heat treatment, also impacts digestibility of nutrients. Low digestible ingredients and increased abundance of substrate increase the potential for enzymes to have a positive effect, whereas high digestible and low abundance of substrates diminish enzyme impact. In order to accurately formulate the diet to measure enzyme effect, each ingredient must be analyzed for its nutrient content and the feed analysis incorporated into formulation software.

Summary

A successful enzyme evaluation trial start depends upon selecting the right substrate-enzyme combination and using the right matrix value for each enzyme and ingredient to maintain balance nutrients. It is also important to take into consideration the variation among feed ingredients, as that greatly influences the effectiveness of a specific enzyme. A diet formulated with excess energy and insufficient amino acids or vice versa will lead to poor growth, which could be incorrectly attributed as an enzyme effect or an ineffective enzyme. Animal producers should consult with the enzyme manufacturer on the optimal matrix value when designing the evaluation trial to ensure the most accurate results.

Look for the second part of this blog series, which will address 'The Impact of Experiment Design on Trial Results'.

References

Gaëlle, B. 2013. Evaluating the efficacy of feed additives. In vivo nutrition et Santé animals, France Baéza Elisabeth at INRA.

Slominski, B. Recent advances in enzymes for poultry diets. Department of Animal Science, University of Manitoba Winnipeg, Manitoba, Canada.

About the author

Basheer Nusairat, associate nutritionist, earned his Ph.D. in 2014 from North Carolina State University where his work focused on altering the nutrition of broilers to improve efficiency and environmental sustainability by using low phytate varieties of soybean meal and enzymes that improve nutrient digestibility.