Increasing the digestive efficiency of local raw materials with enzymes

Introduction

Global demand for animal protein is increasing. This is fuelling a high demand for animal feed. Feed costs are also high due to a combination of high energy costs, competition between food and feed markets and issues with ingredient availability and supply.

In this environment, pork producers (like other meat producers) are having to reconsider how to use available feed resources in the most efficient and effective way to maintain the cost-benefit of production. Alongside this, they are also having to consider sustainability indicators and make decisions about how to reduce emissions and waste whilst maintaining growth performance.

These two factors of efficiency and sustainability are driving a growing interest in the use of alternatives to conventional raw materials in swine diets.

This article explores current thinking in this area and the science of how enzymes can be used to improve feed efficiency and sustainability in diets containing alternatives.

What do we mean by ‘alternatives’?

‘Alternatives’ refers to new sources of energy, protein or other essential nutrients that can help to reduce the dependency on conventional grains and oilseeds. They include:

• by-products from the food industry (food waste, spent brewers’ grains)
• algae (microalgae, spirulina and chlorella)
• insects (black soldier fly larvae and crickets)
• alternative oils (coconut oil, palm kernel oil)
• non-conventional grains (barley 6C, corn gluten meal, wheat middlings, wheat hybrids)

An alternative may also simply be a local feed ingredient that is available in one market or region but not another. For example, locally available processed raw materials and co-products such as rapeseed meal, sunflower meal, wheat middlings and distillers’ dried grains with solubles (DDGS).

Evaluating the nutritional value of an alternative is key

Prior to inclusion in a new feed formulation, an alternative raw material must be evaluated for its:

• nutritional value
• safety
• palatability
• processing quality
• economic feasibility
• environmental impact
• availability

Assessing nutritional value is key because most processed raw materials and co-products contain higher levels of the antinutrient phytate, fibre and indigestible protein than the parent grain or oilseed.

The increased fiber content of processed raw materials and co-products is illustrated in Figure 1.

The higher fibre content of co-products compared with the parent grain/oilseed directly can directly impact on the digestibility of the diet in vivo. For example, in studies in nursery and growing pigs, total tract digestibility of dry matter, gross energy and crude protein was reduced by >5% in diets containing 25% canola meal or 30% DDGS (vs. 0%)^3,4.

How can enzymes help?

Clearly, the concept of using exogenous enzymes to improve feed digestibility by breaking down target substrates into simpler, more absorbable, forms is not new. What is new is the strategy of using enzymes to support increased inclusion of alternative ingredients in a more precision nutrition-based approach.

In this context, enzymes can:

• enable the use of cheaper and/or more locally available ingredients at a higher inclusion rate in the diet, without compromising on production outcomes
• reduce reliance on food-grade ingredients through increased use of co-products that supports the concept of a circular economy² in which losses are minimized and sustainability is improved
• compensate for variation in ingredient quality by adjusting the enzyme dose

NIR analytical technologies

Near-infrared (NIR) spectroscopy technologies can be particularly useful in this sphere.

At dsm-firmenich, NIR analytics are being used to rapidly and accurately assess the detailed nutritional composition of alternative (and conventional) ingredients. The technology allows quantification of a broader range of nutritional analytes than traditional methods, including phytate-phosphorus, total, soluble and insoluble dietary fibre, individual non-starch polysaccharides (NSP), resistant, readily and slowly digestible starch and indigestible protein and amino acids. It also enables variability in composition to be quantified.

Outputs can be used to map the availability of specific substrates (phytate, carbohydrates, protein, amino acids) against available enzymes (phytases, carbohydrases and protease) and to optimize the feed formulation accordingly.

Digestibility improvement factors (DIF)

As part of this work, dsm-firmenich has founded the concept of digestibility improvement factors (DIF) to refer to the (quantifiable) increase in nutrient utilization by the animal that is expected from the addition of specified enzymes at specified dose levels in a diet of known composition.

The DIF takes account of the enzyme’s precise effect on individual raw materials and their particular composition and substrate characteristics (e.g. the content of NSP arabinoxylans in a particular variety of wheat). Hence, this approach differs fundamentally from the ‘on top’ approach of using enzymes in feed, which confers a much more uncertain response. Work is ongoing to develop the supporting algorithms for using DIF to optimizing fibre digestibility in enzyme-supplemented diets.

Optimising amino acid and protein digestibility in diets containing soybean alternatives

With soybean prices continually increasing, producers are looking to incorporate alternative protein-sources into swine diets. Among the main alternatives are rapeseed meal and sunflower meal.

These are rich in protein but also less digestible than soybean meal. NIR analysis shows they contain:

• more fibre/NSP
• different types of NSP
• a portion of nitrogen trapped in the fibre fraction (neutral detergent fibre)
• more cellulose and pectin; addition of 5–7% rapeseed and sunflower meal as a replacement for soybean in piglet diets increases the pectin content by 30–50% and cellulose content by 10–20%.

In diets containing these alternatives, a different suite of enzymes is needed to maximize digestibility and maintain the nutritional value of the diet.

This may include xylo-glucanases to breakdown the xyloglucan (NSP) network, pectinases to break down the pectic polymer matrix and cellulase to break down cellulose in the cell walls.

Research at dsm-firmenich in growing pigs has shown that the combination of pectinase, cellulases and hemicellulases present in Ronozyme® VP improved protein availability and thereby increased daily gain and feed conversion ratio when added to diets containing 14 or 18% of rapeseed meal, to levels comparable to a conventional diet containing 11% soybean meal.⁵

What about sustainability?

Finally, the use of enzymes in swine diets containing alternatives can improve the sustainability of production. This is evident from numerous studies showing the environmental impact of added enzymes is small compared to the feed component that they replace⁶.

In this context it is clear enzymes can contribute to reducing both the carbon footprint of the feed (by enabling lower inclusion of raw materials or replacement with (local) alternatives) and that of the animal during growth (by increasing feed efficiency and reducing emissions). Quantifying these benefits and developing more sustainable diets with enzymes are major areas of future research.

Conclusions

Market pressures and an increasing interest in sustainability are driving pork producers to consider increased inclusion of (locally available) alternative raw materials in swine diets. This is fuelling science and research into how enzymes may be useful in improving the digestibility of such alternatives to maintain feed efficiency. At dsm-firmenich, a precision-nutrition based approach is being adopted that involves use of NIR analytics to understand the detailed composition (and variability) of alternatives and other ingredients in the diet, the mapping of available substrates to enzymes, and optimization of the diet formulation. This new way of using enzymes in diets containing alternatives is effective and can support both feed efficiency and sustainability goals.