Optimizing the use of exogenous enzymes in monogastric nutrition to reduce environmental impact
With the improvement of the standard of living of the population there is an increase not only in the demand for products of animal origin, but also an increased expectation that in addition to nutritious food should be safe, healthy and safeguard the environment. Animal production has evolved and continues to evolve greatly through the genetic improvement of animals, as well as improvements in nutrition, management and ambience. However, even in the face of improvements in productivity rates, consumers still question the sustainability of livestock production, and more recently we have seen an increase in alternatives to animal products in which they state to be more sustainable and as nutritious as animal products. It is then clear that animal production should take a proactive action in reducing the environmental impact caused by it and demonstrating the advances for public opinion.
Several countries, through the Paris agreement, set targets for reducing greenhouse gases. Although at this first moment the attention is not focused on agricultural activities, it is certain that over time we will have goals to be met since livestock production contributes for about 15% of the total greenhouse gases. It becomes important then to understand the factors that affect emissions in animal production, and in this context, we know that animal nutrition is the biggest contributor to emissions of livestock production.
To better understand the diet impact, imagine that when we use different ingredients in feed formulation, we do so to achieve ideal nutrient levels for their growth at a minimal possible cost (low cost feed formulation). From a sustainability point of view, when we use these ingredients, we assume the burden of the environmental impact caused by the production of these ingredients. We should then have in mind that the better use of these ingredients by animals will bring a reduction in environmental impact or greenhouse gas emissions. By using exogenous enzymes, such as phytase and xylanase, there is an improvement in the utilization of dietary nutrients, which in turn is an interesting strategy to reduce livestock production environmental impact.
The use of exogenous enzymes is something relatively recent in animal nutrition. The first commercially available enzymes were carbohydrases, which were introduced in the mid-1980s. Initially, the objective was to allow diet formulations with a greater inclusion of viscous grains such as barley and wheat, since these ingredients had a more affordable cost, but increased intestinal viscosity, bringing challenges to digestion. At the beginning of 90s, phytase became available, and sought to reduce the inclusion of phosphate in diets, reducing the cost of formulation whilst also reducing the amount of P excreted and the risk of P pollution and eutrophication.
Over the years, better knowledge of the anti-nutritional effects of substrates for exogenous enzymes, phytate in the case of phytase and arabino-xylans in the case of xylanase, allowed us to improve enzymes characteristics, and today we have available on the market more efficient enzymes. It is still quite common that we do not exploit the full potential of this technology, either by not optimizing the dosage of enzymes, or by employing conservative matrices thereby mitigating the risk of reduced performance of animals. It is known that both phytate and arabino-xylans are potent anti-nutrients, reducing the digestibility of minerals, amino acids and energy. In this sense, the greater the breakdown or hydrolysis of these compounds, the more efficient the animals will be in the use of nutrients contained in the different ingredients.
Thus, AB Vista sought to better analyze and understand the phytate and arabino-xylan content of the ingredients, aiming to optimize the use of enzymes. The knowledge acquired culminated in the generation of analytical services for the measurement of substrates via NIR technology, which allows us to make more accurate recommendations for the use of phytase especially, and to be able to better understand the challenges that be caused by soluble and insoluble arabino-xylans.
More recently, a series of 4 experiments were carried out involving broilers and pigs. The objective was to validate the usage of high doses of phytase in combination with xylanase (also called maximum matrix nutrition). A dosage of 2,000 FTU/kg of phytase was used in 3 of the 4 experiments, and 9,600 BXU/kg of xylanase. It was possible to reduce up to 150kcal/kg in the metabolizable energy of the diets, up to 0.22% in the amount of available P, in addition to the reduction of up to 0.05% in digestible lysine and other nutrients such as calcium, sodium, and other amino acids. Experimental design also considered diets without enzymes (positive control), diets containing conventional levels of enzymes applying a conservative nutritional matrix (industrial control), and a negative control, were nutrient reduction followed the aforementioned reductions, but without the inclusion of phytase and xylanase. Performance parameters were measured (weight gain and feed conversion), and additionally calculated the feeding cost and greenhouse gas emission (CO2e).
Animals fed negative control diets showed lower weight gain and higher feed conversion (Figure 1). The worsening of the performance of the animals caused the benefit in the cost of formulation to be lost, and the cost per kg of gain was similar to the animals fed the positive control diet, but with a significant increase in the emission of greenhouse gases (Figure 1). Animals fed industrial control diets presented similar performance to animals fed positive control, but with a reduction in feed cost and greenhouse gas emissions (Figure 1). The best results were observed in animals fed phytase at higher doses associated with xylanase, which were supplemented on top of negative control diet. It is evident the recovery of performance of animals at equivalent levels of positive control, with greater reduction in feed cost and lower emission of greenhouse gases than animals fed with the industrial control diet.
Figure 1 - Average performance, feeding cost and greenhouse gas emission of chickens and pigs fed different diets
The use of higher dosages of phytase combined with a regular dosage of xylanase allowed the reduction in feed cost without affecting the performance, thereby reducing the environmental impact of the production of chickens and pigs. It is possible in this way to optimize the potential of the use of exogenous enzymes, but it is important to analyze the diets for substrate content in order to make sure that enzymes could be releasing that amount of nutrients.
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