There are no major alternatives to corn and soybean meal on a worldwide basis, but when we move away from major corn-producing regions, such as the USA, Brazil and Argentina, the use of byproducts or alternative feed ingredients is gaining popularity. Especially in such cases, nutritionists face a tough challenge in maintaining animal performance and health while keeping feed costs at an economical level. With that in mind, now more than ever it is crucial that the issue of digestibility be addressed.
In his recent paper, titled “Future considerations in poultry nutrition,” Dr. Steve Leeson stated that corn and soybean meal will remain as the main staples of all poultry diets (Leeson, 2012). It is not too bold to say that this statement also holds true for swine nutrition. In spite of the ongoing debate pertaining to energy levels and nutrient density of diets in times of escalating feed prices, little debate is expected when one states that especially in such conditions, diet efficiency is of utmost importance.
Back to basics
Digestibility refers to the extent to which nutrients contained in a feedstuff are absorbed by the animal body as it passes through an animal’s digestive tract. Better digestibility of nutrients, or simply, better digestion, results in better feed efficiency. In animal nutrition, the use of enzymes aiming at increasing digestibility of nutrients is not a new topic and is a widely generalized practice.
In human nutrition, the use of herbs, spices and other plant-derived (phytogenic) substances in food is widespread, whether being for their flavoring, coloring, preservative, antimicrobial or digestive stimulant action, amongst others. Nowadays, several phytogenic feed additives are available and can be used in livestock diets. Some of these are tailor-made products, optimized to different animal species and production stages. They comprise high-quality herbs, spices and essential oils in standardized formulations that work together to increase digestibility, reduce intestinal inflammatory processes and stabilize intestinal health (Figure 1).
A commercially available phytogenic feed additive has been shown to improve apparent ileal digestibility of protein, fat and starch in piglets by 10, 8 and 1.4 percent, respectively (Maenner et al., 2011). Furthermore, it increased the digestibility of essential amino acids in a statistically significant manner (Figure 2).
With regard to poultry, and specifically for layers, diet composition may have a considerable impact on the nutrient content of eggs, especially that of fat-soluble vitamins (Naver, 1979). By monitoring vitamin content in eggs, we can ascertain the extent to which they are absorbed by the animal. Table 1 shows how the content of vitamin A, E and carotenoids (including provitamin A) in the egg yolk of layers was improved by supplementation with a phytogenic feed additive. This improvement was accompanied by greater protein, lysine, methionine and fat digestibility, a statistically significant increase in egg weight per egg (P≤0.05), and a better egg production rate, FCR and egg mass when in comparison with the control group (data not shown).
Digestibility: key for good performance
Widyaratne and Drew suggest that low-protein diets can support broiler growth performance equal to high-protein diets when highly digestible ingredients are used (Widyaratne and Drew, 2011). As prices of feed ingredients continue to rise, the use of bio-fuel byproducts, such as DDGS and other less-digestible commodities (vs. their corn and soybean meal counterparts) namely canola meal, meat-and-bone meal and lupines, also increases. Phytogenics have been proven to aid the digestive process thus increasing the amount of nutrients available for the animal.
Ultimately, as more nutrients are utilized by the animal, less will pass undigested. This results in less use of nutrients by pathogenic bacteria in the gut and in a reduction in their excretion of toxic metabolites. Table 2 shows how NH3 concentration in the air of a broiler house was reduced with the use of a phytogenic product. A fact accompanied by better feed efficiency and heavier birds (data not shown). Such data indicates that protein was better utilized by the animals leading to less nitrogen in excreta, and thus, a reduction in hazardous ammonia levels in the poultry shed.
While having a different mode of action, and even if they should not aim to replace enzymes in animal diets, phytogenic substances may have a complementary action in terms of digestibility of nutrients with supplementary benefits in terms of animal health. Ultimately, if we do it every day with our food, it seems unnecessary to doubt its benefits when applied to animals.