Most poultry diets around the world consist of about 70% corn or wheat, 20% soybean meal, and 10% other ingredients such as minerals, vitamins, and additives. Clearly, this is an oversimplified model, as there is a whole science behind feed formulation with countless ingredients and dietary specifications. However, this "model" feed formula provides a simple visual aid to show that most poultry meat and eggs are produced using a fairly limited number of major ingredients.
The three most expensive nutrients in animal feed, in absolute terms, are energy, protein, and phosphorus. Animals obtain these nutrients from feed through a process of digestion, whereby they secrete endogenous enzymes and then absorb these nutrients from the gastrointestinal tract. Increasing the digestibility of these nutrients is the most obvious way to increase the net gain that animals obtain from their feed. One method of achieving this goal is by using feed additives such as poultry enzymes. In most cases, this has been shown to be beneficial, increasing feed efficiency by around 5%.
Grains and protein sources such as soybean meal contain a lot of fiber, including mostly indigestible non-starch polysaccharides (NSP). In fact, a typical diet contains about 13% fiber material, which is simply excreted in the environment, although some limited fermentations occur in the large intestine. The most easily attacked fiber by poultry enzymes is NSP, as cellulose and pectin/gum appear to be resistant to existing commercial enzymes. Thus, increasing the digestibility of NSP has been shown to provide additional energy to poultry, about 50 kcal ME/kg feed, representing 2-3% of the total diet ME concentration.
However, NSP enzymes in poultry can also release potentially concentrated protein and minerals, which are often associated or trapped with NSP molecules, bringing further benefits. One obvious but often overlooked effect in poultry is that NSP enzymes usually reduce intestinal viscosity (most NSP are essentially "viscous" extracts), which has been shown to improve overall litter quality for birds raised on the floor, including reducing the incidence of "dirty" eggs. The only problem with NSP enzymes is that natural sources usually have a low concentration of NSP (for many good reasons). In these cases, the use of NSP enzymes may appear to be a waste of money on a seemingly ineffective additive.
Preliminary contrast assays and further commercial tests have demonstrated that, taking into account the cost of the enzyme, some protease enzyme powder can decrease feed costs by about 2-5%, or increase broiler performance by as much as 4-6% in diets with imbalanced protein content. Today, the supply of protein sources is abundant, and the use of protease enzymes still depends on the pricing of commercial protein commodities. Perhaps improved proteases will offer more significant benefits, which will make them more powerful in low-cost pricing of protein products.
Phosphorus digestion has great activity, and several successful phosphorus enzymes (phytases) have been produced and sold for quite some time. In short, phytase degrades phytate salts (an indigestible form of phosphorus) from plant sources. It can increase phosphorus digestibility by about 10%, and since calcium is also bound in the same phytate molecule, it can also increase calcium digestibility by about 10-20%. Limited and often-controversial research also suggests it may increase the digestibility of other nutrients bound to phytate salts, such as protein and trace minerals. Of course, the ultimate result of phytase is a reduction in excreted phosphorus, which can reach 30%. Recently, as most inorganic phosphorus sources (e.g., monocalcium phosphate and dicalcium phosphate) routinely added to most animal diets have become so expensive, the use of phytase enzymes provides users with huge economic incentives.
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