Effect of phytase on protein and amino acid digestibility and energy utilisation

Abstract

Phytate is a molecule rich in phosphorus (P). However, the P in phytate is of low availability to monogastric animals because they lack the proper enzyme system to hydrolyse phytate. Consequently, there is a high P concentration in the manure from animals fed on diets containing phytate, and this can lead to pollution of the environment. Because phytate can complex with minerals, starch, proteins and digestive enzymes, it also has anti-nutritional properties. Limiting the P output by monogastric animals, by increasing the digestibility (availability) of the P in the diet by hydrolysing phosphate from phytate, was the original reason for developing the microbial phytase, Natuphos®. It has been shown in many studies that P excretion by pigs and poultry can be reduced by 30% by including phytase in their diets. The digestibility of other nutrients bound to phytate can also be increased considerably by hydrolysis of the phytate molecule by phytase. A number of studies have been performed in poultry and pigs to determine the effect on amino acid digestibility of adding microbial phytase to the feed. In general, an increase of 1–3% has been reported. It was shown by meta-analysis that these improvements were significant for most amino acids at a phytase supplementation rate of 500 FTU/kg diet. In piglets and broilers an improvement in performance of 1.5-3.0% was often observed when phytase was included in the diet, even if the diet met the digestible/available P requirement. This improvement in performance cannot be explained by improvements in amino acid digestibility alone. It has been suggested that there is an effect on energy utilisation as well, and this has now been confirmed in studies with poultry. To apply this information in feed compounding, matrix values are proposed for use by the industry in linear programming. Depending on many factors, feed costs can be decreased by up to EUR 3.50 (US$ 3.00)/tonne by the addition of phytase to diets that are not limiting in P. Limiting the total P content in the diet to a lower concentration can increase the economic advantage of adding phytase. Processing of feed, especially pelleting, can reduce the activity of phytase. It is therefore necessary to protect the enzyme and this can be very difficult, especially when it is important that the enzyme should also become rapidly available to the animal. The product Natuphos® 10000 G fulfils these requirements. The broadness of the impact of this enzyme on the nutritional value of feed makes it a really remarkable enzyme.

Keywords::

• Amino acids
• digestibility
• energy
• environment
• phosphorus
• phytase
• pigs
• poultry