The importance of using the correct phytase at optimal dose
Phytate is a six-fold dihydrogen phosphate ester of inositol, specifically myo-inositol 1,2,3,4,5,6 -hexakiphosphate. Also known as phytic acid, it is considered the main storage form of phosphate in grains and plant sources1. However, phytate is not easily accessible to animals. Phosphorus (P) bound in this form has low availability and can negatively affect the digestibility of other nutrients and consequently animal performance2. It also has extensive and detrimental anti-nutritive properties which directly impact performance.
This is because phytate compromises nutrient availability and uptake by binding proteins and minerals, such as calcium (Ca)3, to form indigestible complex structures. In the small intestine, at low pH, this action reduces the absorption of vital nutrients in the feed and inhibits the enzymatic activity of trypsin and amylase4. While further down the digestive tract where pH levels are higher, it continues to bind to minerals and trace elements which can act as a bridge to further bind protein.
Undigested nutrients that reach the lower gastrointestinal tract (GIT) negatively affect the microbiota and ratios of microbial populations; increasing the presence of non-beneficial, opportunistic and potentially pathogenic bacteria - such as Clostridium perfringens, E. coli and Salmonella species - and leading to metabolic disorders or diseases.
All of these effects have damaging implications for animal growth, performance and welfare; where phytate reduces amino acid availability and digestibility, diverts energy away from growth, decreases bone mineralization by affecting the Ca-P balance, and increases phosphorous excretion.
The solution: Phytase
Phytase is one of the most commonly used enzymes in both poultry and swine feed, with recent surveys reporting significant dose increases in the diets. Its mode of action is a stepwise catalysis of the phosphorylated phytic acid or phytate (IP6) into its lower isomers in a descending order.
The faster and more complete the process, the higher the efficacy of the phytase and benefits to the animal. And it must happen in the upper gastrointestinal tract (GIT), specifically in the gizzard, proventriculus and crop within the low pH range of 2-4 that is seen in these organs.
However, it is important to recognize that a number of different factors affect the performance of phytase enzymes and should be taken into account in order to maximize results.
One of the most critical points is the optimal range of phytase activity. Current commercial phytases show significant variations in their efficacy at pH levels close to those in the upper GIT (Graphs 1 and 2); a difference that is particularly important given that the goal is to eliminate the detrimental effects of phytate and its associated anti-nutritive properties as early as possible.
The source and amount of phytate in feed ingredients is an equally important consideration. Notable differences in composition and levels in cereals can lead to major variations in terms the efficacy of the phytase used6.
Another key factor is Ca content and its ratio with P in the diet. Studies7,8 suggest that high levels of Ca in the diet can negatively impact phytase efficacy5, with a linear decrease in ileal phytate P digestibility from 4.7 to 11.6 g/kg reported. Whereas reducing ratio and Ca levels from 1:5 to 1:1 in pig diets, and from 2:1 to 1.2:1 in piglets10 has been shown to improve the efficacy of phytase in pigs.
Equally important is ensuring that the correct phytase is used at the optimal dose. In broilers, for example, studies have shown that increasing dose levels enhances results2, while the inclusion of up to 4,000 FTU of a consensus bacterial phytase variant improves the digestibility of P, amino acids (AA) and energy in a high phytate diet. Similarly, increasing dose levels from 250 to 1,000 FTU in pigs reportedly leads to significant improvements in performance.
This demands a detailed understanding of the highly influential role of matrix values, encompassing minerals (Ca, P, and Na), energy, and amino acids. The effective application of these values will not only maximize the benefits of phytase but also deliver a strong commercial return, with the majority of these savings attributed to improved energy contribution and reduced ingredient costs.
It also means that several factors must be taken into account when determining the optimal dose of phytase in the diet. The actual level of phytate is one of the most important. So too is analyzing calcium in terms of dietary content, solubility, and ratio to phosphorous. Calculations also need to be matched with the nutritional strategy of each individual operation.
In this context, Axtra® PHY GOLD - our novel phytase with superior bioefficacy - has been shown to deliver industry-leading results on every level. Firstly, in terms of speed and ability to break down phytate, it has been proven to reduce IP6 to lower isomers at low pH in the upper GIT and stomach faster than any other phytase currently available on the market. Indeed, performance can be further improved by using this science-based phytase in conjunction with proper non-starch polysaccharide (NSP) enzymes.
Secondly, Axtra® PHY GOLD directly addresses the need to consider and incorporate all three levels of matrix values - minerals, AAs and energy - into diet down-spec calculations. Its robust matrix values have been developed and tested in various animal trials, as well as proven in field studies and practice. For example, our research and field experience prove that the optimal dose is highly variable and needs to be based on a proper review and analysis of diets used and life cycle.
Given the far-reaching benefits of implementing an effective phytate reduction strategy - both in terms of animal performance and economic impact - selecting the correct phytase and optimal dose has never been more important.
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Article made possible through the contribution of Dr Amir E Ghane (PhD, PAS), IFF Danisco Animal Nutrition