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Do phytases always work in poultry nutrition?

Published: September 14, 2017
By: Mahmoud Farahat, Ph.D. / Consulting Nutritionist - Zagazig University.
Some producers complain that their meat or egg type chickens suffer from problems in bone or egg shell quality when they include phytase in the diet as a partial substitute for the inorganic phosphorus sources (MCP; DCP; bone meal) according to the matrix value provided by the manufacturing company. Under field conditions, phytase activity is controlled by several parameters. This article will spot the light on utilization of phytase enzyme in poultry nutrition and the factors influencing its activity.
Phytate (phytic acid) compound is formed in the plant via phosphorylization of myoinositol to form myoinositol hexaphosphate (IP6). Plant based diets contain approximately 1% phytic acid and 0.28% phytate bound phosphorus. Phytic acid has several adverse effects on poultry nutrition (binding phosphorus and reducing its availability; forming insoluble complex with some cations such as calcium, zinc, iron and magnesium; lowering protein/amino acid digestibility due to forming insoluble complex with protein, increased endogenous losses, and inhibition of proteases; reducing energy digestibility due to increased endogenous losses, lowered fat digestion, and to a lesser extent inhibition of amylase enzyme).
Phytase enzyme (myo-inositol hexaphosphate phosphohydrolase) has become a common tool utilized by poultry nutritionists to lower feed costs, reduce the negative impacts of phytic acid on the nutrient digestibility and environment. Fytase units (FTU) is used for measuring phytase enzyme activity; one FTU unit is defined as the amount of enzyme that required to liberate 1 µMol of inorganic phosphorus per minute from 5.1 mMol/L sodium phytate at 37º C and pH 5.5.
Phytase starts release of phosphorus atoms from phytic acid by hydrolysis of fully phosphorylated phytate compound (IP6) to less phosphorylated compounds (myoinositol penta phosphate (IP5), myoinositol tetra phosphate (IP4) and myoinositol tri phosphate (IP3). Under in vivo conditions, the hydrolysis does not continue to yield myoinositol di phosphate (IP2), myoinositol mono phosphate (IP1) and myoinositol.  The capacity of IP6 to bind protein and minerals in the digestive tract is much higher than that of IP5, and that of IP5 is much higher than that of IP4 and IP3. For instance, the binding capacity of IP3 to calcium is only 11% of that of IP6.  Therefore, it is important that most of IP6 and IP5 been hydrolyzed in the upper digestive tract as complete as possible to reduce calcium binding in the intestine. On average, phytases degrades 35% to 50% of feed phytic acid.
Phytases can be classified according to the initial site of phytate hydrolysis in myoinositol hexaphosphate ring into 3-phytase or 6- phytase. The 3-phytases liberate P moiety at position C(IP3), while the 6-phytases liberate P moiety at position C(IP6). Phytases can also be classified according to their origin into fungal and bacterial phytases. Fungal phytases are either derived from Aspergillus niger (3-phytase) or from Peniophora lycii (6 phytase). Bacterial phytases are derived from E.coli, Citrobacter braakii or Buttiauxella spp, and all considered 6-phytases.

Examples of some commercial phytase products
Do phytases always work in poultry nutrition? - Image 1

Factors affecting phytase activity
1) pH
pH of 2.5 to 5.5 is the optimum range at which maximum benefits are obtained from phytase. Research studies revealed that bacterial phytase is more effective than fungal phytase at the above mentioned pH range.
2) Resistance to endogenous protease
Phytase enzyme is a proteinaceous compound, so, it can be susceptible to hydrolysis by pepsin enzyme in the GIT. Bacterial phytases revealed higher resistant against hydrolysis than fungal phytases.
3) Resistance to temperature
Due to its protein nature, phytase enzyme can be inactivated if exposed to a high temperature (above 70-75 ° C) as that occurs during feed conditioning and pelletizing. If the temperature exceeds 80 ° C as that occur during feed pelletizing, phytase enzyme should be protected either by coating or by providing it in an intrinsically thermostable form. Unprotected phytases can be utilized in pelletized feed in liquid form via spraying on the feed post pelleting.
4) Dietary Factors
a) Mineral content
Although doubted in some literature, high level of dietary calcium has been reported to adversely affect phytase efficacy either via complexing with phytic acid in the small intestine and forming an insoluble complex or via binding to the active site of phytase enzyme. Similarly, higher levels of iron or zinc make insoluble complex with phytate and subsequently decrease the phosphorus releasing efficacy of phytase. Recently, high dietary sodium has been revealed to decrease phytase activity. Inspection of the mineral content of farm drinking water should be conducted at least once per year as most water of desert areas contains very high level of some minerals that could hinder phytase activity. Phytases that efficiently hydrolyze phytate in the proximal gut (crop and proventriculus) will counteract the adverse effect of high dietary minerals.
b) Dietary phytate level
Although phytase activity (phytate hydrolysis) is increased in diets containing low level of phytic acid, the absolute amount of liberated phosphorus is high in diets containing high level of phytic acid compared to those with low phytic acid. The degree of phytate hydrolysis and phosphorus release was at its highest level in rice polish followed by rice bran, wheat bran, sunflower meal, wheat middling, canola meal, soybean meal, corn gluten meal, full fat soy, wheat, corn, barley, sorghum, and corn DDGS respectively.
c) Feed acidification
As the acidic pH is the optimum pH for phytase activity, adding organic acids in the feed such as citric acid has been reported to increase phytase activity.

Phytase matrix value
Although each phytase product has its own matrix value that published by the manufacturing company, these matrices are not derived in the same way. The matrix involves values for Av. phosphorus, calcium, protein/amino acids, energy, and sodium. Research results and field experiences revealed that there should not be a fixed matrix value for phytase in all feed formulations. Poultry nutritionists can have their own matrix values that can be more reserved and have more safety margin than the values published by the manufacturing companies.

Conclusion
To get maximum benefits from phytase inclusion, phytase enzyme should be characterized by having a maximum activity at a pH range of 2.5 to 5.5, hydrolyzing most phytate esters (IP6 and IP5) to at least IP4 in the upper part of the digestive tract as quickly as possible, resistant to endogenous proteases and heat stable. Properly acting phytase will reduce feed costs, improve efficiency of phytate phosphorus and other nutrient releases, and protect the environment from phosphorus pollution.
References
  1. Dersjant-Li, Y., Awati, A., Schulze, H. and Partridge, G. 2015. Phytase in non-ruminant animal nutrition: a critical review on phytase activities in the gastrointestinal tract and influencing factors. J Sci Food Agric. 95: 878–896.
  2. Selle, P.H. and Ravindran, V. 2007. Microbial phytase in poultry nutrition. Anim. Feed Sci. Technol. 135: 1-41.
  3. Web search in phytase producing companies
  4. Field experience

Related topics
Authors:
Mahmoud Farahat
Olam Group
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Sachin Patil
Huvepharma
14 de octubre de 2017

Really very informative data shared.
I would like to add some points about Ideal Phytase
Based on PPS
P-pH profile
Important to be highly effective in low pH.
Important to be effective at broad range of pH (1-5) range
P-Pepsin
Pepsin Resistant
Important to be resistance to pepsin to avoid the loss of activity in vivo.
S-Speed
Important to have fast working phytase because feed passage time in proximal gut is very less, so to release more and more phytate with the high speed.
Regards,
Dr Sachin Patil,India
M.V.Sc

Haroon Mushtaq
12 de octubre de 2017
If phytase is intrinsically heat stable, then there is no question that it wouldn't work, however question is that what is maximum threshold of this temperature for each of fungal or bacterial phytase??? Moreover, what is digestibility coefficient of each of the ingredient against such phytases, is it same or different??? At the end sometimes it is speculated if only phytase is the reason of lameness in Broilers???? Means AvP from the ingredients isn't sufficient to protect birds from lameness at least???? OR birds use AvP to protect themselves from lameness only......
Youssef Attia
11 de octubre de 2017

It works very well, depends on many factors of which the dose and type of phytase and Ca and Phosphorus and Ca/ P ratio

Aaron Cowieson
dsm-firmenich
4 de octubre de 2017

Just reacting to the original question (do phytases always work in poultry nutrition). Clearly this depends on how you define 'work' i.e. what the expectations you have of the phytase. It would be possible, for example, to manufacture a situation where the efficacy of the added phytase looked very poor e.g. if the diet to which you add the phytase has a high concentration of digestible phosphorus (above the animals requirement), or a very low concentration of phytic acid, or has a digestible SAA limit or where the phytase has been added inappropriately (perhaps a heat labile product was added pre-pelleting and the conditioner temperature, steam pressure and residence time were high) etc. However, when high quality phytase products (gastric stable, appropriate pH range, stable product form, good particle size and distribution through the feed etc) are added with the appropriate adjustments to diet composition (including Ca and P in particular) I think we can safely say that yes, phytases always work in poultry nutrition. In fact, phytases save the global feed industry in the region of $5-6bn per annum through reducing nutritional input costs, not to mention the added benefits on animal performance and environmental sustainability.

Steffen Hansen
PIG.dk
24 de septiembre de 2017
Apart from the above points you can also add that simple human errors during feed mixing can influence the expected content of phytase. Too much confidence in the mixing equipment may also cause unexpected phytase levels in the final feed. Incorrect storage of the phytase product may also lower the expected phytase activity in the final feed. The phytase products´ particle size and particle size distribution may influence the homogeneity of the distribution of phytase in the final feed.
Dr Piotr Stanislawski
dsm-firmenich
19 de septiembre de 2017
Excellent article,covering in quite simply way all aspects of phytates /phytase /phosphorus. I like it very much. Just some additional words. 1.phytase unit: there is more than one unit name and value.The registration conditions (eg.pH 5,5, temp 37C, 1 min....) are same but other factors (the buffer, colorant, etc in lab conditions) are different. Eg.one unit FTU (Du Pont) is not equall to FYT (DSM). All companies/producers have own system/method to describe 1 unit. 2.The hydrolysis of IP6,IP5, IP4 depend on the speed; we (birds) have short time in low pH (proximal gut) to work efficiently and hydrolyse as much as possible higher esters (IP6,IP5,IP4). Adding more proper phytase (higher dose per t feed) we influence the speed and the final result. Lower esters (IP3,IP2, IP1) are not as bad (as antinutrients) as the higher ones (as you wrote above) and could be hydrolysed by internal enzymes. Finally we got pure myoinositol- a "factor" improving weight gain and FCR. The "speed" of degradation the higher esters is different for various phytases. 3.the matrix: should be different for various species, age, dose (response is not linear). Good/serious companies based the matrix values on many scientific trials and research,but we see sometimes a matrix values taken "from the roof". Then we could meet problems on a farm- deficiency in macrominerals and ME (as the main values saving fed cost). The conclusion- I like yours. Thanks Mahmoud.
Zeeshan Ahmad
13 de octubre de 2017
Respected Aaron Cowieson, You have mentioned about particle size of Phytase among other features. Could you please briefly describe it and also advise what is ideal particle size of Phytase?
Ang Lee
New Hope Group
11 de octubre de 2017
How to treat phytase 5000 and phytase 10,000? which one is better ? why ?
Joseph Akayi Nammonywa
9 de octubre de 2017
Phytase works very well when correct FTU matrics are applied in the formulations.
Ken Ken
Sanimals
8 de octubre de 2017
The phytase normally works very well. The problem had experience for some products required to use 750 ftu per gram (not 500 ftu/g like some products) and cannot use double dose. Some problems from the stability of products and the coating technique should be concerned.
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