Introduction
Phytate:
The latter part of the past century witnessed drastic increases in the size of poultry facilities for better efficiencies and lower production cost. Concurrently, fast-growing, or high producing breeds of poultry were developed and raised to utilize a plant-based feeds in their ration. But one of the major drawbacks of this ration is that it contains high phytate concentration making phosphorus unavailable to poultry, thus increasing the amount of inorganic phosphorus in poultry diet. The unutilized feed phytate was largely excreted by these simple stomached species and rendered phosphorus in their excreta too high to be applied to cropland. The other menace phosphorus rich excreta pose is eutrophication.
Phytate: An Antinutritional Factor
Phytate is a polyanionic molecule with the potential to chelate positively charged nutrients, which is almost certainly fundamental to the anti-nutritive properties of phytate.
Impact of Phytate on
a. Feed cost : Phytates present in grains influences feed cost, because of which more exogenous P is required in feed. Generally, nutritionist tend to keep excessive P levels into normal poultry diet to guarantee a safety margin. Thus, it leads to increase in feed cost.
b. Effect on birds performance : Phytate has also been identified as an anti-nutritional factor. It can bind with other minerals, protein and starch, preventing their absorption in the digestive tract and make them unavailable to the birds.
c. Impact of phytate on protein/ amino acid availability : Protein-phytate complexes may be present in plant feedstuffs, but mostly such complexes are formed in the gastrointestinal tract. These complexes, has a negative influence on protein availability, which could occur in several ways. The consequences of which is low protein and amino acid availability.
d. Phytate interaction with digestive enzymes : Phytate is known to inhibit a number of digestive enzymes such as pepsin, β-amylase and trypsin.
e. Impact of phytate on mineral availability : The structure of phytic acid is indicative of its strong chelating potential. Phytate is a strong acid and forms a wide variety of insoluble salts with divalent or trivalent cations at lower pH, potentially rendering these elements unavailable for absorption.
Degradation of Phytic Acid:
Degradation of phytic acid may occur by hydrolytic splitting of the ester bond of phytic acid through various processing effects and/or by phytase, either from animal, plant or microbial sources.
Factor Affecting Utilisation of Phytate Phosphorus
Phosphorus is a very expensive mineral in poultry diet. The availability of phosphorus in plant feedstuffs varies from zero to more than 50%. It has been reported that the hydrolysis of phytate ranges from 3 to 42%. Poor utilisation of phosphorus not only results in higher cost of production, but also leads to environmental pollution. There are many factors which affect efficient utilisation and phytate bound phosphorus in poultry diets.
a. Genotype of bird :
The average retention of phytate phosphorus by Leghorn chickens is greater than by meat type broilers
b. Age of bird :
Phytase activity in gastro intestinal tract increases with age.
c. Dietary calcium level :
Calcium forms a precipitate with phytate in the gastrointestinal tract very easily due to its high concentration in ordinary diets. Therefore, phytate hydrolysis is inversely related to dietary calcium levels.
d. Dietary vitamin D3 :
Phytate phosphorus utilisation is improved in response to vitamin D3 supplementation and may be attributed to one or more of the following three mechanisms:
(1) increased synthesis or activity of intestinal phytase
(2) increased phytate hydrolysis
(3) enhanced absorption of phosphorus.
e. Dietary fibre content :
The cation exchange properties of dietary fibre in the diet may reduce the effective concentration of cations in the gastrointestinal tract, increasing phytate hydrolysis.
f. Type of feed ingredients :
The source of phytate can influence the availability of phytate phosphorus. Susceptibility of phytate from different feed ingredients to phytase activity is variable. This may be due to solubility at acidic pH, as soluble phytate will be more readily hydrolysed by phytase.
Phytase Enzyme
Phytase is an enzyme which hydrolyses phytic acid to inositol and inorganic phosphorus, leading to improved phosphorus utilisation and overall performance of broilers.
Characteristics of Phytase :
The Nomenclature Committee of International Union of Biochemistry (1979) lists two phytase :
(1) 3-phytase (Enzyme Classification 3.1.3.8.)
(2) 6-phytase (Enzyme Classification 3.1.3.26):
It is said that 6-phytase is better than 3-phytase, because 6- phytase will dephosphorylate a phytic acid molecule completely, whereas a 3-phytase may leave the job unfinished, leaving at least one unit of phosphorus unreleased.
WHY ADPHOS?
is a highly efficient 6-phytase derived from E.coli. ADPHOS has high affinity towards phytate, ensuring that even in diets with low phytate levels, it works with full efficacy to release nutrients that would otherwise be chelated by phytate.
Benefits of ADPHOS
ADPHOS increases bioavailability of phosphorus, calcium and amino acids.
a. Growth performance :
Supplementation of ADPHOS in poultry feed has been shown to increase body weight gain, feed intake and feed efficiency in broiler chickens, this is due to increase in availability of all nutrients which are bound to phytic acids.
b. Availability of protein and amino acids :
ADPHOS degrades phytate and is able to release phytate-bound protein. This leads to enhanced protein availability improved nitrogen retention. The magnitude of response to ADPHOS is greater in ingredients containing high level of phytate. It has been reported that poorly digestible feedstuffs are more responsive to ADPHOS than those with higher inherent digestibility. The source and chemical properties of both phytate and protein also contribute to the variability of protein and amino acid digestibility.
c. Energy utilisation :
ADPHOS has a positive effect on energy parameters. Improvement in protein/amino acid digestibility in poultry diets with added ADPHOS would be expected to result in improved energy utilisation.
d. Phosphorus and calcium availability :
Calcium retention increased linearly with increasing levels of supplemental phytase and decreased as the Ca:P ratio of the diet becomes wider and as the level of non-phytate phosphorus is increased.
e. Availability of other minerals :
Phytic acid chelates with cations (Ca, Mg, Zn, Mn and Cu), rendering them unavailable. ADPHOS, hydrolysed this phytic acid and releases the bound minerals.
f. Control in environmental pollution :
Poultry manure is becoming a major burden on the environment. Poultry manure is rich in phosphorus and is one of the major sources of phosphorus runoff leading to eutrophication. Eutrophication results in proliferation of algae and some aquatic weeds, thus harming fish and other aquatic life.
ADPHOS and its Economics
By using ADPHOS 5 & ADPHOS 10, we can replace up to 8 kg of DCP per tonn of feeds, which roughly come close to Rs 450/-.
Phytate- phosphorus contents of common feed ingredients (% DM basis)
(Source: Ravindran et al., 1994; Ravindran et al., 1995; Tyagi et al., 1998; Selle et al., 2000)
