Phytic acid and its utilization by vitamin D3, Calcium, Phosphorous

 Phytic acid and its utilization by vitamin D3, Calcium, Phosphorous

-Eishika Das

Introduction:

•  Phytic acid (myo-inositol 1,2,3,4,5,6-hexakis dihydrogen phosphate), an organic phosphate, is a phosphorylated cyclic sugar alcohol (Figure 1). The anion form of phytic acid, phytate, is the form present in all plants. Phytate in plants is usually chelated with cations, proteins and/or starches and this chelated form is called phytin . Plant roots contain low amounts of phytin, and the compound is present, if at all, only in trace amounts in the vegetative parts of plants such as the leaves.

 In mature seeds, phytic acid is present as a complex salt of calcium (Ca), magnesium (Mg), potassium and possibly protein and starch and this complexed or chelated molecule is known as Phytin (Figure 2).

Location & composition:  

• The presence of phytin within seeds differs among different plants. 90% of the phytin in corn is found in the germ portion of the kernel, while in wheat and rice most of the phytin is in the aleurone layers of the kernel and the outer bran. In most oilseeds and grain legumes, the phytin is associated with protein and concentrated within sub cellular inclusions called globoids that are distributed throughout the kernel; however, in soybean seeds, there appears to be no specific location for phytin.
•  Phytic acid constitutes between 1% and 3% by weight of many of the cereals and oilseeds used in animal feeds. In mature seeds, phytic acid is present as a complex salt of calcium (Ca), magnesium (Mg), potassium (K) and possibly protein and starch and this complexed or chelated molecule is known as phytin.

Dietary Calcium and Phosphorus Utilization of phytate phosphorous in poultry is influenced by both calcium and phosphorous concentration.

The effect of dietary calcium is much greater. At very high level of calcium concentration phytate hydrolysis is completely prevented. That is the availability of phytate phosphorus decrease with increasing calcium content. At high level in layer feed about 4% calcium, phytate phosphorous is considered virtually unavailable.

A calcium: phosphorous ratio of 2:1 impairs the digestion of phytate because of the formation of an insoluble calcium phytate complex in intestine. Layer birds fed on a diet with calcium: total phosphorus ratio of 1:1 prefer better than those fed on a diet where the ratio 2:1. The effect of high levels of Ca on intestinal pH may be partly responsible for some of the deleterious effects that high dietary Ca levels have on PHYTIN-P hydrolysis. The size of the soluble mineral complexes

also influences the availability of PHYTIN-P and chelated minerals for absorption. The smaller the size of the phytin-mineral complex the greater the surface area available for the enzyme to attack so the complex would more easily be broken down.

Dietary Vitamin D3 level PHYTIN-P utilization decrease when diets are deficient of vit. D3. (Figure 3)

Addition of Vitamin D3 greatly increase the amount of PHYTIN-P utilization. This improve may be due to:

a) Increase synthesis or activity of intestinal phytase,

b) Increase phytate hydrolysis by stimulation of calcium absorption & calcium utilization. This makes phytate more soluble and available for utilization,

c) Increase absorption & utilization of phosphorous.

Figure : 3

Sources of Phytase Found In the GIT There are four possible sources of phytase which could be found in the GIT of animals:

a) Phytase present in feed ingredients,

b) Exogenous microbial phytase added to the diet,

c) Phytase produced by endogenous microflora in the GIT and

d) membrane-bound phytase in the intestinal mucosa Phytase present in the feed ingredients themselves has been shown to improve PHYTIN-P utilization by monogastric animals.

High levels of plant phytase are found in wheat, rye, their hybrid triticale and barley, yet there is a large variation in phytase activity within the different varieties of these plants. The pH and temperatures that occur during feed processing as well as the low pH in the upper portion of the GIT may inactivate the enzyme.