Vitamins & Un-Identified Growth Factors in Poultry Feeding (Basics)

VITAMINS:

  1. i) Fat-soluble vitamins (A, D, E & K).
  2. ii) Water soluble vitamins which include so-called B-complex vitamins and vitamin C (Ascorbic acid).

Vitamin C is synthesized by poultry and is accordingly not considered a dietary required nutrient. There is some evidence, nevertheless, of a favorable response to vitamin C supplementation by birds under stress.

The requirement for most vitamins is given in terms of mg/kg of diet. Exceptions are vitamins A, D, & E for which the requirement is commonly stated in units. Units are used to express the requirements for these vitamins because different forms of the vitamins have different biological activities.

            IU        = International Unit.

            ICU     = International chick unit.

            USP     = United States Pharmacopoeia.

Requirements for vitamin A are expressed in either IU or United States Pharmacopoeia/kg of diet. Requirements of poultry for vitamin D are expressed in ICU which is based on the activity of vitamin D3 from fish oils. They do not, however, use vitamin D2 from irradiated plant sterol as effectively as do rats or other mammals. The dietary requirements of vitamin D are highly variable and depend upon the concentration and type of fat in the diet, the concentration of selenium, and the presence of antioxidants.

Vitamin K activity is exhibited by a number of naturally occurring and synthetic compounds with varying solubility in fat and water. Menadione is a fat-soluble synthetic compound that can be considered as the reference standard for vitamin K activity. Two naturally occurring forms are K1 or phylloquinone and K2 or menaquinone. Water soluble forms include menadione sodium bisulfite (MSP) menadione sodium bisulfite complex (MSPC), and menadione dimethyl pyrimidol (MPP).

            Requirements for some of the vitamins may be met by the amounts occurring as natural components of the customary feedstuffs used in compounding diets. When the conventional feedstuffs are not available, however, the product used in substitution may not supply a sufficient amount of the various vitamins. Formulators of poultry feed should, therefore, be alert to the need for dietary supplementation with vitamins, usually assumed to be supplied by the feedstuffs.

            The requirements for water-soluble vitamins are interrelated in some instances. They are also dependent upon the nature of the diet. The type of carbohydrates, protein concentration, and amino acid balance are major factors determining the dietary requirements for several vitamins. 

UNIDENTIFIED FACTORS (UIF):

There are numerous reports of favorable responses to the dietary inclusion of natural products that have not been identified with any of the known nutrients. Stimulation of growth, increased egg production and hatchability, reduced liver fat, improved product quality, and reduced toxicity of minerals have been stated as evidence for the presence of unidentified factors in diverse products such as egg yolk, whey, yeast, fish, and meat by-products, soybeans, corn green forges, and fermentation by-products. Some responses, originally attributed to unidentified factors, have subsequently been shown to be the result of trace minerals. The complexity of optimum dietary balance among the minerals and the evidence for the essentiality of some of the newer trace elements suggest that components of natural products may directly or indirectly be factors associated with the mineral nutrition of poultry.