Importance of Fat-Soluble Vitamins in Poultry Health and Nutrition

Vitamins are defined as a group of complex organic substances that are essential for normal metabolism and their deficiency in the diet causes disorders among animal species.

These essential nutrients can not be synthesized either at all or to some extent by the animal body. Therefore, it is important to ensure the availability of these micronutrients through diet according to the requirements to get optimum productivity, performance and overall health benefits.

Vitamins are of two types, fat-soluble vitamins and water-soluble vitamins. The vitamins A, D, E and K are fat-soluble whereas water-soluble vitamins are B vitamins and vitamin C.

Fat-soluble vitamins consist of carbon, hydrogen and oxygen only. On the other hand, water-soluble vitamins contain C, H, O, and N, S, Co, or P. The biological functions of each vitamin depend on its unique chemical nature.

In the gastrointestinal tract, fat-soluble vitamins are absorbed by the same mechanisms of lipid absorption. They form micelles with other lipid particles and enter into the intestinal epithelial tissues by passive diffusion. Absorption of these vitamins technically depends on the proper absorption of fat. Several studies showed that the inclusion of dietary fats in ration increases the absorption of fat-soluble vitamins. Fat-soluble vitamins are stored in the body, particularly in the liver and fatty tissues for future use.

Water-soluble vitamins are absorbed in the small intestine from dietary supplementation, and some of them can be synthesized by microbes in the large intestine. As these vitamins can not be stored in the body except vit-B12, a constant supply is mandatory for health regulation and performance.

In the case of excess intake of fat-soluble vitamins, hypervitaminosis may occur as they remain stored in the body.

Vitamins are micronutrients required in small amounts by birds to perform regular physiological functions and maintenance of health. Vitamin deficiency in diet and improper absorption may lead to metabolic disorders. Therefore, it is very important to ensure the proper amount of vitamins are absorbed and utilized.

There are many factors that may affect vitamin requirement and utilization in poultry. It may vary according to different breed and strains, birds age, health conditions and production status, environmental conditions and some other factors.

The presence of vitamin antagonists in diet may affect the activity of vitamins and make them inactive. Rancid fats are responsible for destroying fat-soluble vitamins. Sulfa drugs are known as vitamin K antagonist.

Vitamins are essential nutrients for the proper growth and production performance of birds. Deficiency of these nutritional compounds may cause metabolic disorders and leads to various nutritional diseases that are responsible for underperformance, death thus economical loss.

Vitamin A is known as retinol, which also occurs in the form of retinal and retinoic acid. It plays an important role in several physiological functions such as resisting infection and is technically known as the anti-infective vitamin.

In poultry, deficiency of vitamin A leads to high mortality. Impaired reproductive performances are observed in both male and female breeding birds. In mature birds, a significant reduction in egg production, fertility and hatchability may occur. In growing chicks, it may cause severe nervous system disorders and epithelial infection. Vitamin A deficiency adversely affects epithelial enterocytes thus causing a reduction in mucus-secreting goblet cells number.

Deficient chicks are susceptible to lachrymation conjunctivitis which leads to blindness. In breeders, interruption to the proper development of blood system in embryo may take place, therefore embryonic malfunction may occur.

Alternate names are ergocalciferol(D2) and cholecalciferol(D3). Among these two, Vitamin D2 is less effective than D3 for poultry. Vitamin D3 is known as the third major hormone that regulates calcium metabolism. Deficiency is rare in birds that are reared extensively and exposed to sunlight.

Vitamin D deficiency may result in only 15 percent and 50 percent absorption of available calcium and phosphorus respectively from the diet. Deficiency of Vitamin D reduces growth rate and feed intake in fast growing chicks. Beak and bones become soft, legs become weak that resulting in rickets in young birds and osteomalacia in adult ones. Thin and soft shelled eggs are often observed in the laying hens due to the deficiency for two to three months. In case of breeders, the newly hatched chicks can be stunted with soft bones because of the inappropriate calcification of eggshells.

Also known as alpha-tocopherol which is much more active than the other forms of tocopherol. It is a natural antioxidant that protects the birds against oxidative damage by scavenging free radicals hence increasing immunity. Vitamin E protects the sperm membrane from any damage and infection and therefore increases the sperm’s function in the male bird. It also supports vitamin A absorption and proper utilization.

Deficiency of vitamin E causes nutritional encephalomalacia or crazy chick disease, a condition in which the chick is unable to stand or walk. Deficient birds are prone to muscle degeneration and liver damage. In progeny production, an increase in early embryonic mortality and abnormal vascular system is observed frequently. Deficiency may decrease fertility in breeders.

Vitamin K stands for the Danish word Koagulation. There are three forms of vitamin K, they are Phylloquinone (K₁), Menaquinone (K₂), and Menadione (K₃). Vitamin K is essential for the synthesis of prothrombin and other blood clotting factors. It regulates many physiological functions such as electron transport, and has effects against coccidiosis too.

Deficiency of this vitamin may cause bleeding to death even from a minor injury to the birds. Young chicks are often seen as more susceptible than older birds. Vitamin K deficiency causes anaemia and the bone marrow becomes hypoplastic. The presence of sulfa drugs in diet or drinking water may inhibit the metabolic activities of Vitamin K.