Importance of Vitamin D in ensuring good bird health

An adequate supply of vitamins and minerals is necessary in poultry for boosting defences and allowing the bird to reach its full genetic potential.

Vitamin D, for example, plays a vital role in the regulation of calcium and phosphorus metabolism, which are key to optimising the skeletal system by strengthening bones, beaks and claws.

The two primary concerns relating to skeletal disorders in poultry are: osteoporosis in egg-laying hens and leg problems caused by rapid bone growth and increased daily gains in broilers.

While calcium and phosphorus play a critical role, the importance of Vitamin D in this process must not be overlooked.

Vitamin D, which is derived either from the diet or from sunlight via the skin, is biologically inactive and so requires “activation” through enzymes.

In practice, vitamin D3 is absorbed from the bird’s intestine and is transported to the liver, where it is converted into a metabolite (25(OH)D3), and then on to the kidney, where it becomes an active hormonal compound called calcitriol (1,25(OH)2D3). Calcitriol is key to controlling calcium levels in the body.

This chemical process is regulated by two specific hormones – namely the parathyroid hormone and calcitonin, in response to blood calcium levels.

Above: The Vitamin D Pathway

If blood calcium is low, parathyroid hormone is induced, which leads to an increase in calcium absorption in the intestine, mobilization of calcium from the bones and a reduction in calcium excretion via the kidney.

If blood calcium is high, the thyroid gland secretes calcitonin, which results in a reduction in calcium absorption in the intestine, lower calcium release from the bones, and increased calcium excretion.

Similar chemical processes involving the activation of vitamin D control levels of phosphorous in the chicken.
 

Vitamin D has other bone-related functions, in addition to mineral mobilisation from the bone to correct deficiencies.

In the intestine, it promotes the creation of calcium-binding proteins, and stimulates calcium, phosphorus and magnesium absorption.

A vitamin D deficiency can challenge the process of bone formation as it reduces mineral deposition on the protein matrix. This can lead to the development of rickets in young birds and osteomalacia in adult birds.

In layers, cage fatigue is another common problem in birds with high egg production rates, caused by inadequate calcium levels to meet egg production demand. The bird preferentially removes calcium stored in her bones to meet the demand for eggs, giving rise to bones which become soft and fracture easily over time.

Supplementation with calcium and vitamin D3 can reduce and relieve such disorders.
 

The functions of vitamin D stretch beyond bone integrity, as it affects a range of other organs and tissues, including the pancreas, parathyroid glands, bone marrow, and certain cells of the ovary, brain and stomach.

Vitamin D is extremely important for chick development and growth. Firstly, it is required for embryonic development, where it stimulates yolk calcium mobilization for the chick.

Vitamin D is also involved in calcitriol production which is required for the transport of eggshell calcium across the chorioallantoic membrane to the embryo.

In addition, calcitriol is involved in the development of the immune systems of chicks, which can be suppressed by a vitamin D deficiency.

This means that all poultry feedstuffs need to be supplemented, and the form of vitamin D included is crucial.

The D3 form of the vitamin has a high bioavailability, while the D2 form has a low bioavailability. But it is the metabolites of vitamin D3 that are the most effective sources.

These vitamin D3 metabolites can be added “over the top” to diets already supplemented with the inactive form of vitamin D3.

Additional supplementation of such metabolites can improve leg disorders and enhance the utilization of phytate-phosphorus and trace minerals. An improved broiler body weight can be demonstrated, along with a reduced incidence and severity of bone disorders.

Such metabolites are available commercially in a variety of forms.

Panbonis is a product, processed from the plant Solanum glaucophyllum, that contains the active form of vitamin D3 in a glycosidic bound form (1,25(OH)2D3-glycoside). This product is immediately active in the intestine following uptake, as it does not have to undergo the two activation stages within the body, which makes it rapidly available and effective for the prevention of bone anomalies. It is supplemented on top of the formulated diet.

Other benefits of Panbonis include the improvement in weight gain and feed conversion, reduced phosphate output due to increased phosphorus utilisation, improved shell quality, reduction in broken eggs, improved hatchability and fewer processing rejects and downgrades in the factory.

Panbonis is certified for use on both conventional and organic systems.