NUTRITION ▶▶▶
Botanical vitamin D tailored for high performance
BY MURAT DEVLIKAMOV, PHYTOBIOTICS V
itamin D is an essential micronutrient required by all animals for the function and maintenance of calcium (Ca) and phosphorus (P) metabolism. Ani- mals can produce vitamin D through skin expo-
sure to UV light. However, for livestock this is possible only to a limited extent under commercial production conditions, such as barn and cage farming. For this reason, supplemen- tation of vitamin D via feed becomes increasingly important to prevent adverse deficits. In addition, the requirements of modern and commercially-raised poultry are increasing due to high production levels and variable needs at different stages of production.
Metabolic pathway In most cases, vitamin D supplemented through feed is not directly available to the animal and must first be metabolized by endogenous enzymes. The inactive vitamin D, also known as cholecalciferol, is first hydroxylated to calcidiol in the liver. Calcidiol is the form of vitamin D that circulates in the blood and is defined as the ‘storage form’. Subsequently, conversion to the bio-active form of vitamin D, calcitriol, takes place mostly in the kidneys. As calcitriol is the most active metabo- lite, it is essential to mediate calcium and phosphorus uptake from the gastro-intestinal tract, for the mineralization of bones and eggshell formation. Problems can occur when external or physiological factors in- hibit the conversion steps towards active vitamin D (Figure 1). For example, in the starter phase broilers do not have a com- plete enzymatic system that supports hydroxylation in the liv- er, so the growing organism could face a vitamin D deficit. Whereas in laying hens the production of bio-active vitamin D decreases with age due to metabolic deficiencies of the liver and kidneys. Consequently, both laying performance and egg- shell quality decline towards the end of the production. The finding that higher cholecalciferol supplementation does not necessarily bring an improvement, while the use of the con- verted vitamin D metabolites does, highlights the importance
Vitamin D supplemented through feed is not directly available to the animal and must first be metabolized by endogenous enzymes. The next step in animal nutrition is supplementing vitamin D based on physiological needs, using phytogenic sources. Bio- active vitamin D may be the solution as phytogenic sources have the benefit of being directly available.
of correct supplementation. Useful management tools to sup- port the animal’s vitamin D metabolism may be to adjust the calcium source, e.g. administration of additional coarse parti- cle limestone (e.g. oyster shells), along with constant attention to the Ca:P ratio of the diet, especially in the late production stages. Finally, certain phytogenic sources provide an excellent instrument for targeted vitamin D supplementation at crucial
Figure 1 - External and physiological factors which can influence the vitamin D metabolism.
Production Disorders
1α-Hydroxylase
Endogenous Enzyme
Production Calcitriol 25-Hydroxylase Cholecalciferol Liver
Mycotoxins in Feed
Calcidiol
Kidneys 2
Production Diseases
Heat Stress
Stress/ Inflammation
▶ POULTRY WORLD | No. 4, 2021
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