parathyroid glands in terms of the amount of 1,25- dihydrox- yvitamin D3 is by-passed. This mechanism is regulated via the production of parathyroid hormone (PTH) in relation to the presence of 1,25-dihydroxyvitamin D3, and plays a pivotal role in the animal’s vitamin D homeostasis. Under normal cir- cumstances, the levels of active 1,25-dihydroxyvitamin D3 are regulated quite well to prevent overproduction of the active 1,25-dihydroxyvitamin D3 and the associated toxicity risk. From a practical point of view it is important to remember 1,25-dihydroxyvitamin D3 itself has a very short half-life. This makes it a difficult parameter to assess the animal’s overall vitamin D status, especially in relation to dietary vitamin D supplementation. As a third option, 25-hydroxyvitamin D3 combines the bene- fits of the other two without the risks. It joins the vitamin D metabolic pathway after hydroxylation in the liver takes place, hence it does not rely on the organ to achieve effective vitamin D supplementation, although still one step removed from the main active form of vitamin D – this minimises the potential risks. Evaluating the metabolite’s supplementation
is also fairly straightforward because serum 25-hydroxyvita- min D3 can be easily detected and responds rapidly to changes in supplementation.
25-hydroxyvitamin D3 Keeping the above in mind, it is clear that the underlying physiology of vitamin D supplementation should be consid- ered when evaluating which metabolite to add to the ani- mals’ diet. Selecting 25-hydroxyvitamin D3 as the preferred option thus makes sense. When looking at the current com- mercial market, it is important to realize that not all 25-hy- droxyvitamin D3’s are the same: depending on the nature of the production process, there are distinct differences in terms of bioavailability and stability. Bio D, a novel 25-hy- droxyvitamin D3 product, has been designed with precisely this in mind. It is produced via fermentation, resulting in great 25-hydroxyvitamin D3 bioavailability and stability. As such, Bio D helps producers to meet their animals’ vitamin D requirements, effectively supporting them from start to finish.
▶ POULTRY WORLD | No. 6, 2020
Vitamin D3 is usually taken as the starting point of the metabolic path- way and there are two ways an animal can source this par- ticular metabo- lite: either from a precursor in the skin, or from the diet.
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