PARTNER FEATURE ▶▶▶
Choosing the right metabolite matters
Poultry nutrition is complex and requires a good understanding to ensure animals can reach their full potential. Vitamins are just one aspect of this, such as vitamin D which has an impact on homeostasis, proper skeletal development and high production quality, among other things. This makes vitamin D essential and providing it in the best way possible, crucial.
BY WOUTER VAN DER VEKEN, HUVEPHARMA W
hen evaluating options in terms of supple- menting the vitamin, there are many different commercial metabolites available. Care should be taken when making the final selec-
tion though: metabolites matter, but not all are created equal. To be able to choose the right vitamin D supplementation, understanding the vitamin’s metabolic pathway in the animal itself and how supplementation can link into this, is funda- mental. Vitamin D3 is usually taken as the starting point of the metabolic pathway and there are two ways an animal can source this particular metabolite: either from a precursor in the skin or from the diet. However, the precursor route re- quires direct sunlight to be converted into vitamin D3, while access to direct sunlight is usually limited for most produc- tion animals. At the same time, standard raw materials in the diet often do not contain sufficient amounts of vitamin D3 on their own. This makes supplementation vital, but vitamin D3 is not the only option for this. Returning to the metabolic pathway itself, there are two dis- tinct steps to arrive at the active form of vitamin D. First, vita- min D3 is transported to the liver where the first hydroxyla- tion process turns it into 25-hydroxyvitamin D3. A second hydroxylation in the kidneys then transforms 25-hydroxyvita- min D3 into the 1,25-dihydroxyvitamin D3 hormone, consid- ered to be the active form of vitamin D. It is important to un- derstand that vitamin D supplementation can link in at every step of the pathway, giving producers a certain degree of flexibility. Briefly, there are three possible metabolites that can be supplemented: vitamin D3, 25-hydroxyvitamin D3 and
26 ▶ POULTRY WORLD | No. 6, 2020
1,25-dihydroxyvitamin D3. It is not easy to choose between these: each option has its own benefits and drawbacks, while there are also practical and regulatory aspects to keep in mind.
Active form of vitamin D As a first option, vitamin D3 is often considered the easiest and most economic metabolite to fulfil vitamin D require- ments. However, vitamin D3 depends on proper liver function to reach the active form of vitamin D. This should not be un- derestimated as the liver faces plenty of challenges in mod- ern animal production: mycotoxins, age, diet type, fatty liver syndrome and heat stress are all common examples of pa- rameters influencing good liver function. The same applies to 1-α-hydroxyvitamin D3, a synthetic precursor to the active hormone that still requires hydroxylation in the liver. Proper liver function is not a concern for supplementation with 1,25-dihydroxyvitamin D3 itself, as the hormone is already the active form of vitamin D. Although it can have a benefit, this also means that the natural feedback mechanism of the
PHOTO: SHUTTERSTOCK
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