vitamin k ISSUE 32.qxd:Jerkins feature.qxd
26/11/10
14:34
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NUTRITION
Fresh pasture contributes to vitamin K intake
Vitamin K – the forgotten vitamin Vitamin K, which is classified as a fat soluble vitamin, has been present in racing rations for many years, both in forages and as one of a range of vitamins and minerals added to concentrate feed. To date, vitamin K has not been a fashionable vitamin, unlike vitamin C or vitamin E, which have received a lot of attention from a research perspective. Vitamin K is probably best known for its function in blood clotting, but more recently its role in bone metabolism has been highlighted in humans and horses. Here we will explain the role of dietary vitamin K in the context of racing and touch on some new research that has emerged in horses with respect to bone metabolism. By Catherine Dunnett Bsc, Phd 34 TRAINERMAGAZINE.com ISSUE 32
Many forms of vitamin K Vitamin K is in fact not a single vitamin but a group of vitamins with a similar structure and resulting action. Two forms of vitamin K that you may be familiar with are phylloquinone (or vitamin K1) and menaquinone (or vitamin K2). Vitamin K1 is found in green leafy plants including grass both fresh and dried. Vitamin K2 is synthesised by bacteria present in the digestive tract, particularly in the hindgut. There are also various synthetic forms of vitamin K that are available for use in horse feed. Each of these forms of vitamin K have a similar core structure but with different side chain configurations, which can affect the absorption of vitamin K from the digestive tract. Interestingly, menadione – which is the synthetic form of vitamin K often used in vitamin and mineral premixes and supplements – has no side chain. This