Whey protein is the highest quality protein you can get, with an amino acid profile that almost perfectly matches the profile of amino acids that muscles need to build and grow. Whey protein is also high in branched chain amino acids which provide muscles with a valuable source of energy. Not surprisingly, whey protein is sought after by horse owners and trainers to add to diets where horses need to 'muscle up' and particularly in cases where additional topline is needed.

However, there is a bit of a catch that many people fall into when purchasing this ingredient. You can buy 'whey powder' which is relatively cheap and sounds like what you should be buying to provide your horse with whey protein. The catch is, whey powder is 'whole whey' which only contains around 13% whey protein and is over 50% lactose. Using 'whey powder' provides horses with very little whey protein (there is only 13 grams of protein in every 100 grams of whey powder) and puts a lot of lactose into their gut. Adult horses don't have the lactase enzyme necessary to digest lactose (essentially they are lactose intolerant) so feeding 'whey powder' can lead to diarrhea and colic if too much is fed.

If you want to add whey protein to your horse's diet, look for whey protein concentrate or whey protein isolate. These products have had most of the lactose removed (they will contain less than 10% lactose) and will be 75% to 90% whey protein. The whey protein isolate is generally produced for use in human food products and is often quite a bit more expensive than whey protein concentrate, so if you want to use whey protein, the best choice for your horse's ration is a whey protein concentrate.

There has been a bit of discussion in the last couple of years about whether vitamin K should be added to horse feeds and if so, which form is the most effective in supporting bone development.

Vitamin K plays a complex role in the body. It is best known for its role in blood clotting, but it is also involved in many other functions including bone development.

There are many different forms of vitamin K including K1 (phylloquinone), K2 (menaquinone) and K3 (menadione). K1 comes predominantly from green plants, K2 is produced by bacteria and K3 is the synthetic form of vitamin K. These 3 primary forms of vitamin K are then converted in the body to several vitamin K homologs, with each homolog having a different role in the body. The homolog 'menaquinone-4' is the one that is recognised as being most important in bone formation.

It has been suggested that the synthetic form of Vitamin K (K3 or menadione) is unable to play an effective role in bone formation. However, a recent study published by Terachi et al (2011) in the Journal of Animal Science showed that horses supplemented with K3/menadione had the highest plasma menaquinone-4 concentrations compared to horses supplemented with phylloquinone or menadione-4.

The authors concluded that 'menadione is likely the best source of vitamin K for bone health in horses'.