Starch is a really good energy source.
However quantities delivered at each meal must be very well controlled.
In case of overdose (more than 400 g of crude starch/100 Kg of LW/meal according to Potter, 1992), it becomes difficult for the horse to digest and starch passes through the large intestine which leads to its fermentation by lactic bacteria. This leads to troubles of the microbial ecosystem in the large intestine (pH decrease, lactic and acetic contents increase, decrease of the cellulolytic activity), which can lead to colic and laminitis.
Starch quality also plays a main role.
When starch is cooked (case of pelleted feed), its digestibility increases, which allows to raise the ingestion threshold. Then better valorised by the animal, starch submitted to a thermic treatment allows to limit ”waste” (Rosenfeld and Autsbo 2009).
Plant origin also greatly influences ante-caecal digestibility of starch: that is why raw materials are strictly selected to be incorporated in Royal Horse feeds.
Note for instance that wheat bran which is an outstanding raw material rich in hemicellulose, as well as in starch can perfectly be registered in the list of horse feeds even at important % if we want to provide hemicellulose in sufficient quantity in feeds.
The most important being to keep around 25 % of starch (that to say 2 to 2.5 less than cereal starch contents, (oat, barley, corn) in final feed formula.
For sustained efforts, in addition to starch (carbohydrates), plant fats (lipids) will be provided.
(Research and Development Department InVivo NSA, Royal Horse 2010).