I have a KWPN gelding that is quite a hot horse, but he does lose weight when travelling & competing.

   

As he is quite a hot horse ideally all of his energy should be sourced through oils and fibres which will provide a source of slow release energy for stamina, keeping clear of starch from cereals.

Although you could top his diet up with additional oils  high oil manufactured feeds and supplements often contain additional nutrients, specifically antioxidants, that will help improve oil utilisation.  Look for feeds with a high fibre and high oil content and try to keep the combined level of starch and sugar (NSC) below 10%.

Solution Mash from Rowen Barbary is cereal free and has a combined NSC level of just 6.65% so is ideal for horses that are hot headed.  With a very high fibre content this helps encourage slow rates of digestion throughout the hindgut and combined with 15% oil this helps to provide an excellent source of slow release energy for improved stamina.  Containing quality protein sources to help support overall muscle tone Solution Mash will help ensure excellent overall condition and is fully balanced in essential nutrients including antioxidants, digestive enhancers and added herbs.