Protein requirements and allowances of the exercising horse

Protein requirements are evaluated using either factorial method which results to different protein/energy -ratios for maintenance and work and with intensity of exercise (NRC, 2007) or a constant ratio, assuming that the ratio is the same for work and maintenance whatever the intensity (all other systems). The increments of the requirements with the intensity of exercise in respect of maintenance (base = 100) is close in all the European systems (125-200 percent) but much higher than that of NRC systems (110-140 percent) whatever the intensity. Extra requirements to support the increase of the muscle mass in the adult individuals are not well established. Additional requirements are requested to support simultaneous late growth and early training in young horses. Requirements in essential amino acids are not yet well defined except for lysine mainly in growing horses. The benefit of branched-chain amino acids supplementation is not yet demonstrated. The effect of excess of protein in diet is still questionable. Recommended allowances including requirements for different body weight and exercise intensity are provided by all the systems but the range of intake capacity diet composition and key body condition score along the training and competition periods are note always suggested.