CONCEPTS, SCIENTIFIC BASES, STRUCTURE AND VALIDATION OF THE FRENCH HORSE NET ENERGY SYSTEM (UFC)

The French horse net energy (NE) system is based on energy utilization for maintenance and work, as maintenance accounts for 50-90% of total energy requirements of horses. The NE value of feeds was computed fro m their digestible energy (DE) content as determined in horses, the ra tio between metabolizable energy (ME) and DE as measured in horses and the efficiency of ME utilisation for maintenance (km). The latter was based on three factors: firstly, the energy cost of eating as measure d in horses and ponies, secondly, the assumed proportions of absorbed energy supplied by the various nutrients and thirdly, the ATP producti on potentials of nutrients and the efficiencies of energy utilization for maintenance from glucose, lactate, amino acids and long chain fatt y acids (as measured in monogastrics) and volatile fatty acids (VFA) ( as measured in ruminants), The NE value of feeds was related to that o f barley and expressed in Horse Feed Unit (UFC). The validity of the h ypotheses used in the UFC system was tested by indirect calorimetry in light horses and ponies fed near the maintenance level. The km of pur e feeds and nutrients fed to ponies agreed with the values obtained in monogastric or ruminant animals and used to set up the system, Furthe rmore, a total of 26 horses of light breeds was fed 12 diets expected to give large variations in the proportions of digestion end-products. The differences between the measured and the predicted km values for forages and mixed diets averaged - 0.6 +/- 1.2%. These results support the hypotheses used in this NE system and demonstrate its higher accu racy as compared to a DE system. Feeding tables were elaborated (INRA, 1990) and sets of equations were computed to predict the NE value of simple feeds (forages, concentrates) and compound feeds from their che mical composition. (C) 1997 Elsevier Science B.V.