VALIDITY OF NRC METHOD FOR ESTIMATING METABOLIZABLE ENERGY VALUE OF LABORATORY DRY CANINE DIETS

An equation to estimate the metabolizable energy (ME) content of pract ical dry canine diets, [metabolizable energy (ME(NRC), kcal/g)=3.50 x crude protein+8.46 x acid ether extract+3.50 x nitrogen-free extract] has been recommended by the National Research Council (NRC), which ass umes fixed digestibility for each nutrient. This estimation method is much more convenient than that of nitrogen-corrected metabolizable ene rgy (MEn) following the equation MEn=digestible energy-1.25 x digestib le crude protein. This study aimed to assess the validity of ME(NRC) t hrough a comparison with MEn determined by using 11 diets with 4 matur e male Beagle dogs. The relation between ME(NRC) and MEn was expressed as a quadratic equation (ME(NRC)=0.83MEn(2)-5.43MEn + 12.36, r(2)=0.9 56, P<0.01), suggesting that MEn is overestimated when the NRC method was applied to lower energy diets. It was also suggested that the stri ct estimation of MEn by means of fixed digestibility coefficients was impossible, because of the relatively wide variation in digestibility among dry canine diets.