The impact of dietary fiber and fat levels on total tract digestibility of energy and nutrients in growing pigs and its consequence for diet formulation

The effect of dietary fiber and fat content on energy and nutrient digestibility was evaluated and regression equations were developed to predict dietary digestible energy (DE) content. A total of 125 barrows (39 kg BW) were fed with diets based on five wheat bran (0, 150, 300, 450, and 600 g/kg) and five added fat levels (0, 25, 50, 75, and 100 g/kg) in a 5×5 factorial arrangement. DE intake was adjusted as 2.6 times of the maintenance requirements. Results show that despite the fact that both fiber and fat digestibility are significantly influenced by fiber×fat interaction, digestibility of energy is principally affected by dietary fiber content. The model calculation indicates that DE content of the feed can be more precisely compute, if digestibility of energy is used in diet formulation rather than addition of energy contents of calculated digestible nutrients, so far as the digestibility coefficients of energy and nutrients are derived from regression equations.