Estimation of metabolizable energy equivalency of Bacillus Subtilis spore for male broiler chickens

There are many studies on the effects of probiotics on performance of broiler chickens, but none of them has evaluated the metabolizable energy (ME) equivalency values of probiotics. The aim of this study was to determine the metabolizable energy equivalency value of Bacillus subtilis spore and its potential for decreasing feed ME content and cost. One hundred seventy-six day-old male broilers (Ross 308) were used in a completely randomized design, with 11 treatments, of four replicates each, and 4 chickens per cage as an experimental unit. Dietary treatments contain a basal diet (2800 kcal/kg) containing graded levels of ME (2850, 2900, 2950, 3000 and 3050 kcal/kg) and Bacillus subtilis (4 × 109 CFU/g DSM 17299) at 0.05, 0.10, 0.15, 0.20 and 0.25 g/kg. Graded levels of feed ME and added Bacillus subtilis were used as independent variables to derive regression equation of performance traits on independent variables. The derived regression equations of body weight and feed conversion ratio (FCR) for ME were set to be equal with those obtained for Bacillus subtilis and were solved; Bacillus subtilis equivalence value for ME was calculated by subtracting the obtained value from ME content of the basal diet. In comparison to the basal diet, added Bacillus subtilis significantly improved the body weight and feed conversion ratio. Metabolizable energy equivalency of Bacillus subtilis for FCR and body weight at 42 days of age was 360366 and 485823 kcal/kg, respectively. Results showed that ME value of Bacillus subtilis was decreased by advancing chickens ag­e.