METHODS: A total of 256 Ross 308 one-day-old broilers (42.28±0.16 g) were randomly allocated in a 2×2 factorial arrangement to 32 pens with eight chicks per cage. Birds were fed one of four dietary treatments as follows: i) positive control (PCN; energy sufficient diet); ii) negative control (NCN; energy-deficient diet, -100 ME kcal/kg); iii) PCL (PCN plus 0.05% emulsifier); and iv) NCL (NCN plus 0.05% emulsifier). Growth performance was evaluated weekly whereas assessments for the carcass traits, digestibility, some blood metabolites, ileal morphology, and meat quality were measured on d 21 and d 35.

RESULTS: Birds fed the NCL diet had higher (p<0.05) body weights, daily gains, daily feed intake, and improved feed efficiency over the entire 35-day period. Improvements (p<0.05) for the ileal digestibility of crude fat, energy, and dry matter commensurate with longer (p<0.05) villus heights were also observed with emulsifiers in the NCL and PCL diets. For the carcass measurements, only the liver weights were increased (p<0.05) with emulsifiers in the supplemented groups. For blood metabolites, higher (p<0.05) lipase levels were noticed with emulsifiers in the NCL and PCL diets. In addition, marginal reductions (p = 0.076; p = 0.095, respectively) were also noted with emulsifiers for the total cholesterol and triglyceride contents on d 35. Regarding meat quality, breast muscle yellowness was increased (p<0.05) with emulsifier use in supplemented groups.