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Effects of protected sodium butyrate (PSB) in broiler diets with reduced metabolizable energy (ME) content on production performance, intestinal histomorphometry and nutrient metabolizability were evaluated in two experiments. In one experiment, 384 one-day-old male chicks with an average weight of 44 ± 0.2 g were distributed into four treatment groups in a completely randomized design with six replications of 16 birds. The treatments consisted of i) a basal diet without reduced ME or PSB (BD); ii) BD with a 100 kcal/kg reduction in ME, without PSB; iii) BD with a 100 kcal/kg reduction in ME + 105 g/t PSB; and iv) BD with a 100 kcal/kg reduction in ME + 225 g/t PSB. Performance and carcass yield were evaluated. In the second experiment, 280 one-day-old male chicks were also distributed into four treatment groups in a completely randomized design with seven replications of 10 birds to evaluate metabolizability coefficients and intestinal development. The birds that received diet 3 had the best feed conversion ratio (FCR), final weight (FW) and weight gain (WG). Inclusion of PSB (105 and 225 g/t) in reduced-ME diets increased the metabolizability of crude protein coefficient at 35 days old. Birds that received diet 3 also had greater jejunal villus height at 21 and 35 days old. It is recommended to feed 105 g/t of PSB with a 100 kcal/kg reduction in ME until broilers were 35 days old.

The addition of protease to broiler diets may complement the action of endogenous enzymes and improve protein digestibility. Here, the authors evaluated the effect of adding protease to broiler diets that contained animal-based meal on bird performance, digestibility, and biometry of digestive tract organs. Four treatments, which contained animal- or plant-based meals with or without supplementary protease were compared, namely basal vegetable feed (BVF), BVF + protease (BFP), basal vegetable feed + animal byproduct meal (BFA), and BFA + protease. In the first experiment, 320 one-day-old Cobb 500® chicks were allocated to eight replicates with 10 birds per replicate. The experimental period was seven days, and nutrient metabolizability was evaluated. In the second experiment, 720 one-day-old Cobb 500® chicks were assigned to treatments in a similar manner, with six replicates and 30 birds per replicate, but the experimental period was 42 days. Significant differences (P