Effects of dietary protease and protease-probiotic combination on growth performance, nutrient digestibility, and intestinal immune response in broiler chickens.

A study was conducted to evaluate the effects of dietary supplementation with a microbial protease alone or in combination with probiotic components on growth performance, nutrient utilization, amino acid digestibility, and intestinal immune response in broiler chickens. A total of 240 one-day-old male Cobb 500 broilers were randomly assigned to 3 dietary treatments with 8 replicate pens of 10 birds each: a control diet, control supplemented with 0.1% Pearlzyme 1 (microbial protease), and control supplemented with 0.1% Pearlzyme 2 (microbial protease combined with probiotic components). Birds were reared for 21 d and fed a starter diet from d 0 to 12 and a grower diet from d 13 to 21. Growth performance was measured throughout the experiment, and energy utilization, nitrogen utilization, and apparent ileal digestibility of amino acids were determined during the grower phase. To evaluate intestinal immune response, 1 bird per pen was challenged with lipopolysaccharide on d 19, and intestinal morphology and ileal gene expression were assessed 4 h later. Both supplements increased apparent metabolizable energy (P = 0.003), nitrogen-corrected apparent metabolizable energy (P = 0.003), gross energy digestibility (P = 0.014), and dry matter digestibility (P = 0.002) compared with the control diet. Pearlzyme 2 increased feed intake (P = 0.018), body weight gain (P = 0.028), and nitrogen retention (P = 0.030) during the grower phase. Pearlzyme 1 improved apparent ileal digestibility of several amino acids, including threonine (P = 0.047), phenylalanine (P = 0.035), tyrosine (P = 0.034), and cysteine (P = 0.018). Intestinal morphology and tight junction gene expression were not affected by dietary treatment (P > 0.05). However, Pearlzyme 2 reduced ileal expression of interleukin-1 beta (P < 0.001) and interleukin-10 (P = 0.005) following lipopolysaccharide challenge. These findings suggest that microbial protease supplementation can improve nutrient utilization in broiler diets, and combining protease with probiotic components may provide additional benefits for growth and intestinal immune balance in antibiotic-reduced poultry production systems.