Evaluation of soybean meal bioactive peptides and Spirulina powder as antibiotic alternatives on growth performance,...

This study aimed to evaluate the effects of dietary soybean-derived bioactive peptides (SBP) and Spirulina powder (SP) as antibiotic alternatives on performance, amino acid digestibility, antioxidant status, and intestinal health-related gene expression in broiler chickens. A total of 250 male and female Ross 308 one-day-old chicks were used in a completely randomized design with 5 treatments, 5 replicates, and 10 chicks per replicate. The experimental treatments included: (1) a control diet consisting of the standard basal diet without any additive (CON); (2) a basal diet supplemented with avilamycin at 100 g/ton of feed (ANT); (3) a basal diet supplemented with SBP at 2 g/kg of feed (SBP); (4) a basal diet supplemented with SP at 2 g/kg of feed (SP); and (5) a basal diet supplemented with a combination of 1 g/kg SBP and 1 g/kg SP (SBP-SP). Body weight gain and feed intake during the starter and grower phases, as well as over the entire experimental period (1-42 d), was significantly greater in birds fed the SBP-SP diet compared with the CON and SP groups (P < 0.05). Broilers fed the SBP-SP, ANT, and SBP diets exhibited higher apparent ileal digestibility of Methionine, Isoleucine, Threonine, Aspartic acid and Glutamic acid compared with those fed the CON and SP diets (P < 0.05). Dietary inclusion of SBP-SP and ANT led to a substantial increase in both villus height, villus surface area, and the villus height to crypt depth ratio when compared to the CON group. Dietary supplementation with SP and SBP-SP significantly boosted the IBV antibody titers at both 21 d (P = 0.006) and 42 d (P = 0.017) compared to the CON, ANT, and SBP groups. The relative weight of the Bursa of Fabricius and Thymus was markedly increased in birds supplemented with SBP-SP and SP compared to those in the CON and SBP groups (P = 0.015). Broilers receiving the SBP-SP and SP treatments exhibited significantly higher levels of TAC, SOD, GPx, and CAT compared with the CON and ANT groups. The mRNA levels of IL-1β and TNF-α were markedly downregulated in birds receiving the SBP-SP diet compared to all other experimental groups (P < 0.05). The expression of ZO-1, MUC2, SLC15A1, SLC6A19 and SLC7A1 was significantly upregulated in the SBP-SP group compared to the CON group (P < 0.05). Collectively, these findings indicate that the combined use of SBP and SP exerts synergistic effects on digestive efficiency, intestinal function, and physiological status, suggesting that this combination may serve as a promising natural alternative to antibiotic growth promoters in broiler nutrition.