Immunologically active peptides (IAP) are important bioactive peptides with potential antioxidant, anti-inflammatory, and immunomodulatory properties. However, their application in broiler production has not been systematically evaluated. This study investigated the effects of dietary IAP supplementation on growth performance, carcass traits, meat quality, selected serum biochemical indices, and ileum inflammatory cytokine expression in broilers. A total of 180 one-day-old Ross 308 male broilers were randomly assigned to 3 dietary treatments with 6 replicates per group for 42 d: a basal diet (CON), and the basal diet supplemented with 500 g/t or 1000 g/t IAP. Overall treatment tendencies were observed for final body weight (BW) and average daily gain (ADG) (p = 0.100; p = 0.096), with numerically higher values observed in broilers receiving 500 g/t IAP. Dietary supplementation with 500 g/t IAP significantly improved feed conversion ratio (p < 0.05). Across increasing dietary IAP levels, significant quadratic responses were observed for final BW, ADG, and FCR (p < 0.05), indicating nonlinear responses to increasing IAP supplementation levels. In addition, serum superoxide dismutase (SOD) activity was significantly increased in broilers receiving 500 g/t IAP compared with the control group (p < 0.05), and a significant quadratic response was observed across dietary IAP levels (p < 0.05). Furthermore, dietary IAP supplementation significantly reduced ileum interleukin-1β (IL-1β) mRNA expression in the 500 g/t group (p < 0.05), and IL-1β expression exhibited a significant quadratic response across IAP supplementation levels (p < 0.05). In conclusion, dietary supplementation with IAP, particularly at 500 g/t, improved feed efficiency, increased serum SOD activity, and reduced ileal IL-1β mRNA expression in broilers without compromising carcass characteristics or meat quality. These findings indicated that IAP has potential as a functional feed additive for further evaluation in broiler production.

Alpha-ketoglutarate (AKG) supplementation has been explored as a nutritional strategy to mitigate the negative effects of protein restriction. This study aims to evaluate the effects of supplementing a low-protein diet with AKG on growth performance, diarrhea incidence, and fecal nutrient digestibility in weaned piglets. A total of 60 weaned piglets (initial body weight: 7.53 kg; age: 28 days old) were randomly distributed into three dietary treatments with five replicates per group, for a 42-day experimental period. The treatments consisted of a control diet (CT), a low-protein diet (LP), and a low-protein diet supplemented with 1000 g/t AKG (AKG). Fecal samples were collected on days 40–42 to determine the apparent digestibility of nutrients. The results showed that the feed conversion rate (FCR) in LP-group piglets were significantly higher than that of the CT group (p = 0.028), while the crude protein (CP) digestibility was significantly lower in the LP group compared with the CT group (p = 0.038). However, supplementing the low-protein diet with 1000 g/t AKG effectively mitigated these negative effects. Pigs in the AKG group had reduced incidence of diarrhea between days 1 and 14 compared to CT group (p = 0.041). These findings suggest that incorporating 1000 g/t AKG into low-protein diets may reduce post-weaning diarrhea and improve growth performance of piglets.