Effects of dietary L-Ornithine L-Aspartate supplementation on growth performance, immune function, and intestinal health in lipopolysaccharide-challenged broilers.

This study evaluated the effects of dietary L-Ornithine L-Aspartate (OA) supplementation on growth performance, immune response, intestinal health, and cecal microbiota in broilers challenged with lipopolysaccharide (LPS). A total of 624 one-day-old Arbor Acres broilers were assigned to a 4 × 2 factorial arrangement with four dietary OA levels (0, 400, 600, and 800 mg/kg) and two challenge treatments (saline or LPS). Birds were intraperitoneally injected with LPS (1 mg/kg BW) or sterile saline on d 23, 25, and 27, and the experiment lasted 42 d. LPS challenge impaired growth performance, induced systemic inflammation, reduced microbial diversity, and disrupted intestinal homeostasis in broilers. Dietary OA supplementation improved growth performance, attenuated inflammatory responses as evidenced by reduced serum proinflammatory cytokine levels, with significant OA × LPS interactions observed for tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), and by suppressing splenic expression of inflammatory cytokines, toll-like receptor 4 (TLR4), and myeloid differentiation factor 88 (MyD88). Moreover, OA supplementation improved intestinal barrier function as shown by reduced serum diamine oxidase activity, enhanced jejunal morphology, increased secretory immunoglobulin A (sIgA) expression, and the abundance of beneficial bacterial taxa in the cecum. In conclusion, dietary OA supplementation could improve growth performance in broilers by alleviating inflammation, improving immune homeostasis and intestinal health, which may be associated with modulation of the splenic TLR4/MyD88 signaling pathway. Based on a comprehensive evaluation of growth performance, immune regulation, intestinal health, and inflammatory responses, 400 mg/kg was identified as the optimal dietary inclusion level under the conditions of the present study.