Effects of dietary octapeptin supplementation on growth performance, intestinal morphology, immune function, and serum metabolism of weaned piglets

Abstract Weaning stress severely impairs the health and growth of piglets. Octapeptin is a type of polypeptide with immunoregulatory activity. Therefore, the present study was conducted to investigate the effects of a novel octapeptin on growth performance, intestinal morphology, immune function, and serum metabolism in weaned piglets. A total of 240 21-d-old piglets with BW of 7.06 ± 0.28 kg were randomly assigned to five dietary treatments according to their initial BW and sex and fed a basal diet (CON) or a basal diet supplemented with octapeptin at 10, 20, 40, or 80 mg/kg (O10, O20, O40 and O80) respectively. Subsequently, eight piglets were selected from the CON group and the O80 group (superior growth performance), respectively, and slaughtered for further mechanistic investigation after 28-day feeding trial. Dietary octapeptin supplementation with 80 mg/kg significantly reduced the feed-to-gain (F/G) ratio during days 15–28 (P < 0.01). Moreover, as the octapeptin level increased, the F/G ratio decreased linearly across all growth phases, while body weight (BW) during days 0–28 and average daily gain (ADG) over the entire period increased linearly (P < 0.05). Dietary supplementation with 80 mg/kg octapeptin (O80) significantly increased villus height and villus height-to-crypt depth ratio (P < 0.05). Furthermore, the O80 group exhibited significantly reduced levels of cytokines interferon-gamma (INF-γ) and interleukin-6 (IL-6) in spleen (P < 0.05), increased mRNA expression of IL-10 in the ileal mucosa (P < 0.05), and decreased mRNA expression of IL-8 in mesenteric lymph nodes (P < 0.05). Serum metabolomics analysis demonstrated that dietary supplementation with 80 mg/kg octapeptin markedly altered the metabolic profile, enriching pathways associated with indole diterpene alkaloid biosynthesis, lysine biosynthesis and steroid biosynthesis. Our findings indicated that dietary supplementation with octapeptin could improve growth performance of weaned piglets, which was associated with linearly increased average daily gain and decreased feed-to-gain ratio. Notably, dietary supplementation with 80 mg/kg octapeptin exhibited the optimal effect on growth performance, and further mechanistic analysis revealed that this octapeptin supplementation at this level enhanced ileum development, improved intestinal immune function, and modulated serum metabolism.