Dietary nano-manganese supplementation enhances intestinal integrity, muscle traits, and tight junction protein expression in broilers.

Background and Aim: Manganese (Mn) is an essential trace mineral for poultry, supporting skeletal development, metabolism, and intestinal health. Conventional inorganic Mn sources often have low bioavailability, leading to oversupplementation, environmental excretion, and mineral imbalance. Mn nanoparticles (Mn-NP) offer improved absorption and reduced environmental burden, but their graded effects on broiler growth, intestinal morphology, meat quality, and tight junction proteins remain underexplored. This study evaluated the impact of dietary Mn-NP supplementation on productive performance, serum metabolites, jejunal architecture, and intestinal barrier function in broilers. Materials and Methods: A total of 240-day-old broiler chicks were randomly assigned to six groups (n = 40; 4 replicates of 10 birds) and fed a basal diet (control), bulk Mn (80 mg/kg), or Mn-NP at 20, 40, 60, or 80 mg/kg for 35 days. Growth performance, visceral organ development, serum biochemistry, meat physicochemical attributes, jejunal morphology, and messenger RNA expression of claudin-5 (CLDN-5) and zonula occludens-1 (ZO-1) were evaluated. Results: Mn-NP supplementation did not significantly alter body weight or feed intake. However, the 40-Mn-NP group showed improved feed conversion ratio during weeks 2 and 3 compared with the 80-Mn-NP group. The gizzard weight decreased significantly at 40-Mn-NP, while bulk Mn increased cecal weight. Serum metabolites, including liver and kidney markers, remained unaffected across treatments, indicating no toxicity. Muscle pH45min was higher in 20- and 40-Mn-NP groups, while pH24 was reduced in the 40-Mn-NP and bulk Mn groups. Birds supplemented with 80-Mn-NP exhibited larger muscle fibers, whereas the 20-Mn-NP group showed higher fiber density. Jejunal villi were longer and crypts deeper in the 20-Mn-NP group, while tight junction proteins (CLDN-5, ZO-1) were significantly upregulated in the 60-Mn-NP group. Conclusion: Mn-NP supplementation at 40-60 mg/kg optimally enhanced feed efficiency, jejunal morphology, and intestinal barrier integrity without adverse health effects. These findings highlight Mn-NP as a sustainable alternative to conventional Mn supplementation, improving gut health and meat quality while reducing mineral excretion. Future studies should validate long-term safety and commercial-scale applications.