A Lactoferrin-Based Formulation Ameliorates Immune Dysfunction and Improves Growth in a Rat Model of Marginal Zinc Deficiency

Marginal zinc deficiency (MZD) affects immunity, growth, and development in children. Therefore, effective interventions using food-derived functional components to enhance immunity are required. Although the immunomodulatory effects of bioactives, such as LF, colostrum, and yeast β-glycan have been previously established, their combined effects on MZD is unknown. Therefore, the systemic regulatory effects of a lactoferrin-based MZD formulation were investigated in this study. To establish a MZD model, weaned Sprague–Dawley rats were fed a diet containing 10 mg/kg zinc for 5 weeks. The rats were administered a lactoferrin-based formulation via oral gavage. Compared with the control group, zinc deficiency significantly affected body weight gain, femur development, organ index, NK cell activity, splenic lymphocyte proliferation, and cytokine levels. These indicators significantly improved after the lactoferrin-based formulation intervention. The high-concentration lactoferrin formulation (LFC_high) group showed the most significant recovery compared with that of the other groups. The NK cell activity increased from 12.25% in the Model group to 34.50% in the LFC_high group, and splenic lymphocyte proliferation increased from 9.30% in the Model group to 17.31% in the LFC_high group. Furthermore, the lactoferrin-based formulation effectively regulated the gut microbiota, increasing the abundance of beneficial bacteria and decreasing the relative abundance of harmful bacteria. These preclinical findings provide a foundation for exploring interventions to address MZD and future research on targeted nutritional strategies.