Physiological and Molecular Effects of Zn–Fe Biofortified Alfalfa in Guinea Pigs Under Oxidative Stress

Oxidative stress is a major constraint limiting animal health and productive performance by disrupting redox homeostasis, mitochondrial function, intestinal integrity, and mineral metabolism. Agronomic biofortification of forage with essential trace minerals represents a promising nutritional strategy; however, its physiological and molecular mechanisms remain poorly understood. This study evaluated the effects of dietary zinc–iron (Zn–Fe) biofortified alfalfa on oxidative stress, antioxidant defense, mineral transport, mitochondrial bioenergetics, intestinal barrier integrity, inflammatory responses, tissue mineral deposition, and growth performance in guinea pigs. Forty-eight male guinea pigs were allocated to six experimental groups according to dietary treatment (control, Zn-biofortified alfalfa, or Zn–Fe biofortified alfalfa) and oxidative stress status. Oxidative biomarkers, antioxidant enzyme activities, inflammatory mediators, mineral concentrations, targeted RT–qPCR, mitochondrial function, intestinal histomorphology, and multivariate physiological analyses were performed. Zn–Fe biofortified alfalfa markedly reduced reactive oxygen species, malondialdehyde, protein carbonyls, 8-hydroxy-2′-deoxyguanosine, advanced oxidation protein products, and the oxidative stress index while significantly increasing superoxide dismutase, catalase, glutathione peroxidase, total antioxidant capacity, and the glutathione redox ratio. Targeted gene-expression analysis demonstrated coordinated upregulation of intestinal mineral transporters (ZIP4, DMT1, and MT1), activation of the Nrf2 antioxidant pathway, increased expression of mitochondrial regulatory genes, and suppression of inflammatory mediators. These molecular responses were accompanied by improved ATP production, mitochondrial membrane potential, respiratory-chain activity, preservation of intestinal villus architecture, enhanced expression of tight-junction proteins, increased tissue Zn and Fe deposition, superior feed efficiency, and greater body weight gain. Integrated physiological analyses consistently identified the Zn–Fe biofortified treatment as the highest-performing physiological phenotype, indicating coordinated adaptation across multiple biological systems. These findings demonstrate that Zn–Fe biofortified alfalfa enhances oxidative stress resilience through simultaneous regulation of mineral transport, antioxidant defense, mitochondrial bioenergetics, intestinal barrier integrity, and systemic physiological performance. Agronomic biofortification of forage therefore represents a promising nutritional strategy for improving animal health, mineral utilization, and productive efficiency under oxidative stress.