Zinc and animal health: an in-depth exploration of its role in physiological functions and regulatory molecular mechanisms.

Zinc, an essential trace element, plays a pivotal role in maintaining animal health and physiological functions. This review comprehensively examines zinc metabolism-including absorption dynamics across species (poultry, ruminants, and non-ruminants), transport mechanisms, storage in tissues, e.g., the liver, and excretion pathways-and its multifaceted effects on animal health. Zinc critically regulates aspects of growth and development, particularly bone formation, as its deficiency induces skeletal deformities in young animals. It modulates immune function through zinc finger proteins, influencing immune organ integrity, lymphocyte proliferation, and cytokine expression. Reproductive performance is significantly affected by zinc, with its deficiency causing impaired spermatogenesis; delayed sexual maturity in males; and reduced litter size, embryonic survival, and placental function in females. At the molecular level, zinc regulates the activity of enzymes (e.g., SOD), signaling pathways (MAPK, NF-κB), and transcription factors (MTF-1, Sp1) to maintain homeostasis. Both zinc deficiency (due to dietary insufficiency, malabsorption, or physiological stress) and zinc excess (from environmental pollution or feed oversupplementation) adversely affect health, disrupting mineral balance, enzyme function, and gut microbiota. In animal production, inorganic (zinc oxide, zinc sulfate) and organic (zinc methionine) sources of zinc increase growth, immunity, and productivity, although sustainable strategies are needed to mitigate environmental risks. Future research should focus on novel zinc formulations, precision nutrition, and interactions with gut microbiota to optimize livestock health and sustainable husbandry.