Melatonin as a multifunctional modulator: emerging insights into its role in health, reproductive efficiency, and productive performance in livestock

Abstract

Melatonin, a pleiotropic hormone plays a vital role in enhancing livestock performance not only by regulating circadian rhythms but also by exhibiting antioxidant, immunomodulatory, and metabolic regulatory effects that collectively improve resilience, fertility, and productivity. Melatonin's synthesis is predominantly influenced by light exposure, with increased production in darkness; however, factors such as diet and health status further modulate its levels. By helping animals adapt to environmental stressors, melatonin boosts immune responses, mitigates chronic illnesses, and optimizes production efficiency. Its regulatory influence extends to the hypothalamic-pituitary-gonadal (HPG) axis, enhancing hormone secretion, synchronizing estrous cycles, and improving embryo viability. This results in improved reproductive outcomes through the protection of gametes, increased sperm motility, and enhanced oocyte quality, all of which benefit the fertilization process. Additionally, melatonin positively impacts productive performance, promoting muscle growth, development, and optimizing milk yield and composition through its interaction with metabolic and endocrine systems. As ongoing research continues to uncover its broader physiological effects, melatonin supplementation emerges as a promising approach to improving livestock welfare, productivity, and sustainability in modern animal husbandry.

Keywords: animal performance; antioxidant status; health; melatonin; production potential.

FIGURE 1

Melatonin effects on the microbiomes in the animal’s body, influencing gastrointestinal, immune, and reproductive functions.

FIGURE 2

Antioxidant activity of melatonin across various tissues. It plays a role in receptor-independent pathways that result in the formation of metabolites like cyclic 3-hydroxymelatonin (C3OHM), N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), and N1-acetyl-5-methoxykynuramine (AMK). In addition to its antioxidant effects, melatonin modulates inflammatory responses by targeting key regulators, including activator protein 1 (AP-1), hypoxia-inducible factor 1α (HIF-1α), Nrf2, and NF-κB. It also impacts apoptotic pathways by interacting with proteins such as B-cell lymphoma 2 (Bcl-2) and contributes to maintaining redox homeostasis by reducing the generation of ROS. This leads to an upregulation of antioxidant enzymes like SOD, GPx, and CAT, while decreasing MDA levels, an indicator of LPO. Due to its amphiphilic nature, melatonin can easily cross tissue barriers, enabling it to exert protective effects on organs such as the liver, kidneys, cardiovascular system, as well as the reproductive organs like the testicles and ovaries.

FIGURE 3

Mechanistic pathways of melatonin in reducing stress and enhancing physiological functions in livestock animals.

FIGURE 4

Role of Melatonin in Ovarian Function and Folliculogenesis in Livestock. Melatonin from circulation is taken up by the theca and granulosa cells of the follicle, where it interacts with its receptors, MT1R and MT2R, within the ovarian follicular fluid. This interaction stimulates the expression of LH and FSH mRNA, promoting hormone maturation and enhancing steroidogenic enzyme activities, such as those catalyzed by P450 aromatase, P450scc, and CYP17, which are responsible for synthesizing P₄ and E₂. During the process of follicular rupture, ROS are generated as a result of inflammatory reactions, leading to ovulation and further steroidogenesis, particularly the synthesis of P₄ in the CL through monooxygenase reactions. Melatonin acts as a free radical scavenger, mitigating ROS-induced oxidative stress by boosting antioxidant enzymes like SOD, GPx, and CAT. This reduces LPO and DNA damage, while balancing ROS levels and antioxidative activity. By regulating mitochondrial function and minimizing oxidative damage, melatonin supports healthy follicle development, ovulation, and improved ovarian function, preventing detrimental effects such as apoptosis and follicular atresia. Ultimately, melatonin promotes the maturation of a healthy ovum, enhancing reproductive efficiency.