Leptin in Dairy Cows: Metabolic Adaptation, Reproductive Function, and Health Applications

Leptin (LEP) is an adipocyte-derived cytokine that integrates nutritional status, metabolism, and reproduction in cattle, with particular relevance for modern high-producing dairy cows. In ruminants, LEP and its receptors are widely expressed in metabolic and reproductive tissues, including adipose tissue, liver, hypothalamus, pituitary, ovary, uterus, and placenta, where LEP modulates energy homeostasis, neuroendocrine function, and local tissue responses. Changes in circulating LEP concentrations during the transition period reflect changes in body fat reserve, insulin and GH-IGF-1 dynamics, thyroid hormones, and inflammation and contribute to coordinated metabolic adaptations supporting the onset of lactation. At the reproductive level, LEP influences the hypothalamic-pituitary-gonadal axis, affects the pulsatility of luteinizing hormone (LH) under nutritional stress, and exerts direct effects on ovarian steroidogenesis, folliculogenesis, oocyte competence, embryo development, and uterine immune function. New evidence also links LEP profiles to major peripartum disorders, including subclinical ketosis, insulin resistance, postpartum ovarian inactivity, and uterine inflammatory diseases, and emphasises its potential as part of a panel evaluating the risk of metabolic and reproductive disorders. Furthermore, polymorphisms within the bovine LEP gene and its signalling network have been associated with milk production, feed efficiency, body condition, and fertility traits, suggesting opportunities to incorporate markers into genomic selection schemes aimed at improving robustness and reproductive performance. This review summarises current knowledge on LEP biology in cattle, with an emphasis on dairy cows, and discusses perspectives on translating this information into practical tools for nutritional management, health monitoring, and genetic improvement in bovine production systems.