Postnatal Development of Prospective Beef Bulls: Integrating Nutrition, Metabolism, Endocrine Regulation, and Breeding Soundness.

Postnatal development in developing beef bulls is regulated through coordinated interactions among nutritional, metabolic, endocrine, and physiological processes that collectively determine structural maturation, reproductive competence, and breeding soundness. Optimizing these integrated regulatory mechanisms is essential for improving reproductive efficiency, accelerating genetic gain, and enhancing the sustainability of beef production systems. This review synthesizes current knowledge on the integrated regulation of postnatal development in developing beef bulls by combining evidence from developmental physiology, nutrition, metabolism, endocrine regulation, and reproductive biology. Particular emphasis is placed on tissue-specific maturation, nutrient-sensing and endocrine signaling, metabolic adaptation, developmental nutrient partitioning, pubertal development, and the biological mechanisms underlying breeding soundness. The review further evaluates practical approaches for assessing developmental progress using growth and structural traits, metabolic and endocrine biomarkers, reproductive indicators, and breeding soundness evaluation while highlighting the emerging roles of precision nutrition, precision phenotyping, multi-omics, wearable sensor technologies, artificial intelligence, and predictive modelling in developmental management. Current evidence indicates that postnatal development is governed by integrated biological networks rather than isolated physiological processes. Adoption of systems biology and data-driven approaches will facilitate earlier prediction of developmental competence, enable precision management of replacement sires, and improve reproductive efficiency, genetic progress, and the long-term sustainability of beef production.