From conception to weaning: a review of physiological development in beef calves and windows for nutritional and management interventions

The period from conception to weaning represents the most influential developmental window in the life of a beef calf. During this time, skeletal muscle fibers are formed, adipocyte hyperplasia is initiated, vital organs mature, the immune and respiratory systems develop functional competence, and the gastrointestinal tract and rumen undergo rapid structural and microbial organization. These processes are highly sensitive to maternal nutrition, environmental conditions, and early life management. This review synthesizes current knowledge on the developmental physiology of beef calves from conception to weaning, emphasizing the biological mechanisms underlying fetal and neonatal growth, the establishment of the microbiome, and the maturation of immune, respiratory, and gastrointestinal systems. Particular attention is given to identifying critical windows during which targeted interventions can exert lasting effects on growth, health, and carcass quality. Prenatal strategies including protein and energy supplementation, vitamin and mineral provision, and emerging epigenetic interventions using methyl donors are evaluated alongside postnatal strategies such as colostrum management, nutritional programming, creep feeding, early weaning, and preconditioning. Quantitative effects from key studies are integrated throughout to contextualize the magnitude of biological responses, and for each intervention the level of agreement among studies, main sources of heterogeneity, and unresolved questions were summarized. Collectively, the evidence demonstrates that interventions applied during specific developmental windows can meaningfully influence lifetime productivity, but responses vary with production environment, dam condition, and genetic background. A holistic approach that aligns biological opportunity with economic feasibility is essential for optimizing calf development in modern beef production systems.