<p>The early life gut microbial colonization in pre-weaning calves plays a pivotal role in shaping their health, growth, and productivity. This review delves into the dynamic changes of intestinal microbiota during early life, emphasizing key factors such as colostrum management, feeding strategies, roughage supplementation, and microbial interventions including probiotics, prebiotics, and fecal microbiota transplantation (FMT), and non-nutritional stressors that can shape the early life microbial colonization. We highlight the microbiota's critical functions in nutrient metabolism, immune development, gut barrier integrity, and gut-brain axis regulation. Additionally, the consequences of microbial dysbiosis on calf health and its long-term effects on production performance in beef and dairy cattle are discussed. While current research has provided valuable insights, understanding causal mechanisms remains a challenge. This review aims to guide practical strategies for targeted microbial management, offering a pathway to optimize early-life interventions for improved calf health and productivity.</p>