The transition period, spanning approximately three weeks before and after parturition, represents one of the most critical physiological windows in dairy production. Profound metabolic, endocrine, and immune adaptations occur as the cow shifts from gestation to lactation, predisposing high-yielding cows to oxidative stress, inflammation, and metabolic imbalance. Negative energy and metabolisable protein balances stimulate extensive lipolysis and the accumulation of non-esterified fatty acids (NEFAs) and β-hydroxybutyrate (BHBA), which can impair hepatic function and postpartum performance. This review integrates recent advances in the understanding of metabolic and immunometabolic regulation during transition, emphasising the interplay among energy metabolism, oxidative stress, and immune dysregulation. It critically re-evaluates current nutritional interventions including controlled-energy and negative DCAD diets, rumen-protected polyunsaturated fatty acids, and methyl donor amino acids while highlighting the emerging potential of injectable trace minerals as adjunct strategies to improve metabolic resilience. The review concludes by outlining remaining knowledge gaps and proposing a framework linking physiological mechanisms with targeted nutritional management.

Injectable trace mineral supplementation (ITMS) has been proposed to support physiological adaptation during critical stages in dairy cattle; however, field-based evidence from pasture-based seasonal-calving systems remains limited. This study evaluated the effects of ITMS, administered at birth in calves and approximately 30 days before fixed-time artificial insemination in early-lactation cows, primarily on erythrocyte glutathione peroxidase activity and plasma trace mineral concentrations, while health, growth, production, and fertility were monitored as secondary outcomes. Thirty newborn calves receiving isotonic saline control (CNTRL; n = 15) or ITMS (n = 15) and 50 early-lactation cows (CNTRL, n = 24; ITMS, n = 26) were enrolled. In calves, erythrocyte glutathione peroxidase activity was higher in ITMS calves (322 vs. 359 U/g Hb; p < 0.01), and plasma selenium was higher on day 15 (0.57 vs. 0.62 µmol/L; p = 0.03). A treatment × week interaction was detected for body weight, but overall body weight and average daily gain did not differ. In cows, plasma selenium was transiently higher in multiparous ITMS cows on day 15 (1.04 vs. 1.09 µmol/L; p = 0.03), while antioxidant and inflammatory biomarkers, production, mastitis incidence, and fertility were unaffected. Overall, a single ITMS administration elicited modest biochemical and selenium responses without statistically detectable improvements in growth, health, production, or fertility.