Effects of Microminerals on Performance and Metabolic Adaptation in Heat-Stressed Dairy Cows: A Review

This narrative review summarizes the role of microminerals in mitigating heat stress (HS) in dairy cows, with a focus on antioxidant defense, immune function, and metabolic regulation. A systematic literature search (2000-2025) in Scopus, Google Scholar, and PubMed included only studies conducted on dairy cows under HS. Evidence indicates that chromium, selenium, zinc, copper, cobalt, and combined micromineral supplements affect production performance, physiological responses, and overall health in heat-stressed dairy cattle. Chromium supplementation has been widely studied for its role in enhancing energy metabolism, contributing to increased dry matter intake (DMI), milk yield, and better heat tolerance. Selenium, as part of selenoproteins, supports antioxidant capacity, thermotolerance, and immune function, though its effect on milk yield remains inconsistent. Zinc helps antioxidant defense, reduces inflammation, and maintains calcium homeostasis, but its impact on production outcomes is unclear. Copper supports immune and antioxidant functions, with results influenced by dose, source, and animal physiological status. Cobalt, essential for vitamin B12 synthesis and rumen microbial activity, is linked to higher milk and milk fat production; however, excessive intake may impair milk protein synthesis. Multi-micromineral strategies show synergistic benefits, including improved milk composition, udder health, immune function, and reproductive performance under HS. Nevertheless, responses vary with mineral form, dosage, physiological stage, and environmental conditions. In conclusion, micromineral supplementation represents a promising nutritional strategy to alleviate HS in dairy cattle. Yet, variability in outcomes highlights the need for further research to define optimal dosing, clarify mineral interactions, and establish practical guidelines for sustainable productivity and animal welfare in heat-stressed systems.