Reproductive success drives cattle enterprise profitability, and trace minerals play a pivotal role in both bulls and cows. Copper, zinc, selenium, manganese, and chromium influence fertility, embryo viability, and metabolic resilience. Strategic supplementation — especially during pre-breeding, gestation, and stress periods — can correct deficiencies, optimise reproductive outcomes, and enhance herd performance. Injectable formulations offer precise, rapid support under veterinary guidance, improving conception rates and herd profitability.
Reproductive performance drives profitability in cattle enterprises, with nutrition playing a central role alongside genetics and disease control. Adequate nutrition influences conception rates, calving patterns, and pre-weaning growth. In breeding bulls, it affects testicular development, puberty onset, sperm quality, and acrosomal integrity. Trace minerals (TM) are particularly vital for reproductive function, immune competence, and metabolic efficiency.1-6
This article explores the physiological roles of TM in reproduction, reviews evidence-based supplementation strategies, and outlines targeted injectable approaches for managing confirmed deficiencies to enhance reproductive outcomes in both beef and dairy systems.
TM deficiencies increasingly observed in cattle herds
Deficiencies in TM — including copper (Cu), zinc (Zn), selenium (Se), manganese (Mn), and chromium (Cr) — are increasingly observed in cattle herds. Contributing factors include declining mineral concentrations in soils, forages, and feedstuffs, as well as variations in age, production stage, and elevated physiological demands during reproduction, gestation, and lactation.2,3
Timing breeding for grass, growth and gross margin
In South Africa, cattle breeding seasons are scheduled to align with environmental conditions and pasture availability, making strategic nutrition crucial for reproductive success. Summer breeding is generally preferred in summer rainfall areas, while winter breeding is only viable if sufficient high-quality feed is available, often to mate earlier-maturing heifers at 18- to 21-months.
However, according to Bergh, two breeding seasons per year can benefit herds by reducing the interval for non-pregnant cows, allowing earlier heifer mating, and improving bull utilisation, but require greater management effort and may dilute selection pressure and performance testing.1
The advantage of winter breeding is lower parasite loads for pre-weaning calves and typically higher weaner prices, but cows often have poorer condition, necessitating additional supplementation to meet peak nutritional demands. Optimal breeding season length is critical: Lactating cows should have a 65-day season (three cycles), and heifers or dry cows 45-days (two cycles), ensuring conception within ~80 days post-calving to maintain annual calving synchrony.1
Physiological roles of TM in reproduction
Copper: Energy and antioxidant support
Cu functions as a cofactor for cytochrome oxidase in mitochondrial adenosine triphosphate production, Cu-superoxide dismutase (SOD) antioxidant defense, and ceruloplasmin for inflammation regulation. The mineral supports cellular respiration, oocyte and embryo viability, and fetal connective tissue and neurological development. Higher copper concentrations have been linked to improved corpus luteum function and pregnancy outcomes, demonstrating the mineral’s importance in reproductive success.2
Zinc: The foundation mineral
Zn serves structural and catalytic roles in numerous enzymes and transcription factors, particularly Zn finger proteins essential for steroid receptor DNA binding. As a component of Zn-SOD antioxidant enzyme, Zn protects oocytes and embryos from oxidative damage during critical developmental periods. The mineral supports endometrial and mammary epithelial integrity, immune cell proliferation, and appetite regulation, directly affecting dry matter intake and energy balance.2
Research has documented associations between higher Zn concentrations, greater antioxidative capacity through SOD and glutathione peroxidase (GPx) activity, and improved corpus luteum function with higher progesterone levels and enhanced pregnancy outcomes at timed artificial insemination. The ‘Zn spark’ phenomenon at fertilisation represents a conserved mechanism across mammalian species, implicating Zn in oocyte activation and polyspermy prevention, directly affecting embryo quality.2
Selenium: Antioxidant protection
Se serves as a component of seleno-proteins including GPx, deiodinases, and thioredoxin reductase, providing protection against peroxide-mediated damage and lipid peroxidation. X-ray fluorescence imaging has revealed selenium concentration within granulosa cells of large follicles, where it upregulates GPx-1 expression, suggesting a protective antioxidant role during follicular development.2
Clinical studies have demonstrated that Se supplementation improves post-partum uterine involution, reduces retained foetal membranes, and decreases incidence of metritis and mastitis. The mineral’s role in supporting granulosa cell proliferation and estradiol production directly impacts reproductive efficiency.2
Manganese: Enzymatic support and steroidogenesis
Mn functions as a cofactor in Mn-SOD, arginase, pyruvate carboxylase, and enzymes responsible for glycosaminoglycan synthesis, particularly chondroitin sulfate important for skeletal and foetal development. The mineral’s involvement in steroidogenesis through cholesterol synthesis supports corpus luteum function and early embryo viability.2
Research also indicates that Mn and Mn-SOD are actively transcribed in cumulus-oocyte complexes and pre-implantation embryos. Dietary targets of ~15.8mg Mn/kg dry matter have been established for growth and reproduction, though higher demands during pregnancy may require adjusted supplementation strategies.2
Chromium: Metabolic and stress modulation
Cr plays an important role in metabolic regulation and immune function, particularly during periods of stress such as those experienced by feedlot cattle. It enhances the action of insulin and insulin-like growth factor I in tissues including muscle and liver, supporting glucose metabolism, growth, and metabolic homeostasis. Cr supplementation has also been associated with reduced circulating cortisol concentrations under high-stress conditions. Immunologically, Cr exerts dose-dependent effects.3
At appropriate levels, it stimulates lymphocyte proliferation, enhances cell-mediated immunity, and supports antibody production following vaccination. However, excessive concentrations may exert inhibitory effects. In cattle, Cr has been shown to modulate cytokine responses and improve immune competence, highlighting its potential value in stress management and overall health maintenance.3
Bull fertility and trace mineral status
TM status has a significant impact on reproductive development in breeding bulls, influencing testicular growth, onset of puberty, sperm quality, and acrosomal integrity. Supplementation has been associated with earlier puberty and improved semen characteristics in growing bulls, with liver mineral concentrations correlating positively with semen quality markers. Zn deficiency, in particular, impairs testicular development and spermatogenesis, with supporting evidence from bovine, ovine, and human studies demonstrating the benefits of adequate Zn status.6
A large American study involving 488 bulls (~7 months old) evaluated injectable TM supplementation. Bulls receiving injectable TM showed improved sperm motility and morphology. While overall breeding soundness exam pass rates at 12-months did not differ, a greater proportion of injectable TM-treated bulls that initially failed at nine-months passed at 12-months compared with controls. Marginal plasma Zn levels were noted, reinforcing Zn’s critical role in achieving breeding soundness.6
Strategic supplementation approaches
Effective supplementation strategies should be diagnosis-driven, aligning mineral form, dosage, and timing with physiological demands and production stage. Critical intervention windows include the pre-breeding period to support follicular development and oocyte competence; the transition phase to enhance immune and metabolic resilience. Late gestation to optimise fetal mineral transfer; and high-stress events such as weaning and transport.3
Injectable TM formulations offer particular advantages in beef production systems. They deliver a precise, controlled dose that bypasses potential dietary antagonists and variability in intake. Following administration, these minerals are rapidly absorbed and effectively stored, providing predictable support during periods of increased reproductive or metabolic demand.3
Micromin B is an injectable multi-mineral veterinary medicine formulated for cattle to prevent, maintain, or correct diagnosed deficiencies of Cu, Zn, Mn, Se and Cr. The product contains specific concentrations per milliliter: Cu 7.5mg, Zn 40mg, Se5mg, Mn 10mg, and Cr 5mg.4
The product requires weight-based dosing with calves (25-250kg) receiving 1ml per 50kg body weight subcutaneously, while adult cattle (>250kg) receive 1ml per 100kg body weight subcutaneously. Administration occurs exclusively via subcutaneous injection in the side of the neck, requiring sterile equipment and professional veterinary supervision.4
Safety considerations
Contraindications include use in species other than cattle, animals in poor body condition, those showing jaundice or liver dysfunction, and situations where Cu and Se status remain unknown due to toxicity risks. The product must never be mixed with other vaccines or medicines, and handlers require personal protective equipment to avoid exposure.4
Expected side effects include brief local irritation lasting ~30 seconds and slight swelling that may persist for several days. Serious risks involve Cu and Se toxicity if administered to animals with adequate mineral levels, emphasising the importance of diagnostic testing before treatment.4
Practical implementation
The product offers zero-day withdrawal periods when used as directed, allowing immediate resumption of production. Storage requires temperatures at or <25°C with protection from sunlight and freezing, while opened vials must be used completely without storage for future use.4
Economic considerations and production outcomes
Strategic TM supplementation, while involving direct costs, provides returns through higher conception and pregnancy rates, reduced embryonic losses, decreased disease incidence including metritis and mastitis, improved immune responses and vaccine efficacy, enhanced growth rates and feed conversion, improved carcass and milk quality, reduced veterinary treatment costs, and extended productive life of breeding stock.4
Cost-effectiveness increases through strategic timing during pre-breeding, transition, late gestation, and stress periods, with regular monitoring and follow-up testing optimising treatment success and herd management plans.4
Implementation recommendations
Successful implementation requires identifying production problems or risk periods, diagnosing herd mineral status through appropriate testing before treatment, reviewing forage and soil mineral analyses for antagonists and seasonal variations, selecting appropriate supplementation strategies based on diagnosis and required speed of action, administering treatments under veterinary supervision following label instructions, monitoring animals and conducting follow-up testing to evaluate success, and integrating mineral strategies with comprehensive nutrition, body condition management, disease control, and bull fertility programmes.4
Conclusion
TM supplementation represents a critical component of comprehensive cattle reproductive management, with strategic interventions during critical physiological windows offering significant potential for improved outcomes. The availability of targeted injectable formulations such as Micromin B provides veterinarians with tools for rapid correction of diagnosed deficiencies when oral supplementation may prove insufficient or impractical. Success requires commitment to diagnostic testing, professional veterinary oversight, and integration with broader herd management strategies. When implemented appropriately, evidence-based trace mineral supplementation contributes to enhanced reproductive performance, improved animal health, and increased enterprise profitability.
References
- Bergh L. Breeding seasons – Management tool for increased efficiency. 2019 [Internet]. Available at: https://bonsmara.co.za/wp-content/uploads/2019/03/Chapter-7.pdf
- Palomares R, Ferrer M, Jones L. Role of trace minerals in cow’s reproductive function and performance: A clinical theriogenology perspective. Clinical Theriogenology, 2024. Available at: http://bit.ly/3OBjHQE.
- Palomares RA. Trace Minerals Supplementation with Great Impact on Beef Cattle Immunity and Health. Animals, 2022. Available at: https://www.mdpi.com/2076-2615/12/20/2839
- Professional Information. Micromin B. 2024 [Internet]. Available at: https://designbio.co.za/wp-content/uploads/2024/06/Micromin-B-Package-insert_compressed.pdf
- Fontes P. 26 Trace minerals to improve bull fertility. J Anim Sci, 2024 Sep 13;102(Suppl 3):82–3. doi: 10.1093/jas/skae234.092. PMCID: PMC11400491. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC11400491/#:~:text=The%20article%20discusses%20the%20importance%20of%20bull,and%20manganese%20can%20lead%20to%20earlier%20puberty
- Arthington JD, Ranches J. Trace mineral nutrition of grazing beef cattle. Animals (Basel), 2021. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC8532955/