Influence of Dietary Cobalt on Fiber Digestibility and Serum Cobalt and Cobalamin Concentrations in Horses.
Authors: LeCompte Lazić Rebecca Ashlee, Nielsen Brian D, Robison Cara I, Schott Harold C, Herdt Thomas H, Larson Connie K
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Whilst the 2007 National Research Council reduced the recommended cobalt requirement for horses from 0.1 to 0.05 ppm, preliminary evidence suggested that higher dietary cobalt might improve fibre digestion—a claim this 2024 study set out to test rigorously. Four geldings (averaging 503 kg) were fed diets containing 0.06, 0.7, 2.0, and 3.0 ppm cobalt over four consecutive 5-week periods in a controlled Latin square design, with researchers measuring faecal and urinary output to assess fibre digestibility and cobalt balance. Contrary to the hypothesis, supplementing cobalt—even at 3.0 ppm, fifty times the current recommendation—produced no effect on neutral detergent fibre, acid detergent fibre, or lignin digestibility; however, cobalt balance shifted from negative (at 0.06 ppm) to positive at higher intakes, and serum cobalt concentrations increased markedly with dietary supplementation, whilst serum cobalamin levels paradoxically declined slightly. For practitioners, these findings suggest that elevated serum cobalt observed in clinical cases likely stems from injectable cobalt solutions rather than feed fortification, and that increasing dietary cobalt as a means to enhance fibre digestion lacks scientific support, making current NRC recommendations appropriate for maintenance of adequate cobalt status without resorting to higher supplementation strategies.
Read the full abstract on PubMed
Practical Takeaways
- •Increasing dietary cobalt beyond the current NRC recommendation (0.05 ppm) does not improve fiber digestion in horses, so supplementation for digestive performance is not justified.
- •Elevated serum cobalt concentrations in horses are more likely from parenteral injections than from fortified feed alone, relevant when interpreting bloodwork after injectable supplement use.
- •High dietary cobalt may slightly suppress serum cobalamin levels; monitor cobalamin status in horses receiving cobalt supplementation, particularly those at risk for deficiency.
Key Findings
- •Cobalt supplementation (0.7 to 3.0 ppm) did not affect neutral detergent fiber, acid detergent fiber, or lignin digestibility in horses despite preliminary suggestions otherwise.
- •Serum cobalt concentration increased dose-dependently from 0.8 µg/mL (control) to 4.7 µg/mL (high treatment, 3.0 ppm dietary Co).
- •Serum cobalamin concentrations slightly decreased 6% with increasing dietary cobalt intake (p = 0.003), suggesting potential metabolic interference.
- •Cobalt balance was negative on control diet (0.06 ppm) but positive on supplemented diets, indicating increased cobalt retention with dietary enrichment.