Effect of Cobalt Chloride on Fermentation of Alfalfa and Smooth Bromegrass Hays by Horse Cecal Microorganisms.
Authors: Fehlberg Laura K, Lattimer James M, Drouillard James S, Douthit Teresa L
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Cobalt Chloride and Forage Fermentation in Horses Cobalt's role in equine fibre digestion remains poorly characterised, prompting researchers to investigate whether cobalt chloride supplementation influences microbial fermentation of common hay types. Using an in vitro fermentation model with cecal fluid from four cannulated horses, the team incubated alfalfa and smooth bromegrass hay with five cobalt doses (0–50 mg/kg dry matter) and measured gas production, volatile fatty acid (VFA) output, dry matter disappearance, and pH over 48 hours. Alfalfa proved significantly more digestible than bromegrass (29.2% versus 19.4% dry matter disappearance), and whilst cobalt influenced gas production in bromegrass cultures—with 5 mg/kg producing more gas than 50 mg/kg—it did not alter final pH, VFA concentrations, acetate:propionate ratio, or digestion rates in either forage type. These findings suggest that whilst cobalt may modulate microbial activity in specific substrates, supplementation at the tested doses is unlikely to meaningfully enhance fibre digestion or alter the short-chain fatty acid profile that influences equine energy metabolism, limiting the practical justification for cobalt as a digestive enhancer in hay-based diets.
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Practical Takeaways
- •Cobalt chloride supplementation did not improve fiber digestibility or fermentation efficiency in this in vitro model, suggesting limited benefit for horses consuming typical forage diets
- •Forage selection (alfalfa vs. bromegrass) has a much greater impact on cecal fermentation and digestibility than cobalt supplementation levels tested
- •Further in vivo research is needed before recommending cobalt chloride as a dietary additive to enhance fiber digestion in horses
Key Findings
- •Alfalfa hay showed significantly greater in vitro dry matter digestibility (29.2%) compared to smooth bromegrass hay (19.4%)
- •Cobalt chloride affected gas production in bromegrass cultures, with 5 mg/kg substrate DM producing more gas than 50 mg/kg, but had no effect on alfalfa cultures
- •Cobalt chloride had no significant effects on terminal pH, volatile fatty acid concentrations, or in vitro dry matter digestibility in either forage type
- •Forage type significantly influenced gas production, VFA production, and acetate:propionate ratio, with alfalfa producing greater fermentative responses than bromegrass