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Effect of cobalt chloride on fermentation of alfalfa and smooth bromegrass hay by equine cecal microorganisms
L. K. Fehlberg, J. M. Lattimer, J. S. Drouillard†, and T. L. Douthit
Microorganisms require Cobalt to synthesize vitamin B12, an important coenzyme in energy metabolism. It is suggested that increasing Co above requirements may increase fiber digestibility in bovines; however, effects of Co on cecal microorganisms in equines are unknown. Our objective was to evaluate in vitro effects of Co chloride on in vitro gas production, VFA production, and IVDMD using cecal fluid from four cannulated Quarter Horses as inoculum. Alfalfa or smooth bromegrass hay were provided as substrates with 0.0, 0.5, 5.0, 25.0, or 50.0 mg Co/kg substrate DM. Fermentation bottles containing 10 mL of equine cecal fluid and 140 mL of McDougall’s buffer were incubated in duplicate, and pH, VFA concentrations, and IVDMD were measured after 48 h of fermentation. Gas production was measured every 15 min during the fermentation period. Terminal pH was not affected by Co or forage type (P > 0.19). There was greater IVDMD in cultures containing alfalfa (29.2%) compared to smooth bromegrass hay (19.4%; P < 0.01). There was a forage × Co interaction in which gas production was greater in cultures containing alfalfa compared to brome and 5 mg Co/kg substrate DM was greater than 50 mg Co/kg substrate DM in cultures containing brome (P < 0.05). Gas production was also affected by forage, Co, and time (P < 0.01). Production of acetate, propionate, butyrate, isobutyrate, isovalerate, and total VFA, as well as acetate:propionate (A:P) ratio, were increased in cultures containing alfalfa compared to those containing brome hay (P < 0.05). Cobalt influenced in vitro gas production in smooth bromegrass hay by mixed cecal microorganisms; however, effects were not observed in pH, VFA, nor IVDMD regardless of substrate source.