The effects of feeding ferric citrate on ruminal bacteria, methanogenic archaea, and methane production in growing beef steers

Authors: CLEMMONS, BROOKE - University Of Tennessee; SCHNEIDER, L - University Of Tennessee; MELCHIOR, E - University Of Tennessee; Lindholm-Perry, Amanda; HALES, KRISTIN - Former ARS Employee; Wells, James - Jim; Freetly, Harvey; HANSEN, S - Iowa State University; DREWNOWSKI, MARY - University Of Nebraska; HARTMAN, S - Iowa State University; MYER, PHILLIP - University Of Tennessee

Submitted to: Access Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2020
Publication Date: 2/1/2021
Citation: Clemmons, B.A., Schneider, L.G., Melchior, E.A., Lindholm-Perry, A.K., Hales, K.E., Wells, J., Freetly, H.C., Hansen, S.L., Drewnowski, M.E., Hartman, S.J., Myer, P.R. 2021. The effects of feeding ferric citrate on ruminal bacteria, methanogenic archaea, and methane production in growing beef steers. Access Microbiology. 3(1). Article 000180. https://doi.org/10.1099/acmi.0.000180.
DOI: https://doi.org/10.1099/acmi.0.000180

Interpretive Summary: Ruminants are a significant source of methane from domestic livestock animals. In cattle, methane production represents a loss in energy and a reduction in animal feed efficiency. Ferric compounds can reduce hydrogen gas available for methane production, and dietary ferric citrate was evaluated in growing beef steers as a potential mitigation strategy to reduce rumen methane production. Ferric citrate was added to steer diets at different levels, and the animals were studied for in vivo methane production and ruminal fluid microbial compositions. The addition of ferric citrate to the diet had no impact on the ruminal microbial communities, the concentrations of ruminal methanogens, and the ruminal methane production. Ferric citrate fed at dietary levels up to 750 mg/kg of diet on a dry matter basis appears to have little ability to reduce ruminal methane production in growing beef steers fed forage-based diets.

Technical Abstract: Methane produced by cattle is one of the contributors of anthropogenic greenhouse gas. Methods to lessen methane emissions from cattle have been met with varying success; thus establishing consistent methods for decreasing methane production are imperative. Ferric iron may possibly act to decrease methane by acting as an alternative electron acceptor. The objective of this study was to assess the effect of ferric citrate on the rumen bacterial and archaeal communities and its impact on methane production. In this study, eight steers were used in a repeated Latin square design with 0, 250, 500 or 750mg Fe/kg DM of ferric iron (as ferric citrate) in four different periods. Each period consisted of a 16day adaptation period and 5day sampling period. During each sampling period, methane production was measured, and rumen content was collected for bacterial and archaeal community analyses. Normally distributed data were analysed using a mixed model ANOVA using the GLIMMIX procedure of SAS, and non-normally distributed data were analysed in the same manner following ranking. Ferric citrate did not have any effect on bacterial community composition, methanogenic archaea nor methane production (P>0.05). Ferric citrate may not be a viable option to observe a ruminal response for decreases in enteric methane production.