Production of greenhouse gases and odorous compounds from manure of beef feedlot cattle fed diets with and without ionophores

Authors: Spiehs, Mindy; Woodbury, Bryan; Hales Paxton, Kristin

Submitted to: Waste to Worth Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2019
Publication Date: 4/1/2019
Citation: Spiehs, M.J., Woodbury, B.L., Hales, K.E. 2019. Production of greenhouse gases and odorous compounds from manure of beef feedlot cattle fed diets with and without ionophores. In: Proceedings of Waste to Worth Conference, April 22-26, 2019, Minneapolis, Minnesota. Available: https://lpelc.org/production-of-greenhouse-gases-and-odorous-compounds-from-manure-of-beef-feedlot-cattle-fed-diets-with-and-without-ionophores/

Interpretive Summary:

Technical Abstract: Ionophores are a type of antibiotics that are used in cattle production to shift ruminal fermentation patterns. Ionophores do not kill bacteria, but inhibit their ability to function and reproduce. In the cattle rumen, acetate, propionate, and butyrate are the primary volatile fatty acid produced. It is more energetically efficient for the bacteria to produce acetate and use methane as a hydrogen sink rather than propionate. Ionophores inhibit archaea forcing bacteria to produce propionate and butyrate as hydrogen sinks rather working symbiotically with archaea to produce methane as a hydrogen sink. Numerous research studies have demonstrated performance advantages when ionophores are fed to beef cattle, but few have considered potential environmental benefits of feeding ionophores. The objectives of this study were to determine the methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O), odorous volatile organic compounds (VOC), ammonia (NH3), and hydrogen sulfide (H2S) production from beef cattle manure when an ionophore was fed to finishing cattle. Four pens of feedlot cattle were fed an ionophore and four pens received no ionophore (n=30 animals/pen). Samples were collected six times over a two-month period. A minimum of 20 fresh fecal pads were collected from each feedlot pen at each collection. Samples were mixed within pen and a sub-sample was placed in a small wind-tunnel. Duplicate samples for each pen were analyzed. Total CH4 concentration decreased (4.3 ppm vs. 3.2 ppm; P< 0.01) when an ionophore was fed. Of the VOCs measured, only total sulfide concentration was lower (P < 0.01) for the manure from cattle fed the ionophore (145 ppm) compared to those not fed the ionophore (233 ppm). Ammonia, N2O, CO2, H2S, and all other odorous VOC were similar between the cattle fed the ionophore and those not fed the ionophore. The results only account for concentration of gases emitted from the manure and do not take into account any urinary contributions, but indicate little reduction in odors or greenhouse gases when ionophores are fed to beef finishing cattle.