An energy and monensin supplement reduces methane emission intensity of stocker cattle grazing winter wheat

Authors: THOMPSON, LOGAN - Oklahoma State University; BECK, MATTHEW - Oklahoma State University; Gunter, Stacey; WILLIAMS, GARRET - Oklahoma State University; PLACE, SARAH - Oklahoma State University; REUTER, RYAN - Oklahoma State University

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2019
Publication Date: 8/1/2019
Citation: Thompson, L.R., Beck, M.A., Gunter, S.A., Williams, G.D., Place, S.E., Reuter, R.R. 2019. An energy and monensin supplement reduces methane emission intensity of stocker cattle grazing winter wheat. Applied Animal Science. 35:433-440. https://doi.org/10.15232/aas.2018-01841.
DOI: https://doi.org/10.15232/aas.2018-01841

Interpretive Summary: Methane emissions from ruminal fermentation of feedstuffs within animals are a significant source of the agricultural methane emissions. These emissions are of interest because of the role methane plays as a potent greenhouse gas and because methane emissions represent an inefficiency within the animal production system. When feedstuffs are consumed a portion is converted to methane, as the portion converted to methane increases the retained energy to consumed energy ratio decreases and the system is less efficient. For this reason, there is significant interest in reducing methane emission by ruminant livestock. Research in cooperation between Oklahoma State University and the Southern Plains Range Research Station has shown that supplementing cattle grazing wheat pasture between zero and 2.5 pounds per day increased average daily gain at a diminishing rate for each pound of corn meal fed. Also, total daily methane emissions were increased with corn meal supplementation but methane emission per unit of body weight gain was decreased as supplement intake was increased. These data suggest that if corn meal supplementation is used to mitigate methane emissions relative to average daily gain, as corn meal supplementation is increased the methane yield per unit of body weight gain is decreased with stocker cattle grazing wheat pasture.

Technical Abstract: The objective of this study was to determine the effect of an energy supplement with monensin on methane emissions and performance of stocker calves grazing winter wheat. Eight steers (initial body weight = 262 ± 33 kg) and 8 heifers (initial body weight = 240 ± 21 kg) were grazed in a 9-ha winter wheat pasture and methane emissions were recorded. Calves were the experimental unit and were randomly assigned within sex to receive 0, 0.21, 0.43, 0.64, 0.86, or 1.07 kilograms of a supplement (as-fed, primarily ground corn, wheat midds and 34 milligrams/kilograms of monensin) per day. Animals were supplemented 3 days per week in individual stalls and orts were weighed. Forage intake was estimated with titanium dioxide as an external marker. As several independent variables were available, dependent variables of interest were subjected to backwards stepwise regression with baseline methane, total supplement intake, forage intake, initial body weight, sex, and monensin dose in the model. Animal performance increased quadratically with increased total supplement intake and forage intake (probability < 0.02). Supplement intake quadratically reduced forage intake (probability < 0.01) with initial body weight and sex in the model. Methane emissions increased with increasing forage intake and initial body weight, but heifers produced less methane than steers (probability < 0.01). Supplement intake reduced methane emission intensity (grams of methane/kilograms of body weight gain; probably = 0.03) quadratically with baseline methane included in the model. These results suggest that supplementing cattle grazing wheat pasture with an monensin-containing energy supplement improves sustainability.