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Title: Whole cottonseed supplementation improves performance and reduces methane emission intensity of grazing beef steers

Author
item BECK, MATT - Oklahoma State University
item THOMPSON, LOGAN - Oklahoma State University
item WHITE, JASON - Oklahoma State University
item WILLIAMS, GARRET - Oklahoma State University
item PLACE, SARA - Oklahoma State University
item Moffet, Corey
item Gunter, Stacey
item REUTER, RYAN - Oklahoma State University

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2018
Publication Date: 7/20/2018
Publication URL: https://handle.nal.usda.gov/10113/6472378
Citation: Beck, M., Thompson, L., White, J., Williams, G., Place, S., Moffet, C., Gunter, S.A., Reuter, R. 2018. Whole cottonseed supplementation improves performance and reduces methane emission intensity of grazing beef steers. Professional Animal Scientist. 34:339-345. https://doi.org/10.15232/pas.2018-01722.
DOI: https://doi.org/10.15232/pas.2018-01722

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 tall grass prairie between zero and 10 pounds per day increased average daily gain 0.1 pounds per day for each pound of whole cottonseed fed. Also, daily methane emissions were decreased with whole cottonseed supplementation and were least per unit of body weight gain at the 4.5 pound/day rate. Hence, these results suggest that if whole cottonseed supplementation is used to mitigate methane emissions relative to average daily gain, approximately 4.5 pounds per day is the optimal feeding rate when grazing tall grass prairie with stocker cattle.

Technical Abstract: The objective of this experiment was to determine the effect of whole cottonseed supplement on average daily gain and enteric methane production of steers grazing warm-season perennial forages. Steers (n = 18; initial body weight = 317 +/- 5.5 kilograms) were trained to use an in-pasture methane measurement device (GreenFeed system to measure methane emissions; C-Lock Inc., Rapid City, SD) for 3 weeks. Steers were stratified by adaptation-period use of the GreenFeed system and then received whole cottonseed in a range from 0 to 2.86 kilograms/day (as-fed) in individual feeders. Body weight was measured weekly before feeding. Total fat content of the diet (whole cottonseed + forage) at the greatest whole cottonseed intake was estimated to be 8.3%. Animal performance increased linearly as whole cottonseed intake increased (P = 0.02). Due to inadequate use of the GreenFeed system by the control steers, the 0 whole cottonseed level was excluded from further analysis. In supplemented steers, there was a quadratic relationship between daily methane production (grams of methane/animal/day) and whole cottonseed intake (P = 0.02), with a minimum at 1.86 kilograms of whole cottonseed/day. Emission intensity (grams of methane/kilogram of average daily gain) was less at moderate levels of whole cottonseed intake, and after 2.0 kilograms of whole cottonseed intake/day, emission intensity increased. This resulted in a significant quadratic relationship between emission intensity and whole cottonseed intake (P = 0.01). These results suggest that if whole cottonseed supplementation is used to mitigate methane emission relative to average daily gain, approximately 2.0 kilograms is the optimal dose.