|SHRECK, ADAM - Orise Fellow|
|Todd, Richard - Rick|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/21/2014
Publication Date: N/A
Technical Abstract: Supplementing protein to low quality forage diets increases forage intake and digestion by cattle, but effects on greenhouse gas (GHG) production are largely unknown. To test this, 23 British-cross steers were used in a three period crossover design to evaluate the effect of protein supplementation to low-quality forage on ruminal methane (CH4 ) and metabolic carbon dioxide (CO2) emissions, forage intake, and ruminal volatile fatty acid proportion. Steers were individually offered low-quality grass hay (3.9% crude protein) ad libitum and supplemented with (dry matter basis): no protein (CON), cottonseed meal (CSM; 0.29% of body weight (BW) daily) or dried distillers grains with solubles (DDGS; 0.41% of BW daily). Ruminal CH4 and metabolic CO2 fluxes were obtained 6.3 ± 1.6 times/steer daily using a GreenFeed unit (C-Lock Inc., Rapid City, SD). Forage intake increased (P < 0.01 ) 53.0% with protein supplementation; however, no difference (P = 0.14) was observed between CSM (5.82 kg/d) and DDGS (5.50 kg/d). Ruminal and metabolic CO2 (g/d) were greater (P < 0.01) for steers fed CSM (5,520) and DDGS (5,453) than for steers fed CON (4,895). Steers supplemented with CSM (204.9) had greater (P < 0.01) CH4 emissions (g/d) than DDGS (189.2), both of which were greater (P < 0.01) than CON (174.1). Methane emissions as a proportion of gross energy intake (Ym), were lower (P < 0.01) for DDGS (7.32%) and CSM steers (7.86%) than CON (10.18 %). The observed decrease in Ym was also supported by DDGS (3.60) steers having the lowest (P < 0.01) ruminal acetate:propionate ratio while CSM (4.89) was intermediate and CON (5.64) steers were greatest. Results of this study suggest that the common practice of supplementing protein to cattle consuming low-quality forage yields beneficial decreases in GHG emissions per unit of beef produced.