The potential benefit of corn dried distillers' grain (co)products (DDG) in the mitigation of methane production in cattle: An in vivo analysis

Abstract Text: Our preliminary in vitro study indicated that feeding high-fat diets may decrease methane (CH<sub>4) production by cattle. The objective of this study was to determine the impact of different levels of DDG on the digestibility of OM and the production of CH<sub>4 using two open-circuit respiration chambers at the Nutrition and Physiology Center, Texas A&M University, College Station, Texas. The respiration chambers monitored the inflow and outflow of CO<sub>2, O<sub>2 (fuel cell oxygen, FC-1B; Sable Systems, Henderson, NV), CH<sub>4, and water vapor continuously, and all calculations were corrected for the standard temperature and pressure of the air mass flowing through the chambers (FLOWKIT 500H; Sable Systems, Henderson, Nevada).Relative humidity was measured and used to calculate the dew point and water vapor pressure. Gases measurements were performed using a flow-through system (RH-100). Air from each source (chambers A and B, and baseline) were sampled every 4 min. The diets were formulated to have same level of ME (Mcal/kg) and to contain 0, 20, or 40% of DDG (DM basis). Animals were adapted to the experimental diets for 7 d outside the chambers and then brought in for a 48-h period for consecutive gas exchange measurement. The intake was restricted to 2% of BW and fed twice daily. Six Angus steers were allocated in an incomplete Latin rectangle design (2 animals/diet for 3 periods). The R software (R Core Team, Vienna, Austria) and PROC MIXED of SAS (SAS Inst., Cary, NC) were used to analyze the data using a repeated measure design. Diets were assumed to be fixed factors and periods and animals were random factors. The analysis of CH<sub>4 emissions (L/d) corrected for a 24-h period and the CH<sub>4 adjusted to BW (L/kg/d) had significant (<i>P</i> = 0.0081) linear and nonlinear decay patterns between CH<sub>4 emissions and levels of DDG. Although the 20 and 40% DDG levels (DM basis) did not differ in reducing CH<sub>4 emissions (<i>P</i> = 0.16), the linear relationship showed that for each percentage unit increase in DDG (DM basis) in the diet, a decrease (<i>P</i> = 0.0027) of 0.005 L/kg of BW/d of CH<sub>4 emissions was observed. We concluded that 20% of DDG (DM basis) is sufficient to promote a significant reduction in CH<sub>4 emission by cattle receiving DDG.

Keywords: abatement, greenhouse gas, respirometry