Hourly methane production in finishing steers fed at different levels of dry matter intake.

Methane (CH) loss from finishing cattle is important as it represents an energy loss that could be used for maintenance and growth, and CH is a greenhouse gas with a global warming potential 21 to 25 times that of CO. Our objectives were to determine hourly CH production from growing cattle fed diets differing in corn processing method (dry rolling or steam flaking) and wet distillers grains with solubles (WDGS) inclusion rate. Eight steers (195 kg ± 2.3 in Exp. 1 and 322 kg ± 3.7 in Exp. 2) were fed the following diets: 1) steam-flaked corn (SFC)-based diet with 0% WDGS (SFC-0); 2) SFC-based diet with 15% WDGS (SFC-15); 3) SFC-based diet with 30% WDGS (SFC-30); 4) SFC-based diet with 45% WDGS (SFC-45); 5) Dry-rolled corn DRC)-based diet with 0% WDGS (DRC-0); and 6) DRC-based diet with 30% WDGS (DRC-30). All hourly CH data were analyzed using the MIXED procedure of SAS. Individual animal was the experimental unit. The model included the fixed effect of h, diet, and the h × diet interaction. Hourly differences in CH were analyzed using repeated measures. There were numerous h × diet interactions and thus simple-effect means are presented. In steers fed DRC-0 or DRC-30 at 2-times maintenance, the greatest hourly CH emissions occur 6 h after feeding ( < 0.01) with a secondary peak between 10 and 11 h after feeding ( < 0.01). For cattle fed SFC-0, SFC-15, SFC-30, and SFC-45 at 2-times maintenance, all diets had peak CH emissions 5 and 6 h after feeding ( < 0.01), with a secondary CH peak for SFC-45 nine to 11 h after feeding ( < 0.01). Cattle fed all diets at a maintenance level of intake exhibited 1 peak in hourly CH production between 3 and 6 h after feeding ( < 0.01). All steers fed SFC-30 and SFC-45 had sustained CH production over several hours, irrespective of intake level. Steers fed SFC-45 produced more CH beginning 4 h after feeding ( < 0.01) and produced a greater amount of CH than any other treatment ( < 0.01). Methane production generally peaked 6 h after feeding irrespective of intake level or diet type. Additionally, when fed above a maintenance level of intake, a secondary peak in CH production was observed 9 to 11 h after feeding, and steers fed at a maintenance level of intake had only 1 peak in CH production in a 23-h period.