37 Evaluation of Methane and Carbon Dioxide Production in Growing and Finishing Cattle Raised in Conventional or Confinement-based Herds

Cattle originating from 2 different herds were used during growing and finishing programs to evaluate differences in CH4 and CO2 production. The conventional (CONV) herd used spring calving, summer grass grazing, and winter corn residue grazing. An alternate (ALT) herd housed cows in confinement pens during summer, calved in summer, grazed cover crops in fall and grazed corn residue before returning to confinement pens in spring. Each herd had 4 groups of 20 cows. For 2 years calves from each herd were weaned at the same age and then fed ad libitum for a 120-d growing (GR) period and fed a forage-based diet (NEg 1.23 Mcal/kg). Cattle were then adapted to a grain-based finishing (FIN) diet (NEg 1.51 Mcal/kg) and fed until reaching 1.27 cm backfat. Both CH4 and CO2 were collected in two pen-scale chambers by collecting air samples continuously from each pen ambient air. Each group was evaluated in the pen-scale chambers for 5 days during both the GR and FIN phases. Data were analyzed using the MIXED procedure of SAS with day in barn as a repeated measure. Whether cattle originated from CONV or ALT had no impact (P > 0.25) on CH4 or CO2 production. Feeding GR resulted in greater (P < 0.03) CH4 than FIN in grams per day (125.4 vs 117.5), grams per kg of intake (16.1 vs 11.5), or g per kg of body weight (0.50 vs 0.24). Greater CO2 production was observed for FIN as compared to GR which is due to greater size and energy intake. Diet impacts CH4 more so than cow-calf production system cattle originate from.