The objective of the current study was to compare methane (CH4) production from the in vitro gas production system by incubating feeds either individually or as mixed total diet. Eleven diets varying in the forage to concentrate ratio were tested. The forages were tropical grass or corn silages and the concentrate mixtures consisted of soybean grain, soybean meal, corn grain, wheat bran, urea and minerals in different proportions. There were three replicates for each diet. Methane production was reported as weighted mean for individual feeds and total diet separately. The mean of CH4 production from total diet was 30.1 mL g-1 dry matter (DM) and 30.8 mL g-1 DM from the weighted mean of individual feeds. There was a weak correlation between weighted CH4 production from individual feeds and complete diet (r = 0.15). It can be concluded that individual feeds cannot be used as a proxy to estimate CH4 production from total mixed diets.