Although CH4 production increased throughout lactation irrespective of diet fed, the effect of fat supplementation on CH4 production was persistent. This persistency was also shown , although they only measured CH4 production up to week 16. showed that whole cottonseed caused a persistent reduction of CH4 production compared to control. In the study three different fat feeding strategies (brewers grains, hominy meal or cold-pressed canola and hominy meal) all reduced CH4 production, and in this study the inhibitory effect of supplementary fat persisted for at least 7 weeks, indicating that effect of fat on CH4 is persistent.