The relative abundance and prevalence (fraction of HCT recipients with at least 1 butyrogen present) of butyrogens after the onset of acute GVHD of the gut stratified by steroid responsive or refractory GVHD. All plots are rolling averages. P values from mixed-effects modeling from day 0 to +21 (with gray background) relative to the peak of acute GVHD symptoms. Black dashed line is the median value for healthy donors.