The alimentary stress induced significant increases of colonic total anaerobic bacteria, lactate-utilizing bacteria
and amylolytic bacteria concentrations. When horses were fed the 57% hay–43% barley diet, time spent in vigilance
tended to be positively correlated with cecal and colonic amylolytic bacteria concentrations during the sociability
test and with cecal lactate-utilizing and colonic amylolytic bacteria concentrations during the neophobia test.
These correlations suggested that dietary-induced modulation of the microbiota may affect horse behavior and
that behavioral cues may be used as non-invasive indicators of alimentary stress. It might prove useful to prevent
intestinal pain of horses on farm