Oxalates
Foxtail millet forage contain oxalates (0.7% DM) (Hintz et al., 1991) and should not be fed to horses as the only source of roughage since it may have a laxative effect, cause excessive urination, and kidney and bone problems (Teutsch, 2009).
Nitrates
If foxtail millet has been severely stressed it may accumulate nitrates at levels toxic for livestock (Teutsch, 2009; Oelke et al., 1990).
Mycotoxins
In Argentina, a case of mycotoxicity (5% morbidity) was reported in heifers consuming foxtail millet hay from bales contaminated with Fusarium chlamydosporum (Rodriguez et al., 1997).