High aerobic stability was found in TMR silage regardless of bacterial inoculant and ensiling period. This resistance was also shown previously in untreated TMR silage, although the stability test was conducted only at 60 d of ensiling, when yeasts were reduced to undetectable level (Nishino et al., 2003b). In this study, the stability was shown even when about 106 cfu/g of yeasts remained and appeared to be unrelated to the profile of fermentation that varied with inoculation of L. casei. Evidence has shown that silages with more than 105 cfu/g of yeasts are prone to deteriorate on exposure to air (McDonald et al., 1991). This criterion could account for the results of corn silage, but apparently did not suit the results of TMR silage stored for 10 d.