Aerobically stable diets can increase DMI of cattle. We evaluated the effect of 3 products (Alltech, Brazil) at 2 iso-propionic acid dosages on the aerobic stability of a 48.8% silage based TMR (50.5% DM, pH 5.52). Treatments were: Control (CTL), Mold-Zap 55 (55% propionic acid, 12% NH₄OH) at 0.5 (MZ55-L) and 1 (MZ55-H) L/ton, Mold-Zap Aquativa (25% propionic acid, 3% NH₄OH, and acids citric, sorbic, formic, lactic, and ascorbic) at 1.1 (MZAQ-L) and 2.2 (MZAQ-H) kg/ton, and Mold-Zap Aquativa Sorbato (35% propionic acid, 3% NH₄OH, 15% potassium sorbate, and acids citric and sorbic) at 0.8 (MZSO-L) and 1.6 (MZSO-H) kg/ton. Water (CTL) or products diluted in water (30 mL) were mixed to 5 kg of TMR and placed into six 30-L buckets/treatment. A bucket with each treatment was placed on one of 6 shelves in a controlled environment room (29.1 ± 1.7°C) for 48 h. The temperature of the TMR on each bucket and of the environment on each shelf were measured at 30-min intervals. Microbial counts (log cfu/g) were performed at 24 h. The statistical model contained the effects of shelf and treatment. Data obtained over time was analyzed as repeated measures. Contrasts compared CTL with other treatments. The maximum temperature (46.4°C) and the moment of maximum (1505 min) did not differ (P ≥ 0.15). The aerobic stability (moment of temperature of TMR + 2°C than environment) was increased by MZSO-H relative to CTL (830 vs. 710 min. P < 0.01) and trends (P ≤ 0.09) were detected for MZAQ-H (775 min) and MZSO-L (770 min). The mean temperature from 0 to 24 h was reduced (P ≤ 0.05) by MZ55-L (32.8°C), MZAQ-H (32.1°C), MZSO-L (32.4°C), and MZSO-H (31.5°C) relative to CTL (34.8°C), and trends (P = 0.06) were observed for MZ55-H (32.8°C) and MZAQ-L (32.9°C). The temperature from 24 to 48 h (44.0°C) did not differ (P ≥ 0.36). MZAQ-H and MZSO-L reduced (P ≤ 0.03) spore forming bacteria. Aerobic bacteria did not differ (P ≥ 0.34). Yeast was reduced (P ≤ 0.01) by MZ55-L, MZAQ-L, and MZSO-H and tended to be reduced (P = 0.06) by MZ55-H, MZAQ-H, and MZSO-L. Filamentous fungi were reduced (P < 0.01) by all treatments. The microbial growth inhibitors reduced TMR temperature from 0 to 24 h, yeast, and filamentous fungi. Product MZSO at the highest dosage was the most effective.