To assess the effect on bacterial counts of a bedding material based on forest biomass used as compost bedded pack (CBP), 8 dry no pregnant Holstein cows were used. Animals were randomly assigned to 1 of 2 treatments (T) in a crossover design with 4 cows per treatment. Treatments were (1) CBP with forest biomass (CBP-FB), and (2) CBP with sawdust (CBP-S). The study was conducted between October 2016 and March 2017, in 2 periods (P1 = autumn; P2 = winter) of 11 wk with a 4-wk washout period between them. Cows were individually allocated in concrete floor (12.5 m²) pens filled at the beginning of each period with 30 cm of each bedding material. Aeration of CBP was made twice daily, and an average of 0.8 kg/m²/day of bedding material was added when humidity was greater than 60%. Bedding material was sampled at wk 11. Data were analyzed using the MIXED procedure of SAS. Model contained T, P, and T × P interaction as fixed effect, and cow as random effect. Temperature was significantly lower (P < 0.001) in CBP-FB (24.3°C) than in CBP-S (32.2°C). There was a significant T × P interaction in humidity (P < 0.001), which was greater in CBP-FB in P1, but greater in CBP-S in P2. No significant effects in total bacteria counts were found in bedding material. Klebsiella spp. was significantly greater (P < 0.01) in CBP-S, whereas Streptococcus spp., and yeasts and fungi were significantly greater (P < 0.05) in CBP-FB. There was a significant T × P interaction (P < 0.05) in coliforms at 37°C and 44°C, E. coli and Staphylococcus aureus, being greater in CBP-S in P1, but greater in CBP-FB in P2. In contrast, coagulase-negative staphylococci was greater in CBP-FB in P1, whereas it was greater in CBP-S in P2 (P < 0.01). Period was significant for temperature, other gram-negative bacteria, other Streptococcus spp., yeasts and fungi, and Bacillus spp. These results suggest that forest biomass does not work better than sawdust as CBP bedding material to control temperature and humidity. The effect of bedding material on bacterial counts was season-dependent except for Klebsiella spp., Streptococcus spp., and yeasts and fungi.