Including poultry fat (PF) at different dietary concentrations can increase caloric intake and reduce dry matter intake (DMI) under precision feeding conditions where diets are isocaloric and isonitrogenous. High fat intake may lead to reduction in fiber digestibility and inadequate fermentation. However, reduction of DMI as PF is incorporated into diets can provide similar energy to the animal limiting the negative effects associated with fat inclusion. We hypothesized that including PF at increasing dietary concentrations would reduce intake without compromising rumen fermentation and nutrient digestibility in continuous cultures. Treatments included 2 forage combinations, low (LF; 35% forage), and high (HF; 70% forage) and 4 diet with PF dietary concentration starting with a basal level of fat in the diet [3% fat (0% PF inclusion); 5% fat (2% PF inclusion); 7% fat (4% PF inclusion); and 9% fat (6% PF inclusion)]. Fermenters were randomly assigned to treatments in a 2 × 4 factorial design and ran for 4, 10 d periods. Data were analyzed using the MIXED procedure of SAS with repeated measures. The LF-group had higher DM, OM, and NDF digestibility coefficients (dC; P < 0.01). The DM, OM, NDF, and ADF dC increased linearly with PF inclusion. Mean culture pH and NH₃-N were lower in the LF vs HF. The inclusion of PF resulted in a linear increase on NH₃-N and a quadratic increase on pH. The total VFA concentration was higher in the LF. There was a reduction in acetate and butyrate and an increase in propionate concentrations with LF. The PF inclusion had a quadratic increase on total VFA (P = 0.02). There was a linear interaction effect on acetate, propionate, and butyrate. Acetate and butyrate increased in HF as PF increased and decreased in LF. Propionate decreased in HF as PF increased and increased in LF. The HF yielded higher A:P. There was a linear interaction effect on A:P (P = 0.05). The A:P increased in HF as PF increased and decreased in LF. These results suggest that increasing PF in precision fed LF or HF can alter rumen fermentation and improve digestibility.