We determined the effects of supplementing chitosan, a natural biopolymer, on ruminal metabolism and in situ degradability in beef steers consuming hay. Eight ruminally cannulated crossbred steers (345 ± 81 kg BW) were used in a crossover design. Steers were stratified by weight and randomly assigned to 1 of 2 treatments: control (CTRL; no chitosan supplementation) or treatment (TRT; 80 g/d of chitosan). Chitosan was dosed daily via ruminal cannula and steers had ad libitum access to Tifton 85 bermudagrass hay and water throughout the study. Ruminal fluid was collected before dosing of chitosan (0 h) and every 3 h post-dosing for 24 h. Immediately after each collection, ruminal pH was measured. Ruminal fluid was analyzed for VFA and NH₃-N concentrations. Data were analyzed as repeated measures and the model included the fixed effects of treatment, time, and treatment × time interactions. In situ degradability of DM, NDF, and ADF was determined by incubating Tifton 85 bermudagrass hay in nylon bags within the rumen for 24, 48 or 72 h. Supplementing with 80 g/d chitosan had no effect (P > 0.05) on ruminal in situ degradability of DM, NDF or ADF. Chitosan did not affect (P = 0.97) NH₃-N concentrations (7.4 ± 0.58 mM) within the rumen. A treatment × time interaction was observed (P < 0.001) on ruminal pH. A treatment × time interaction (P = 0.016) was observed for acetate-to-propionate ratio (A:P), being decreased (P < 0.05) at h 21 and 24 for TRT vs. CTRL. Molar proportions of acetate and propionate had a treatment × time interaction (P < 0.05). Molar proportions of propionate were increased at h 18, 21 and 24 for TRT when compared with CTRL. Supplementing 80 g/d of chitosan to steers consuming ad libitum hay had no effect on in situ ruminal degradability; however, VFA molar proportions were shifted to an energetically more efficient composition by increasing propionate and decreasing A:P.