Choline may be degraded to trimethylamine and methane by ruminal microbes; however, its effects on ruminal fermentation are still uncertain. Due to its final degradation to methane, we hypothesized that unprotected choline chloride effects on ruminal fermentation would depend on dietary NDF concentration. We used 8 fermenters of a dual-flow continuous culture system in a 4x4 duplicated Latin-square with a 2x2 factorial arrangement; factors being: choline chloride supplementation (0 and 2.5 g/kg DM) and dietary NDF% (30 and 40). Resulting treatments were: 1) 30% NDF + choline; 2) 30% NDF, no choline; 3) 40% NDF + choline, 4) 40% NDF, no choline. Basal diets (30 and 40% NDF) were fed at 0800 and 1800, and choline chloride was supplemented 4 times/d. Each experimental period lasted for 10 d (7 d adaptation, 3 d sample collection). At 0, 1, 2, 4, 6, and 8 h post morning feeding, pH was measured and samples collected for diurnal kinetics analysis of pH, VFA, and NH₃-N. Also, one sample of pooled digesta effluents was collected before morning feeding for pooled daily VFA and NH₃-N concentrations. Main effects of choline supplementation (Cho), dietary NDF% (NDF), and their interaction (Cho*NDF) were tested for all response variables. Effect of time (h post morning feeding) was considered for diurnal kinetics and data analyzed as repeated measures. For molar proportions of VFA daily pool, a 1.6% reduction in acetate (P = 0.03) resulted from choline supplementation regardless of dietary NDF%. However; only when 30% NDF diet was fed, a 8.0% increase in propionate (P = 0.006), and decreases of 8.2% in isobutyrate (P = 0.02) and 0.22 units in acetate:propionate (P = 0.04) were observed as a result of choline supplementation. For molar proportions of VFA kinetics, addition of choline tended to decrease acetate:propionate in 0.12 units (P = 0.1); but propionate tended to increase 7.8% only when choline was added to 30% NDF diet (P = 0.09). Our results suggest that feeding unprotected choline chloride at 2.5 g/kg DM may enhance efficiency of VFA synthesis, particularly when supplemented to lower NDF diets.