Four steers were used in a 4 × 4 latin square experiment to assess comparative antimethanogenic effects of including bromochloromethane (BCM) (5.5 g once daily), unsaturated fat (corn oil), and saturated fat (tallow) at 5% in experimental diets. Basic dietary ingredients were citrus pulp and beet pulp plus hay. Average daily gain (ADG) and ruminal parameters including soluble carbohydrate and total volatile fatty acid (TVFA) concentrations, VFA’s percentages, and pH were measured. Only BCM proved significantly (P < 0.05) antimethanogenic. Maximal inhibition occurred 0–6 hr post-feeding, by 15 hr inhibition was reduced by 50% and absent at 24 hr. Ruminal TVFA, pH, and average daily gain were not significantly affected (P > 0.05) by CH4 inhibition, although average daily gain showed the following trend: BCM > saturated fat > unsaturated fat > control. Inhibition caused lower (P < 0.05) ruminal acetate, and higher (P < 0.05) propionate over 24 hr post-feeding, higher (P < 0.05) butyrate from 3–15 hr post-feeding, and consistent measurable quantities of valerate and isovalerate. Soluble CHO concentration was maximal 0–6 hr post-feeding.