at least one compound defined by one of the following formulae : ## str1 ## where x represents cl , br , ## str2 ## nhso 2 ch 3 , ## str3 ## or -- sch 3 , and n is 1 or 2 ; and ch . sub . 3 so . sub . 2 nhch . sub . 2 ch . sub . 2 cn have been administered to animals to improve the efficiency of food utilization by these animals . these compounds can be administered orally by combining the compounds with feed compositions and fed to animals such as ruminants with a developed rumen function as well as other animals that ferment fibrous material and vegetable matter in the cecum or colon . these compounds effect the rumen metabolism to increase the production of propionate relative to other volatile fatty acids , particularly acetate and to inhibit methanogenesis .