Impact of source of sulfur on ruminal hydrogen sulfide and logic for the ruminal available sulfur for reduction concept

Effects of organic and inorganic sources of S on intake, intake pattern, ruminal pH, VFA profile, and ruminal H2S gas concentration ([H2S]) were evaluated, which lead to development of a procedure to measure ruminal S availability for reduction [ruminal available S (RAS)] as well as compare with an estimated number [adjusted ruminal protein S (ARPS)]. Ruminally cannulated crossbred beef steers (n = 5; BW = 548 ± 46 kg) were assigned to 1 of 5 diets in a 5×5 Latin square design and fed ad libitum in five 21-d periods. Steers were fed a dry-rolled corn diet (CON), inorganic S source (ammonium sulfate; INORG), organic S source (corn gluten meal) fed at 9.8 (ORG-L) or 23% of diet DM (ORG-H), or wet distillers grains with solubles (WDGS) fed at 50% of diet DM. For the laboratory procedure, individual ingredients were incubated with ruminal fluid from heifers fed 60% corn-based diets (n = 2) and McDougall’s buffer. Bottles were cooled in ice, centrifuged, and decanted, and the precipitate w