Adaptation To Various Sources Of Dietary Sulfur By Ruminants

The objective of these experiments was to determine adaptation by ruminants to dietary sulfur. In Exp. 1, lambs (n = 54; BW = 33.6 +/- 0.4 kg) were allotted to 3 treatments: 1) 0% added dietary S (0%S), 2) 0.2% added dietary S (0.2%S), or 3) 0.4% added dietary S (0.4%S). Sulfur was added to the diet as Na2SO4. Lambs fed the 0.2%S and 0.4%S diets had greater (P < 0.01) ADG and G:F compared to those fed the 0%S diet. There was time x diet interaction (P < 0.01) on ruminal hydrogen sulfide gas (H2S) concentrations. Ruminal H2S was not detected in lambs fed 0%S at any time. Ruminal H2S were not affected (P > 0.19) by diet on d 1 or 8; however, H2S were greater (P < 0.01) for lambs fed 0.2%S and 0.4%S than for lambs fed 0%S on d 15, 22, and 29 (0.2% was 931, 846, and 1,131 mg/L and 0.4% was 975, 737, and 1,495 mg/L on d 15, 22, and 29, respectively). These data suggest it takes at least 29 d for peak ruminal H2S to occur after exposure to Na2SO4. In Exp. 2, lambs (n = 66; BW = 51.1 +/- 0.4 kg) were allotted to 3 treatments: 1) 60% dried distillers grains with solubles (DDGS), 2) corn-based diet with Na2SO4, or 3) corn-based diet with H2SO4. All diets were formulated to contain 0.4%S. Lambs fed Na2SO4 had greater (P < 0.05) ADG, DMI, and G:F than those fed H2SO4 or 60% DDGS. A time x diet interaction occurred (P < 0.01) for ruminal H2S. There was no difference (P = 0.82) in H2S of lambs on d 1. However, at d 14 and 27 lambs fed supplemental Na2SO4 had the lowest H2S concentrations while lambs fed 60% DDGS had the greatest (P < 0.01 on both d); lambs fed H2SO4 were intermediate and different than both. These data suggest that at the same dietary S concentration, acidic S sources increased H2S and decreased DMI and ADG. In Exp. 3, Angus cross calves (n = 72; average initial BW = 324 +/- 3 kg) were allotted to 3 treatments: 1) corn-based control d 0 through 85 (0%DDGS), 2) gradual step up to 60% DDGS diet (20% DDGS d 0 to 6, 40% DDGS d 7 to 13, 50% DDGS d 14 to 20, and 60% DDGS d 21 to 85; Step-up), or 3) 60% DDGS d 0 to 85 (60%DDGS). Overall, cattle fed 0%DDGS had increased (P < 0.05) DMI and ADG compared with those fed 60%DDGS or Step-up, and G:F was not affected (P = 0.42) by dietary treatment. On d 14, ruminal H2S concentrations were greater (P < 0.01) for cattle fed 60%DDGS and Step-up than for those fed 0%DDGS, and they did not differ (P >= 0.22) between DDGS-containing diets. These data illustrate that source of S impacts ruminal S metabolism and that S from DDGS is more readily reduced than S from Na2SO4 or H2SO4.