Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE 68583-0908, USA.
J Anim Sci. 2013 Jul;91(7):3352-9. doi: 10.2527/jas.2012-5626. Epub 2013 May 8.
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 was analyzed for S. Steers fed INORG tended (P = 0.12) to consume 12% less DM. Total S intake was greater (P < 0.01) for steers fed WDGS (60 g/d) followed by ORG-H, and the lowest S intake was observed for CON (22 g/d). Intakes of ARPS and RAS were greater (P < 0.01) for steers fed WDGS followed by INORG, ORG-H, ORG-L, and CON diets. Steers fed WDGS and INORG diets spent 13% more time eating (P < 0.01) compared with other treatments. There was an interaction (P = 0.05) between treatment and time for ruminal [H2S]. Similar [H2S] were observed for steers fed INORG and WDGS diets (P = 0.28), which were greater (P ≤ 0.05) than other treatments. Greater ruminal [H2S] at 8 h compared with 13 h postfeeding was observed for steers fed ORG-H, ORG-L, and CON diets (P ≤ 0.04). Nearly 65% of ruminal [H2S] variation was explained (linear; P < 0.01) by RAS intake, ARPS explained 58% (linear; P < 0.01), S intake explained 29% (quadratic; P < 0.01), average ruminal pH explained 12% (linear; P < 0.01), and area below ruminal pH 5.6 explained 16% (linear, P < 0.01) of the variation. A 6% decrease in acetate (P = 0.01), 20% increase in propionate molar proportions (P = 0.02), and a lower acetate:proprionate ratio (P = 0.02) were observed for steers fed INORG compared with CON diet. The RAS concept is important for predicting ruminal [H2S] rather than just total S in the diet. Coefficients of RAS for individual ingredients can be predicted using in vitro procedures. Ruminal [H2S] may also modulate intake pattern.
研究了有机和无机硫源对采食量、采食量模式、瘤胃 pH、挥发性脂肪酸谱和瘤胃 H2S 浓度 ([H2S]) 的影响，这导致了一种测量瘤胃硫可用性以进行还原的方法的发展[瘤胃可用硫 (RAS)]，并与估计数量[调整瘤胃蛋白质硫 (ARPS)]进行了比较。5 头杂交肉牛（BW=548±46kg）被分配到 5×5 拉丁方设计中的 5 种日粮之一，并在 5 个 21 天周期内自由采食。牛只饲喂干压玉米日粮（CON）、无机硫源（硫酸铵；INORG）、有机硫源（玉米蛋白粉），日粮 DM 的 9.8%（ORG-L）或 23%（ORG-H），或湿酒精糟及其可溶性物（WDGS），占日粮 DM 的 50%。对于实验室程序，将来自饲喂 60%玉米日粮的小母牛的瘤胃液与 McDougall 缓冲液一起孵育。将瓶子在冰中冷却、离心和倾析，沉淀分析 S。饲喂 INORG 的牛只（P=0.12）倾向于减少 12%的 DM 采食量。WDGS（60g/d）和 ORG-H 组的总 S 摄入量较高（P<0.01），而 CON 组的 S 摄入量最低（22g/d）。WDGS 组和 INORG 组的 ARPS 和 RAS 摄入量较高（P<0.01），其次是 ORG-H、ORG-L 和 CON 日粮组。与其他处理组相比，饲喂 WDGS 和 INORG 日粮的牛只采食时间多 13%（P<0.01）。处理和时间之间存在交互作用（P=0.05），影响瘤胃[H2S]。饲喂 INORG 和 WDGS 日粮的牛只（P=0.28）的瘤胃[H2S]相似，高于其他处理组（P≤0.05）。与 13 小时相比，饲喂 ORG-H、ORG-L 和 CON 日粮的牛只在 8 小时时瘤胃[H2S]较高（P≤0.04）。瘤胃[H2S]的变化有近 65%（线性；P<0.01）可以用 RAS 摄入量来解释，ARPS 解释了 58%（线性；P<0.01），S 摄入量解释了 29%（二次；P<0.01），平均瘤胃 pH 解释了 12%（线性；P<0.01），瘤胃 pH 5.6 以下面积解释了 16%（线性，P<0.01）。与 CON 日粮相比，饲喂 INORG 的牛只的乙酸（P=0.01）减少 6%，丙酸摩尔比例增加 20%（P=0.02），乙酸：丙酸比例降低（P=0.02）。RAS 概念对于预测瘤胃[H2S]比预测日粮中的总 S 更重要。使用体外程序可以预测单个成分的 RAS 系数。瘤胃[H2S]也可能调节采食量模式。
