Department of Animal Science, Texas A&M University, College Station, TX 77843, USA.
Texas A&M AgriLife Extension, Texas A&M University, College Station, TX 77843, USA.
J Anim Sci. 2021 Oct 1;99(10). doi: 10.1093/jas/skab260.
Rumen acidosis is a common metabolic disorder occurring when organic acid production exceeds clearance capacity, reducing ruminal pH. The occurrence of acidosis has been directly correlated to the ratio of concentrate to forage in the diet. However, rates of substrate fermentation and acid absorption vary at different locations in the reticulo-rumen. The objective of this study was to determine the pH and redox potential (Eh) in different locations of the reticulo-rumen using 16 ruminally cannulated steers (309 ± 43 kg) receiving different supplementation levels of quebracho extract (QT; Schinopsis balansae) within a grower type diet (CP: 13.4%; total digestible nutrients [TDN]: 70.4%; and ME: 2.55 Mcal/kg, dry matter [DM] basis). Animals were randomly assigned to one of four dietary treatments: QT at 0%, 1%, 2%, and 3% of DM (QT0, QT1, QT2, and QT3, respectively), containing about 0%, 0.7%, 1.4%, and 2.1% of condensed tannins (CT), DM basis, respectively. Animals were adapted to the basal diet for 12 d before being introduced to predetermined treatments for 4 weeks (wk), with diets provided twice daily to allow ad libitum intake. Weekly measurements of ruminal fluid pH and Eh were taken 4 h post-feeding using a portable pH meter with two probes (pH and redox) in four locations of the reticulo-rumen (reticulum, cranial sac, dorsal sac, and ventral sac). Data were analyzed using a random coefficients model with the pen as a random effect and wk as repeated measures, with DM intake included as a covariate. There was no interaction among treatments, location, and wk (P ≥ 0.882) on reticulo-ruminal pH. Overall, ruminal pH was lower for QT0 and QT1 compared to QT3 (P < 0.001). The pH in the reticulum was greater than those of the ventral and dorsal sacs (6.05 vs. 5.94, 5.89, respectively; P ≤ 0.001) but similar to cranial sac (6.00). Reticular pH was positively correlated with the ruminal locations (≥0.78; P < 0.001). The linear equation to estimate ruminal mean pH using reticulum pH had an intercept and slope different from zero (P ≤ 0.04), but CT (% DM) was not different from zero (P = 0.15), root mean square error of 0.15, and R2 of 0.778: 0.723 (±0.36) + 0.857 (±0.059) × reticulum pH + 0.033 (±0.023) × CT. The Eh was lower for QT0 in week 1 than all other treatments (P < 0.001). We concluded that reticulo-ruminal pH differs among locations in the rumen regardless of QT supplementation level and days on feed, with reticular pH being the highest.
瘤胃酸中毒是一种常见的代谢紊乱，当有机酸的产生超过清除能力时就会发生，从而降低瘤胃 pH 值。酸中毒的发生与日粮中精料与粗料的比例直接相关。然而，在反刍囊中不同部位，基质发酵和酸吸收的速率存在差异。本研究的目的是使用 16 头瘤胃内置有瘘管的育肥牛（309 ± 43 kg），在生长育肥型日粮（CP：13.4%；总可消化养分[TDN]：70.4%；代谢能[ME]：2.55 Mcal/kg，干物质[DM]基础）中添加不同水平的奎那酸提取物（QT； Schinopsis balansae），确定反刍囊中不同部位的 pH 值和氧化还原电位（Eh）。动物随机分配到四个日粮处理组之一：QT 为 0%、1%、2%和 3%DM（QT0、QT1、QT2 和 QT3，分别），分别含有约 0%、0.7%、1.4%和 2.1%的单宁（CT），DM 基础。动物适应基础日粮 12 天后，再用 4 周（wk）的时间引入预定的处理方案，每天喂两次以允许自由采食。在饲喂后 4 小时，使用带有两个探头（pH 和 Eh）的便携式 pH 计在反刍囊的四个部位（网胃、前囊、背囊和腹囊）测量瘤胃液 pH 值和 Eh 值。数据采用随机系数模型进行分析，以栏为随机效应，wk 为重复测量，DM 摄入量为协变量。在反刍囊 pH 值方面，处理、位置和 wk 之间没有相互作用（P ≥ 0.882）。总体而言，QT0 和 QT1 的瘤胃 pH 值低于 QT3（P < 0.001）。网胃的 pH 值高于腹囊和背囊（6.05 与 5.94、5.89，分别；P ≤ 0.001），但与前囊相似（6.00）。网胃 pH 值与瘤胃位置呈正相关（≥0.78；P < 0.001）。使用网胃 pH 值估算瘤胃平均 pH 值的线性方程截距和斜率不为零（P ≤ 0.04），但 CT（%DM）不为零（P = 0.15），均方根误差为 0.15，R2 为 0.778：0.723（±0.36）+0.857（±0.059）×网胃 pH 值+0.033（±0.023）×CT。QT0 在第 1 周的 Eh 值低于其他所有处理组（P < 0.001）。我们得出结论，无论 QT 补充水平和采食天数如何，反刍囊中不同部位的 pH 值都存在差异，网胃中的 pH 值最高。
