Neubauer V, Humer E, Kröger I, Braid T, Wagner M, Zebeli Q
Institute of Animal Nutrition and Functional Plant Compounds, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Vienna, Austria.
Institute of Milk Hygiene, Milk Technology and Food Science, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Vienna, Austria.
J Anim Physiol Anim Nutr (Berl). 2018 Feb;102(1):343-349. doi: 10.1111/jpn.12675. Epub 2017 Jan 23.
Feeding of high-concentrate diets to cattle increases the risk of subacute ruminal acidosis (SARA). Indwelling wireless pH sensors have become popular as an early diagnostic tool for SARA recently. However, the recommended pH thresholds of SARA derive from measurements taken from free-rumen liquid (FRL) in the ventral rumen, and not from the reticulum, where the mentioned sensors are located. The aim of this study was to evaluate commercially available indwelling pH boli for the accuracy and precision in predicting ruminal pH of FRL and the particle-associated rumen liquid (PARL) under varying dietary concentrate levels. An additional aim was to define SARA pH thresholds of indwelled pH boli, which can be used for SARA diagnostics. The experiment was conducted with eight nonlactating rumen cannulated Holstein cows fed 0% or 65% concentrate. Data showed that the mean pH of indwelled boli was consistently higher than in FRL and PARL (pH 6.62 ± 0.02, 6.43 ± 0.02 and 6.18 ±0.02, respectively) across feeding regimens. Interestingly, the diurnal differences in pH among indwelled boli, FRL and PARL became greater during concentrate feeding, especially at 8 h after the morning feeding, suggesting that with high-concentrate diets a particular adjustment of reticular sensor pH vs. ruminal pH in FRL and PARL is needed. The concordance correlation coefficient analysis, representing the reproducibility of the bolus measurements, was high for bolus-FRL (0.733) and moderate for bolus-PARL (0.510) associations. Furthermore, the quantitative relationship of the pH in FRL and PARL to the pH of the boli was described by linear regression analysis. The study determined that the common SARA threshold of pH 5.8 in FRL corresponds to a bolus pH of 6.0.
给牛饲喂高浓度日粮会增加亚急性瘤胃酸中毒（SARA）的风险。植入式无线pH传感器作为SARA的早期诊断工具近来颇受欢迎。然而，SARA推荐的pH阈值来自瘤胃腹侧游离瘤胃液（FRL）的测量值，而非来自上述传感器所在的网胃。本研究的目的是评估市售植入式pH药丸在不同日粮精料水平下预测FRL和颗粒相关瘤胃液（PARL）瘤胃pH的准确性和精密度。另一个目的是确定植入式pH药丸的SARA pH阈值，可用于SARA诊断。实验选用8头安装瘤胃瘘管的非泌乳荷斯坦奶牛，分别饲喂0%或65%的精料。数据显示，在不同饲喂方案下，植入药丸的平均pH始终高于FRL和PARL（分别为pH 6.62±0.02、6.43±0.02和6.18±0.02）。有趣的是，在精料饲喂期间，尤其是在早晨饲喂后8小时，植入药丸、FRL和PARL之间的pH昼夜差异变得更大，这表明对于高浓度日粮，需要对网胃传感器pH与FRL和PARL中的瘤胃pH进行特殊调整。代表药丸测量再现性的一致性相关系数分析显示，药丸与FRL的相关性较高（0.733），药丸与PARL的相关性中等（0.510）。此外，通过线性回归分析描述了FRL和PARL中pH与药丸pH的定量关系。该研究确定，FRL中常见的SARA阈值pH 5.8对应于药丸pH 6.0。
