Abstract
The productivity of dairy cows has increased dramatically over the last decades. A consequence of developing dairy productivity is associated to the adequate advanced feeding strategies. However, with failures in feeding policies, such as increased concentrate diets, the incidence of subacute rumen acidosis （SARA） has become a critical issue for the dairy industry, and clinical veterinary medicine. If SARA occurs in a cow herd, clinical disorders such as diminished appetite, low milk fat syndrome, abomasum displacement and ulcers, and rumenitis will increase, and the amount of lactation and reproduction performance will decrease, which lead to serious economic loss. To diagnose SARA, accurate monitoring of ruminal pH is needed. In recent years, a cable pH measurement system has been developed, enable research into the morbidity of SARA by continuous measurement of ruminal pH. However, the use of this measurement system in fi eld cases is difficult due to the need of surgically install the rumen-fistula. From such a background, Sato et al. developed recently a radio transmission pH sensor, which can be administered orally into the rumen to monitor SARA. In this study, we assess the diagnosis and control of SARA using a radio transmission pH sensor in dairy cows. In a primary experiment, ruminal fluids samples was collected from the rumen-fistulated cows. The pH values of collected samples were compared to the pH values of the automated pH sensor. The both pH values were positively correlated significantly. In the second experiment, we investigated the accuracy of the sensor as well as changes in the ruminal pH of cows fed different diets, and compared the ruminal （bottom and middle） and reticular pH. The ruminal pH of cows fed the high-concentrate diet tended to drop more than that of cows fed a roughage diet. In addition, although a significant positive correlation was observed between reticular pH and ruminal pH, the latter remained slightly low compared to the former. Furthermore, the relationship between ruminal pH and ruminal temperature was investigated. When fed the RAI diet, ruminal pH dropped significantly, and ruminal temperature tended to rise significantly. A significant negative correlation was observed between ruminal temperature and ruminal pH. In conclusion, it is revealed the accuracy of the radio transmission pH sensor and diagnostic criteria of SARA via continuous measurements of the ruminal pH in SARA cows. Under SARA condition, the ruminal pH was less than 5.6, the reticular pH was less than 6.3 for more than 3 h per day. The radio transmission pH sensor may be effective to diagnose of SARA in the dairy cows. The results of this study could be applied to control of the advanced feeding strategies and prevention of SARA in dairy cows.
