Application note for the use of a wireless device measuring reticular pH under practice conditions in a Swiss dairy herd

Subacute ruminal acidosis (SARA) is caused by ingestion of diets high in rapidly fermentable carbohydrates and/ or deficient in physically active fiber, often suspected to occur in high yielding dairy cows. Although SARA has been defined as repeatedly occurring periods of low ruminal pH, both practical measuring methods and threshold values remain subject to research.Precision livestock farming comprises use of real-time monitoring and managing systems for livestock farmers. Reticular pH can be monitored continuously on individual cow level by use of an indwelling bolus situated in the reticulum, linked to a wireless data transmission system. Practical experience in use of such boluses is scarce. The first aim of this field application was to test a commercially available bolus under field conditions in a dairy herd, and to assess the data obtained on herd level. The second aim was to suggest criteria indicative of SARA on herd level. The threshold for this investigation was set at pH <= 5.5 for >= 3 h, simultaneously occurring in >= 3 cows, by combining a testing strategy and a threshold from two peer-reviewed publications.Of 15 boluses administered, 12 (80%) provided reliable data. Reticular pH was measured in 10-min intervals. Useful data were obtained during the first 80 days after bolus application. This was considerably lower than the 150 days as described by the manufacturer.Based on pH measurements, a mean individual pH curve for each cow was created through grouping pH values for each time point over the entire period. The mean individual curve showed a circadian pH change with low pH values in the evening and variation of mean individual pH values among cows. No event of three cows simul-taneously showing a reticular pH <= 5.5 during a >= 3 h interval was recorded. Maximum time span during which pH was <= 5.5 in an individual cow was 4 h and 40 min.We conclude that use of the system on herd level is appropriate. Establishing a herd-level threshold for SARA based on continuous measuring systems requires integration of the mean individual pH curve, the individual minimal pH values, and the time span of low reticular pH.