The eBolus

Designed for Research

 We are updating the design of the bolus to give longer radio range and continuously available data through the farm network.

The eBolus is a wireless telemetric device swallowed by the cow that provides continuous and accurate measurements of pH, temperature and reduction potential inside the reticulum. It records data at 1 minute intervals and saves averages every 15 minutes to provide 96 readings per day. This data is stored on the bolus and is continually transferred to a base station from which it can be downloaded.   As long as the animal stays within range of the base station (about 200m) there will be a continuous record of rumen pH throughout an experimental period.  

The development is still a work in progress and we anticipate supplying this product from October 2020 (subject to government restrictions regarding the Covid-10 pandemic which may affect our build and test program.) 

We call this bolus the Mk3 replacing the Mk2 product with its resin moulded construction.


Mk3 eBolus Features



  • Greater radio range

  • Portable fixed base stations continually downloading data

  • reduced size of bolus

  • data accessible to office desks via the local area network.

  • Potential multi-sensor

The Mk3 is a product in development but with our fifteen years experience of designing and making pH telemetry boluses for research scientists around the world we are fairly confident in our ability to meet a demanding specification for research scientists.


  • Accuracy pH +/- 0.1 for every 30 days in the rumen

  • Data averaged every 15 minutes

  • bolus diameter 23 mm length <100mm

  • bolus specific gravity 2 (locates to rumen-reticulum)

  • Radio range 200-500m

  • each bolus identified seprately

  • multiple boluses possible

  • no interference from magnets

  • operational lifetime 90-150 days (target)


pH Measurements


The main feature of the eBolus is its ability to accurately and continuously monitor rumen pH. The pH of a solution is a measure of the acidity of a solution, and as the acidity increases the pH drops. More specifically it is a measure of the relative hydrogen ion concentration and, as the hydrogen ion is electrically charged, it is possible to measure pH electrically.

When in constant use (i.e. within a cows rumen) the sensor readings can remain stable for up to 150 days (5 months), far longer than similar products.

The graph below shows the pH variation over a 3 month period, with the red line showing the threshold for acidosis. Towards the beginning of this period the cow shows signs of being at risk of acidosis. This is easily recognisable and afterwards the pH quickly rises to a safe level.

Temperature Measurements


As well as the pH functionality, the eBolus continuously logs the temperature of its environment. This information can be used to monitor drinking activity, as cold water entering the rumen correlates with a sharp but brief drop in the temperature reading. It is important to note that these events are not changes in the overall body temperature of the cow and should not be treated as such. However, changes in the average (mean) daily temperature of the cow’s rumen can be linked to an overall change in the body temperature of the cow. As it is consistently 1°C above the rest of the body, the temperature of the rumen can be relied upon to give an accurate indication of overall body temperature. Peaks in temperature are often observed when a cow is suffering from an infection such as mastitis. Infections such as this may also be observed as a lack of drinks taken and a drop in ruminal pH.

Boluses affected by drift

Our system is very accurate allowing you to detect SARA and other conditions very easily, but also means you can observe when drift starts.

The below graph shows data from a trial by one of our research customers. In the final period a narrowing of the pH range followed by a steep incline towards pH 7 can be observed. This is pH sensor drift caused by rumen fluid diffusing into the sensor and poisoning the reference electrode. We would advise that 150 days is the maximum length of time to trust the data when the bolus has not been retrieved and recalibrated (only possible in fistulated/cannulated cattle). For more information on drift in eCow boluses please see this news post.

Some companies include algorithms that attempt to compensate for this drift, but until the drift is rigorously characterised these algorithms will only serve to further complicate the data received. What you get from the eCow bolus is the raw data without any “drift compensation”. As drift is non-linear it is impossible to write compensating software, it is best to analyse this by eye and exclude compromised data.


To view our GLP (Good Laboratory Compliance) Form, Click Here.