The eBolus

Designed for Research

Please note that the boluses in our Farmpack and Vetpack are the same variation of eBolus, it is the additional support offered with each package that differs.

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

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 then can be retrieved every time the mobile phone handset is brought within range of the cow.

eBolus Features

  • It is the smallest bolus size available today.
  • It has the longest life expectancy at 5 months of data collection.
  • It can be inserted at any point in the daily feeding regime with a bolus gun.
  • One end is weighted to encourage the bolus to sink with the sensor downwards into the reticulum.
  • It collects reliable, stable data – eCow uses the best quality sensors available.
  • The metal cap protects the pH sensor from rocks and hardware swallowed by the cow.
  • It has a smooth surface as to not cause distress or hard to the animal – No protruding edges.
  • Instant data analysis.
  • Data is sent directly to any nominated database.


  • Bolus Length: 135mm
  • Bolus Diameter: 27mm
  • Weight: 150g
  • Specific Gravity: 2.7
  • Temperature Accuracy: +/- 0.1°C
  • pH Accuracy: +/- 0.1pH
  • Data samples every minute to provide 96 data points per day.
  • Data Storage: 2700 lines (4 weeks at 15 minute samples).
  • Up to 5 months of logging
  • Frequency: 432MHz
Typically boluses are sold in multiples of 6 utilising eCow’s innovative packaging method that provides protection for boluses through transit and storage.

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.