An Easier Way to Temp Calves?

Detecting subtle changes calves’ body temperature has been shown to provide valuable insight into their health status and allow for proactive interventions to address disease challenges early in their progression.

But in most commercial settings, it is not practical to conduct daily rectal temping of every calf. In recent years, researchers have turned to artificial intelligence to study more-automated ways to routinely gather individual-calf body temperatures.

In a recent study published in the Journal of Dairy Science, a group of researchers from the University of Guelph compared the accuracy of manual, rectal temping, with that of an infrared thermography (IRT) camera. The team, led by David Renaud, theorized that if IRT readings could be validated as consistent with rectal temps, this quick, non-invasive method could be used routinely to reliably detect calf body temperature changes.

The study was conducted at a commercial calf facility in southwestern Ontario, Canada. A total of 318 male Holstein calves were enrolled between May and August 2019.

At 8:00 a.m. daily, each calf’s body temperature was evaluated for 14 consecutive days via both rectal thermometer and an IRT camera (FLIR One Pro) installed on a cell phone. The IRT camera measured temperature using an ocular (eye) scan.

The researchers designed the study to mimic regular calf production versus a laboratory setting. They also evaluated a large number of commercial calves,  to ensure the results would be transferrable to everyday management systems. Although the IRT camera they chose had a slightly lower accuracy rate (95%) than other options, they selected it because it was cell-phone compatible and “would be a practical application for use by producers or veterinarians,” they said.

While a few readings had to be removed from the data due to accuracy issues, 4,427 – or 99.6% of the data points – were included in the final evaluation. During the study period, a livestock heat stress monitor also was used in the calf barn to record air temperature and humidity readings every 15 minutes.

Ultimately, the researchers determined that the IRT method evaluated was not accurate enough to be used instead of rectal temperature. “The goal of this IRT system was to evaluate its use as a potential point-of-care evaluation tool to serve as a proxy for rectal temperature in calves to save time and labor,” they wrote. “Thus, it is imperative that IRT readings are precise, accurate, and without bias, especially to justify replacement of the reference standard.”

The data indicated that the IRT system deviated from the rectal readings by a mean average of nearly one full degree F (0.55°C). Only 78% of the IRT readings correctly determined whether or not an animal had a fever.

The research team determined that the accuracy differential was likely due to ambient environmental conditions – namely, air temperature – which skewed the readings of the IRT method.

IRT technology has been evaluated in other studies that showed it could accurately predict ensuing calf health issues. But given the equipment and conditions evaluated in this study, the researchers determined it could not be used in a commercial setting to reliably replace the “gold standard” of rectal temperature to evaluate calf body temperature.

For more on calf health, read:  

• Do you have a Calf Herd Program?
• Researchers Explore Risks of Feeding Waste Milk
• “Must-haves” for Autofeeder Barns