Field-trial evaluation of an automatic temperature measurement device placed in the reticulo-rumen of pre-weaned male calves

• Automatic measurements of the reticulo-ruminal temperatures are feasible in pre-weaned calves.
• An early detection of increased rectal temperature is possible, but warrants further research.
• The implementation of an alarm system helps to improve the early detection of increased rectal temperature.

The assessment of the rectal temperature plays an important role in the early detection of bovine respiratory disease (BRD) in young calves, but the measurement is invasive and labor-intensive. The aims of this retrospective field-trial evaluation were to assess the correlation between the automatic measurements of the reticulo-ruminal (ReRu) temperature and the rectal temperature and to evaluate the diagnostic accuracy of a cumulative sum (CUSUM) control chart to detect pre-weaned calves suffering from BRD. In 150 male fattening calves (16.6±3.3 d at arrival) the ReRu-temperature was obtained every 5 min automatically with a wireless device over a period of 8 weeks. Data was averaged over periods of 30 min and 4–6 h (day periods). The 30-min means were further evaluated using CUSUM control charts. All calves were inspected by trained persons at least twice a day and rectal temperatures were measured in calves showing visible signs related to BRD. A ReRu hyperthermia (ReRu temperature ≥40 °C) was detected in 139 calves over 30 min and in 99 calves over day periods, respectively. During the evaluation period 30 animals were affected by BRD (rectal temperatures ≥40 °C and one additional clinical sign). The correlations between rectal temperatures and both the corresponding 30 min as well as the day period ReRu temperatures was r=0.75. The sensitivity (Se) and specificity (Sp) of ReRu hyperthermia for the 30 min means to detect BRD were 77% and 97%, respectively, whereas means of the day periods had a Se of 61% and a Sp of 97%. The CUSUM test revealed a Se of 71% and Sp of 98% to detect BRD. On average, by the CUSUM method calves with clinical signs of BRD were identified 3.5 d earlier. In conclusion, the automated ReRu temperature measurement possesses potential for the early detection of febrile responses in very young calves warranting further investigations.