Oestrus detection in cows requires not only technical skill from the farmer but also a lot of labour investment. This points to the development of new devices aiming to improve oestrus detection.

Telemetric monitoring of temperature and activity in the cow was accomplished by the implantable capsule Capt alpha from ESAT-MICAS and IMAG-DLO. This capsule, 60 mm by 17 mm, transmits every second by RF three data bytes: an identification code of the animal and information from three sensors, a piezo-resistive accelerometer and two thermistors. The transmitter frequency is 30 MHz, FSK being used for data modulation. The expected battery duration time was 45 days. An RF receiver and a decoder were connected to a PC for continuous data recording.

A test capsule was implanted in an adult Frisian cow to follow inflammatory response, biocompatibility and in vivo electronics insulation from humidity. This capsule was inserted in the connective tissue lateral to the anus. A Capt alpha capsule was implanted in a Brown-Swiss cow, whose reproductive cycle was monitored during 45 days, with observation of the animal's behaviour in the exercise park and hormone level determination to test the feasibility of the new telemetric monitoring system as a helping tool to oestrus detection in the cow, without interfering with the stable routine. The animal's daily activity was video recorded. Heart rate monitoring was performed with the PCG capsule from University of Tras-os-Montes and Alto Douro (UTAD). PCG was implanted subcutaneously in the mitral area of the Frisian cow to detect S1. Heart rate in the Brown-Swiss cow was followed during 2-hour periods, placing the PCG capsule on the mitral area.

The test capsule was recovered 45 days after implantation showing no signs of damage or fluid invasion. The Capt alpha capsule, also removed 45 days after implantation, was in a similar condition. These results account for in vivo preservation of the battery and the circuitry.

Oestrus was confirmed by observation of excitement and mounting behaviour in the females in the exercise park and also by a fall in progesterone levels.

Data records show a different activity pattern during oestrus in the housed animal, with lower total activity, but with localised peaks of intense activity, never reached during control days. Temperature records show an increase of circa 0.5 oC when compared to a control day, reaching an increase of up to 1.0 oC in some night periods. Telemetric heart rate records during control and oestrus days were within the physiological range, heart rate being slightly lower during oestrus. However, the animal showed a higher rise in the heart rate, which took longer to stabilise, when the researchers approached during oestrus.

Results suggest that combining data from continuous temperature, activity and heart rate telemetric monitoring improves oestrus behaviour characterisation and detection.

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