An implantable microsystem for electrical resistance and temperature measurements in cows with wireless capabilities suitable for reproductive management

In the cattle breeding industry, where artificial insemination techniques are employed, the successful detection of oestrus onset leads to considerable cost saving in herd management. One of the most reliable approaches is based on the determination of progesterone concentration in milk. However, these methods rely on the biosensor concept where a biological substrate is used in a chemical binding reaction to, directly or indirectly; produce some effect (electrical or light) that is used at the transducer level. These methods present several drawbacks concerning real-time measurements due to the complexity of the reactions involved and reagent/waste handling. Another approach is to combine measurements of electrical resistance of vaginal mucus and temperature to predict estrus. Using a low-power microsystem with wireless capabilities it is possible to take these measurements in-situ and more frequently. The proposed microsystem comprises a second-order delta-sigma modulator for analog to digital conversion and a class-E radio-frequency (RF) transmitter operating in the ISM-band of 433 MHz to transfer acquired data to a collar. Electrical resistance is measured by using a modified Wenner array and temperature by the on-chip temperature sensor. System (including battery and antenna) package is made of a tissue compatible material to allow implantation in the cow vulvar muscle