Impact of an inexperienced operator on photoplethysmogram for bovine heat detection

An essential part of efficient herd reproduction management is the prompt insemination of fertile cows after successfully noticing bovine heat. Signs of heat demonstrate that an animal is in estrus, ready to be inseminated. An affordable technique for heat detection is photoplethysmography (PPG, pulse oximetry), which can quantify changes in vulvar blood circulation (swelling and erythema). Previously, only experienced operators applied PPG devices. In this study, an inexperienced user clinically tested PPG for heat detection in nine cows. The analysis focused on the signal baseline (DC component), power, and kurtosis between 0.7 and 3 Hz. Compared to the experienced, inexperienced operator's PPG signal variability significantly increased. The green PPG signal baseline's range (a difference between the 25th and 75th percentile) almost tripled. Furthermore, variability in signal power increased between 6.9 and 13.1 times, indicating several operator-introduced oscillations. The results showed that inexperienced PPG operator retrieves more variable PPG signals than professionals, indicating a need for consistent device handling. The potential changes could include a pressure sensor or a clamp, guaranteeing constant pressure between the PPG sensor and the vaginal wall.