New method to automatically evaluate the sexual activity of the ram based on accelerometer records

The ability of rams to serve as many ewes as possible is an important feature of their reproductive capacity. The ability to automatically evaluate serving capacity on farms might increase the interest of sheep owners in this important feature. The objective of the present study was to evaluate the suitability of a system to assess sexual activity of rams (number of mounts and services performed by rams) during field mating at pasture, in order to estimate the serving capacity of rams (defined as the number of services performed by one ram per unit of time). The system was composed by an inexpensive tri-axial accelerometer and a decision tree algorithm based on threshold values for data analysis. Eight rams carrying corresponding accelerometers (eight accelerometers were used simultaneously) were exposed to 163 ewes for 26 days. The sexual behaviour of rams (mounts and services) was observed during 2 h every morning during the 26 days, and the times at which these events occurred were recorded (416 h in total). Raw data were collected from accelerometers every 4 or 5 days and subsequently transformed and analysed by an algorithm developed for automatic evaluation. The records of three additional rams in a pen test and during 5 days of field mating were used for the training phase, while data of the eight rams recorded during the field mating period was used in the validation phase. The performance of this system depended on the ram. The overall sensitivity for mounting detection was 0.779 (minimum: 0.543; maximum: 0.909), while the total sensitivity for services detection was 0.940 (minimum: 0.792; maximum: 1.000). The efficacy for mounting detection (positive predictive value: PPV) was 0.929 (minimum: 0.679; maximum: 1.000), and the efficacy for services detection (PPV) was 0.929 (minimum: 0.850; maximum: 1.000). In conclusion, our results demonstrate that the serving capacity of rams can be automatically estimated by means of the system used in the present study; therefore, it might be a suitable tool for serving capacity evaluation during field mating in commercial flocks.