93 The efficiency of estrus detection by accelerometry in Holstein and Japanese Black crossbred cows

Accurate oestrus detection is important in order to perform AI and embryo transfer procedures at appropriate times. Pedometers and accelerometers have been utilised in the livestock industry to detect oestrus. However, the efficacy of these devices in beef cattle production systems remains unclear. In this preliminary study, we evaluated the efficacy of a commercially available accelerometer device for oestrus detection in nonlactating Holstein×Japanese Black crossbred cows (n=14). Accelerometer devices (Farmnote Color, Farmnote Inc., Hokkaido, Japan) were placed on the neck of each animal and remained in place for 3 months. Cows were kept in a pen during the day (8-9 cows/pen) and a pasture during the night. Cows were visually monitored for oestrus activity twice daily in the morning and evening for 30min. The activity of cows detected by the sensor was recorded every hour. Oestrus occurrence and duration were automatically detected and calculated by the device. Alerts generated by the device were categorized as either true positives (TP), false positives (FP) or false negatives (FN). True positives were defined as the observation of oestrus in conjunction with a device-generated oestrus alert or confirmation of the presence of a corpus luteum (CL) by ovarian ultrasonography 5 days following an oestrus alert. False positives were defined as events in which an oestrus alert was generated by the device, but no corresponding visual observation of oestrus occurred or a CL was not present 5 days following the alert. False negatives were cases where oestrus was observed visually but there was no corresponding device-generated oestrus alert. Reasons for FP were categorized into 1 of 3 categories defined as (1) other cows in oestrus in the same pen, (2) cows that were moved from other herds, (3) ovarian disorder such as follicular cyst, and (4) unknown. Statistical analyses were conducted using Student’s t-test. Results were considered significant at P<0.05. A total of 58 alerts were generated by the accelerometer devices. The percentage of TP and FP were 46.6 and 53.4%, respectively. Of the FP, 46.7% (14/31) were generated due to other cows in the same pen being in oestrus. During the study, there were 33 visually observed estruses for which there was also a corresponding device alert. Of these, 81.8% were TP and 18.2% were FN. Oestrus duration was significantly longer for TP than for FP (15.5±5.2v. 11.5±3.8 h; P<0.01). In addition, the change in activity at 2-9h after device-generated alerts was greater for TP than for FP (P<0.05). Oestrus duration (15.5h) for TP in the present study was similar to that observed previously by pedometer (16.8h) or temperature measurement (16.3h) in beef cattle (Sakatani et al. 2016 J. Reprod. Dev. 62, 201-207, DOI: 10.1262/jrd.2015-095). These results indicate that accelerometry could be effective for detecting oestrus in beef cattle. However, FP rate was quite high. The FP rate could be decreased by improving the alert detection threshold because the duration and change in activity were lower in FP cows. Further research with a greater number of animals is necessary to confirm these preliminary observations. This study was supported by the Project of the NARO Bio-oriented Technology Research Advancement Institution (AI-Project, The Special Scheme to Create Dynamism in Agriculture, Forestry and Fisheries through Deploying Highly Advanced Technology).