The intervals to ovulation of both AAM found in this study are similar to Valenza et al. (2012; 28.7 h), using a similar neck-mounted AAM, as well as other studies using pedometers (29.3 h; Roelofs et al., 2005a; Roelofs et al., 2006), pressure-sensing systems (27.6 h; Walker et al., 1996), and visual detection (30.6 h; Roelofs et al., 2005b). Stevenson et al. (2014) also reported similar intervals to ovulation using a pressure-sensing system (26.4 h) and a collar-mounted AAM (25.7 h). Suthar et al. (2011), on the other hand, reported a shorter interval to ovulation (20.6 h) using visual observation on tiestall-housed cows.