## 3 Results
\begin{table}
\begin{tabular}{l c c c c} \hline  & \multicolumn{2}{c}{**Trial 1**} & \multicolumn{2}{c}{**Trial 2**} \\ \cline{2-5}  & **Brand 1** & **Brand 2** & \(p\)**-Value** & **Brand 2** \\ \hline True birth alert (\%) & 0.30 \(\pm\) 0.15 & 0.56 \(\pm\) 0.17 & 0.26 & 0.00 \\ False birth alert (\%) & 0.30 \(\pm\) 0.15 & 0.44 \(\pm\) 0.17 & 0.51 & 0.50 \\ Missed birth alert (\%) & 0.40 \(\pm\) 0.16 & 0.00 \(\pm\) 0.00 & 0.01 & 0.50 \\ True birth event (\%) & 1.00 \(\pm\) 0.00 & 0.78 \(\pm\) 0.14 & 0.07 & 1.00 \\ Alert time lapse 1 (mins) & 341 \(\pm\) 173 & 290 \(\pm\) 153 & 0.829 & 235 \(\pm\) 285.63 \\ VIT retrieved & 2 & 5 & NA & 8 \\ Accuracy (\%) & 50 & 55 & NA & 0 \\ Specificity (\%) & 60 & 25 & NA & 0 \\ Sensitivity (\%) & 40 & 83 & NA & 0 \\ Precision (\%) & 50 & 62.5 & NA & 0 \\ \hline \end{tabular} \({}^{1}\) The time between VIT expulsion was recorded by the system, versus the time the research team received the VIT expulsion email for both true and false birth alerts.  
\end{table} 
Table 3: Comparison of the performance of two brands of birth alert systems based on vaginal implant tags fitted to pregnant beef cows in extensive production systems (Trial 1 and 2). between the daily average X- and Y-axis counts in Trial 1 was 0.66 (\(p<0.001\)) and 0.80 in Trial 2 (data not shown; \(p<0.001\)). The Pearson correlation coefficient between distance travelled and the average X- and Y-axis in Trial 1 was 0.51 and 0.58 (\(p<0.001\)), and 0.51 and 0.77 in Trial 2 (\(p<0.001\)), respectively. Approximately 17,000 vaginal temperature datapoints were collected from five Brand 2 cows in Trial 1 and approx. 160,000 vaginal temperature datapoints from eight Brand 2 cows in Trial 2. Vaginal temperature data for three Brand 2 VIT devices retrieved in Trial 1 are shown in Figure 4 with cow 1 and 2 calving after sunset and the VIT experiencing a sharp reduction in temperature, which triggered the birth alert. However, cow 3 expelled the VIT at nontime, showing a sharp decrease followed by a sharp increase in temperature and the birth alert was not triggered. There were clear temperature patterns within and between days in all animals, with a large variability of over 3 \({}^{\circ}\)C during the day. Diurnal patterns were evident with temperature increasing during the morning and decreasing during the night to reach the lowest values at the end of the night (Figure 5). Figure 2: Average distance travelled per day by collared cows 30 days each side of the calving date in Trial 1 (**a**) and 2 (**b**). Means with an Asterix (*) indicate a significant difference from the day of calving (\(p<0.05\)). Means with two Asterix (**) indicate a significant difference from day 1 (\(p<0.05\)). Only collared cows with a confirmed calving date (\(n=8\) in Trial 1 and \(n=7\) in Trial 2) were included. Figure 4: Vaginal implant tag temperature of three cows in the lead up to calving. Arrows indicate the VIT expulsion time. Figure 3: Average activity counts of the accelerometer X- and Y-axis for collared cows 30 days each side of the calving date for Trial 1 (**a**) and Trial 2 (**b**). Means with an Asterix (*) indicate a significant difference from the day of calving (\(p<0.05\)). Means with two Asterix (**) indicate a significant difference from day 1 (\(p<0.05\)). Only collared cows with a confirmed calving date (\(n=8\) in Trial 1 and \(n=7\) in Trial 2) were included. Average activity data from VIT in Trial 2 show the activity patterns for eight cows over the trial period (Figure 6). The activity level dropped to zero after the early expulsion of the VIT for two cows, while the other VIT ran out of battery before expulsion occurred, so drops in activity were not captured (Figure 6). There was a higher density of geolocation fixes near the water and supplementation points (data not shown), however most cows solved in less frequented areas of the paddock.