These results show that meloxicam orally administered to calves at the time of dehorning had effects on time spent at specific locations in the pen and lying activity during the seven days post-dehorning in this study. The cattle behavioral patterns illustrated an interaction between treatment and trial day, providing evidence that the meloxicam treatment was associated with changes in calf behavior, but these changes did not last the entire 7 days post-dehorning monitoring period. Faulkner and Weary (2000)  determined that administering a nonsteroidal anti-inflammatory drug to dairy calves while dehorning changes head shaking and ear flicking behaviors, but the effect of nonsteroidal anti-inflammatory meloxicam on pen activity has not been well described. Heinrich et al. (2010)  measured the behavior differences in calves post-dehorning receiving meloxicam using measurements of head shakes and ear flicks.
Sowell et al. (1999, 1998) [29, 30] concluded that morbid steers spent less time at the grain bunk compared to healthy steers in the feedlot. Their conclusions agree with the findings of this study that the MEL calves spent more time around the grain bunk on day 1 compared to the CON group (Figure 2). Calves that were administered MEL have shown to have a higher average daily gain ten days post-dehorning . Our study may offer an explanation for this finding as calves in the MEL group spent more time in the vicinity of the grain bunk. Todd et al. (2010)  administered MEL to calves with diarrhea and determined that MEL treated calves gained body weight faster and consumed more feed than the CON calves. This agrees with our results showing that MEL may alleviate pain associated with dehorning which could in turn cause an increase in appetite.
Doherty et al. (2007)  determined no statistical difference in the amount of time spent eating and drinking between calves administered lidocaine and the saline control groups post dehorning. This differs from our current findings and could be attributed to the different mode of action of the drug administered. Doherty et al. (2007)  administered 2% and 5% formulations of the anesthetic lidocaine. Research has demonstrated the effects of 2% lidocaine lasting 81.8 minutes in cattle . Coetzee et al. (2009)  determined that oral meloxicam has peak bioavailability at 11.6 hours and a half-life of 27.5 hours. The behavioral difference we observed related to grain bunk activity coincides with the time period when we expect the meloxicam to be most active (days 1 to 4). With meloxicam having longer lasting effects than lidocaine, this could affect behavior activity differently due to different analgesics administered. The difference between the Doherty et al. (2007)  study and our current study could also be partially attributed to the fact that they used visual observations and used 10 minute scan sampling with 144 observations per day for 3 days whereas we used 24 hour continuous surveillance for 7 days. On trial day 5, the MEL and CON groups both decreased the percent of time spent near the grain bunk to similar levels which may demonstrate the effects of meloxicam diminished.
In contrast to behavior at the grain bunk, the percent of times calves spent at the hay feeder was similar between treatment groups for all days except days 0 and 1 when calves in the CON group illustrated a marked increase in time at the hay feeder compared to MEL calves (Figure 1). The monitoring devices measure proximity to each feed area, not actual feed intake; therefore, the control calves may have been spending additional time at the hay feeder, but not actually eating. The wide diversity in the time spent at the water between the two groups provides some variability in the results and warrants further research. Although the percent time spent in the shed and other areas of the pen illustrated significant interactions between treatment group and trial day, there were no discernible patterns of behavioral change and no differences within trial days between treatment groups were identified.
The differences associated with the percent of time spent lying down between treatment group by trial day shows that meloxicam may be effective by increasing quiescence in calves (Figure 4). The meloxicam group spent a similar amount of time lying down throughout the trial whereas the CON group spent less time after dehorning and then reached similar levels to the MEL group on day 5. This lying activity would coincide of the effects of the analgesic wearing off on day 5. Mosher et al. (2010)  determined that calves that were administered meloxicam did not change lying behavior from pre to post-dehorning whereas within the placebo group lying activity decreased post-dehorning. Heinrich et al. (2010)  determined that calves administered MEL were less active for only 5 hours post-dehorning. This differs from our findings showing that calves administered MEL had increased lying activity for 5 days. This could be attributed to the fact that they had calves individually housed making activity monitoring difficult to perform and analyze and they administered lidocaine with intramuscular injection of meloxicam, whereas the calves in this trial were group housed and no local anesthetic was used.
Lying behavior can be associated with other painful events such as castration. González et al. (2009)  discovered that castration reduced time spent lying down. White et al. (2008)  determined that calves spent 82.2% time standing post-castration compared to only 37.9% pre-castration. This contradicts previous results where there were no significant differences in the percentage of time spent lying down between calves administered analgesic and the CON group . This differs from our current findings and again could be attributed to the mode of action of the analgesic, response to pain, or the method of behavior observation.
Lying behavior may be a good indicator of animal well-being. Lying behavior has also been associated with animal morbidity [18, 20]. An increase in amount of time standing could be related to pain. Hanzlicek et al. (2010)  determined that calves spent a greater proportion of time lying down after they were inoculated with Mannheimia haemolytica inflicting bovine respiratory disease. Hanzlicek et al. (2010)  also indicated that morbid animals spent more time lying down. This could be due to the depression associated with respiratory disease whereas dehorning is a more acutely stressful procedure. Treatment group was not associated with the percent time walking or the distance travelled. Research needs to be performed to determine the effect of analgesics on calves while dehorning to determine if behavior analysis is an adequate indicator for pain recognition. Further research also needs to be performed on the effect of meloxicam on different ages of calves.
Limitations of this trial include housing calves in a small pen environment and determining how behavior is related to pain and performance. Previous work has illustrated that calves displayed less activity and less sensitivity to pressure algometry following dehorning with meloxicam administration , and these findings support a link between measures of behavior and pain. Application of these results are limited to dehorning young calves, and it is important to note that all calves were dehorned in this trial. Some of the differences in behavior may be an effect of the meloxicam itself, but there have been studies performed with both dehorned and non-dehorned calves administered meloxicam that have shown effect of behavior changes beyond just the drug [28, 36]. The addition of a treatment group that was not dehorned, yet received meloxicam, could have helped delineate the potential behavioral effect of meloxicam without a pain event. Additionally, there are other common pain mitigation techniques (e.g. cornual nerve block) that were not tested in this experiment, and they should be evaluated in subsequent work. The triangulation system did not record location data at pre-defined intervals, but rather signals were triggered by movement resulting in varied intervals between location data points. The median interval of 7 seconds between location readings supports that location was monitored frequently; however, long periods of inactivity may result in a larger interval between data points. An objective of the trial was to compare location patterns between treatment groups and cattle in both groups were monitored using tags with the same reporting criteria.