Evaluating velvet antler growth in red deer stags (Cervus elaphus) using hand-held and digital infrared thermography

Bowers, S., Gandy, S., Dickerson, T., Brown, C., Strauch, T., Neuendorff, D., Randel, R. and Willard, S. 2010. Evaluating velvet antler growth in red deer stags (Cervus elaphus) using hand-held and digital infrared thermography. Can. J. Anim. Sci. 90: 13-21. The objectives of this study were to evaluate whether velvet antler (VA) surface temperature gradients, as measured by either a single-spot infrared temperature (SST) sensor (SSTS; exp. 1) or digital infrared temperature (DIT) imaging (DITI; exp. 2), would pattern VA growth. In exp. I, growth rates and SST were obtained from yearling (n = 8) and mature (n = 17) red deer stags (Cervus elaphus) every 14 d following eruption through day 56 in yearlings and day 112 in mature stags. In exp. 2, growth rates and DIT (main beam VA base, mid and tip temperatures) were obtained from red deer stags (n = 31) every 14 d following eruption through day 126. Background temperatures were recorded in conjunction with thermal antler measurements. In exp. 1, yearling VA base and tip SST were positively correlated with one another (P<0.01); however, both measurements were also positively correlated with background SST (P<0.05). In mature stags, VA base SST paralleled (P<0.05) background SST measures, while tip SST did not change from day 56 through day 112. In exp. 2, VA DIT changed (P<0.01) over time and differed (P<0.01) between base, mid and tip. During the early growth period. VA temperatures increased (P<0.05) from 38.9 +/- 0.2 degrees C at the base to 39.3 +/- 0.2 degrees C at the tip of the antler. In contrast, during the late growth period. DIT was higher (P<0.01) at the base (36.8 +/- 0.3 degrees C) than at the tip (35.7 +/- 0.3 degrees C) of the antler. In conclusion, SSTS did not have the sensitivity to signify changes in antler growth rates. However, in exp. 2 using DITI, VA thermogenesis paralleled VA growth suggesting that DITI may have value in monitoring VA growth.