3.1.5. Horses

All the horses accepted the equipment without any reaction. Occasionally it was pushed posteriorly if a horse rubbed on a wall or fence, but repositioning was rarely required. Responses at TT on the leg were a clear leg lift or stamp, or occasionally the horse would nose or even bite at the site. Responses

to the thoracic site were more di fficult to detect as a skin flick could be obscured by the more bulky testing equipment used in large animals and the horses appeared less responsive at this site. However, a skin flick, a bend of the body away from the testing site or turning to look at the site were also commonly seen. Skin temperature was lower on the leg than the thorax and was more dependent on ambient temperature. The TT was higher on the thorax than on the leg. Group HBR skin temperatures were 36.7 ± 0.4 (thorax) and 32.7 ± 1.0 (leg), and TT 54.8 ± 1.8 (thorax) and 46.9 ± 3.2 ◦C (leg). Group HPEN skin temperatures were 36.7 ± 0.4 (thorax) and 32.7 ± 1.0 (leg), and TT 54.8 ± 1.8 (thorax) and 46.9 ± 3.2 ◦C (leg). Leg skin temperature and TT were significantly lower than on the thorax (*p* < 0.001). Skin temperature and TT ranges in the smaller groups (HWS, HNO, HWS) are shown in Table 1. The TT in horses given analgesic treatment (groups HBR, HNSW, HNO, HWS and HPEN) increased above baseline between 10 min and 1–2 h. It reached cut-out (55 or 60 ◦C) in all except HPEN horses where the highest TT was 53 ◦C. All TTs had returned to baseline three hours after dosing and were within the same range the following day (see Figure 9a,b).

**Figure 9.** (**a**) Mean ± SD baseline (no treatment) thermal nociceptive thresholds (TTs) (◦C) measured on the thorax in cats (*n* = 16), dogs (*n* = 8) and horses (*n* = 21) and on a leg in horses (*n* = 15), sheep (*n* = 11) and camels (*n* = 3). (**b**) Mean ± SD pre treatment and peak post analgesic treatment (see text for detail) TTs (◦C) measured on the thorax in cats (*n* = 6), dogs (*n* = 2) and horses (*n* = 8) and on a forelimb in horses (*n* = 10). Thermal threshold reached cut-out (55◦ or 60 ◦C as shown) in all cats, dogs and in horses using the leg site. For the horse thoracic site, those reaching cut-out (*n* = 4) were deemed a TT of 60 ◦C for illustrative purposes.
