Researchers at the University of California-Davis and the University of British Columbia are evaluating the effect of cooling gel on pain sensitivity and healing of hot-iron cattle brands.In presenting their results here at JAM 2013, they noted that hot-iron branding is painful for cattle, but little is known about the duration of or effective methods to control this pain. Previous work with pigs indicated that cooling burns with a gel (active ingredient, tea tree oil) improved healing compared with untreated wounds.
For the study, steers (210 ± 5 kg) were hot-iron branded and allocated to one of three treatments: control (n = 24), 1 gel application immediately after branding (1×; n = 12) or 2 gel applications, once immediately after branding and 24 hours later (2×; n = 12). Wound sensitivity was assessed by applying, in five locations (in the center, at the top of, 5 and 10 cm above the brand and on the non-branded side), a known and increasing force with a von Frey anesthesiometer until the animal showed a behavioral response. Healing was measured with a 6-point scale (1 = fresh brand, 6 = no scabbing and fully re-pigmented). Both measures, along with weight gain and temperature of the wound were recorded before, 24, 48, 72 hours and 1, 2, 3, 4, 5, 8 and 10 weeks after branding and analyzed with a mixed model.
The researchers reported that the gel immediately cooled the brand (38.7 ± 0.7 vs. 34.9 ± 0.6°C for the control vs. 1×/2× treatments), but there were no treatment differences in wound temperature at any other time (P > 0.26). All wounds were at least partially re-pigmented by 10 weeks, but only 46% of brands were fully healed at this time.
The healing process was slowed in the 2× group (e.g., at 21 day 2.6 ± 0.1 vs. 2.0 ± 0.2, for control/1× vs. 2×, respectively, P < 0.01). Brands remained sensitive throughout 10 week (before vs. all other time points, in center of brand, P = 0.01). Overall, wound sensitivity tended to be lower for the 1× treatment in the center, 5 and 10 cm from the brand (177 ± 31, 318 ± 68, 412 ± 60 vs. 205 ± 29, 355 ± 67, 460 ± 59 g force for the 1× vs. control treatments, P ≤ 0.07).
Weight gain was reduced in the week of branding, but was not affected by gel application.
In conclusion, the researchers said applying gel 1× tended to reduce wound sensitivity. However, 10 weeks after the procedure, hot-iron brands remained more sensitive than non-branded tissue and 54% were not fully healed. These results, they said, contribute to animal welfare concerns about hot-iron branding.