Pain and anxiety are two of the most important concerns in clinical veterinary medicine because they arise as consequences of multiple factors that can severely affect animal welfare. The aim of the present review was to provide a description and interpretation of the physiological and behavioral alterations associated with pain and anxiety in equines. To this end, we conducted an extensive review of diverse sources on the topic. The article begins by describing the neurophysiological pathway of pain, followed by a discussion of the importance of the limbic system in responses to pain and anxiety, since prolonged exposure to situations that cause stress and pain generates such physiological changes as tachycardia, tachypnea, hypertension, hyperthermia, and heart rate variability (HRV), often accompanied by altered emotional states, deficient rest, and even aggressiveness. In the long term, animals may show deficiencies in their ability to deal with changes in the environment due to alterations in the functioning of their immune, nervous, and endocrinologic systems. In conclusion, pain and anxiety directly impact the homeostasis of organisms, so it is necessary to conduct objective evaluations of both sensations using behavioral scales, like the horse grimace scale, complemented by assessments of blood biomarkers to analyze their correlation with physiological parameters: Heart rate, respiratory rate, HRV, the parasympathetic tone activity index, lactate and glucose levels, and temperature. Additional tools – infrared thermography, for example – can also be used in these efforts to improve the quality of life and welfare of horses.

No studies have induced maternal behavior in goats through hormonal treatment. We evaluated whether ovariectomized goats treated with estradiol benzoate (EB2; n = 7 nulliparous and 10 multiparous goats) or progesterone + estradiol benzoate (P4 + EB2; n = 7 nulliparous and 7 multiparous goats), before or after vagino-cervical stimulation (VCS), displayed maternal behavior. When all goats were measured within treatments, in the EB2 group, low-pitch bleats were more frequent, and the time spent cleaning the kids was longer after VCS (p < 0.01), while location changes were more frequent before VCS. In nulliparous goats, those in the EB2 group emitted more low-pitch bleats after VCS than before (p = 0.04). The frequency of location changes was higher before VCS than after (p = 0.05). In multiparous goats, the frequency of smelling the kids and aggression toward the kids before VCS was higher in the EB2 group than in the P4 + EB2 group (p < 0.01). Within treatments, the EB2 group emitted more low-pitch bleats after VCS than before (p = 0.01), and the duration of cleaning the kids was longer after VCS than before (p = 0.028). Within the P4 + EB2 group, the kids were smelled more frequently after VCS than before (p = 0.03). The maternal index after vagino-cervical stimulation was higher in goats with EB2 (p = 0.002). Nulliparous goats treated with P4 + EB2 had a higher maternal index compared with those treated with EB2 alone (p = 0.04). In conclusion, regardless of parity, maternal behavior induced with the EB2 treatment was better when VCS was applied. Likewise, maternal experience altered the response. In multiparous females, any of the treatments were better after VCS, while in nulliparous females, this was only evident with the EB2 treatment.

Parasympathetic tone activity (PTA) and its association with behavior in conscious versus anesthesia in horses are unknown. To study PTA, heart rate (HR), minimum alveolar concentration (MAC), and mean arterial pressure (MAP) during castration under anesthesia. To study PTA, HR, Horse Grimace Scale (HGS), locomotor activity (LA), and behavior in conscious horses before and after castration. Pilot study including seven healthy adult horses. After habituation (days 1, 2, and 3), PTAm, HR, HGS, LA, and behavior were investigated during pre-surgery (days 4-, 5-, and one-hour pre-anesthesia), and post-surgery (6 h post-surgery and days 7 and 8) periods. PTAm, HR, MAP, and MAC were recorded during castration. PTAm increased significantly during anesthesia (P < 0.001), with sequential increase as time passed (P < 0.001): 15 min = 27.4% (62.6, CI 57.3-67.8), 20 min = 38.2% (70, CI 55.7-84.3), 25 min = 59.6% (87.9, CI 76.3-99.4), 30 min = 55.6% (84.1, CI 76.8-91.5). MAP increased significantly after emasculation (P < 0.003) at 1 min (91 mmHg, CI 77.3-104.7) and 5 min (81 mmHg, CI 67.3-94.7). An increase HGS (P < 0.05), PTAm (Δ16%, P < 0.001), head up latency (P = 0.042), and frequency of limb retraction (P = 0.042), while a decrease in LA (P = 0.004), appetite (P = 0.043), and water consumption (P < 0.05) in days post-surgery were observed. Modulation of vagal tone occurs in response to castration under anesthesia and preservation of homeostasis days post-surgery.