Behavioural and physiological responses of horses (Equus caballus) undergoing head lowering

Horse trainers often report that lowering the height of a horse's head so the poll is below the height of the withers can induce a calming effect during training. Four groups of horses were used in a two-part study to investigate the behavioral and physiological effects of head lowering in horses. In Part 1, Group A had no experimental stimuli applied and horses in Group B were trained to lower their heads when presented with a specific stimulus by the handler. The stimulus for head lowering was the application of downward pressure on the headcollar via the lead rope until the horse lowered its head such that its lips were approximately at mid-cannon (3rd metacarpal) height, whereupon the pressure was released. The stimulus was applied again if the horse raised its head during the 300s test period. In Part 2, Groups C and D were aroused until their heart rates exceeded than 100 bpm. Then, Group C had no further experimental stimuli applied whereas Group D lowered their heads as a response to the above stimulus for a period of 300s. Repeated measures analysis showed that there was no difference between the heart rate of Groups A and B or Groups C and D but that the heart rate of Groups A and B were lower than Groups C and D during the 300s post-arousal (P<0.001). The horses in Groups A and B were more likely to contact the handler (P<0.001), exhibit licking and chewing (P<0.001), rest a hindleg (P<0.001) and sniff the ground (P<0.001) than those in Groups C and D. The number of stimuli required to maintain the head in a lowered position was greatest during the first 30s (P=0.012 and P<0.001, Parts 1 and 2, respectively). The current study has shown that head lowering in horses does not influence cardiac responses, even after the horses had been aroused to have their heart rates above 100 bpm. Therefore, it is not a method that will aid in calming an aroused horse in training. Also, contrary to popular belief, there was no association with licking-and-chewhead lowering, nor with these behaviors and response acquisition.