Abstract: Crib-biting (wind-sucking) might be a coping response of the horses to the challenges of
uncontrolled environmental events. Prevention of this stereotypic behaviour evokes
physiological responses consistent with increased stress. Reducing the incidence of cribbiting,
however, is important in order to prevent undesirable physical and behavioural
consequences (tooth erosion, altered gut function, gastric inflammation/ulceration, colic, etc.).
Common treatment of crib-biting is the application of a cribbing collar, which limits the
flexion of the neck making this stereotypic movement uncomfortable and difficult. Another
method, the modified Forssell"s operation, is becoming more and more popular amongst the
horse owners. It is based on the removal of the muscles used in crib-biting (m.omohyoideus,
m.sternohyoideus, m.sternothyrohyoideus) and the ventral branches of the spinal accessory
nerves. Surveys on the success of this surgical procedure have revealed inconsistent results,
and, contrary to the cribbing collar, its effect on the stress level have not been studied either.
The aim of our study was to determine whether the modified Forssell"s procedure is superior
to the cribbing collar treatment.
Differences in stress management was tested by a crib-biting provoking test, in which
surgically treated horses, crib-biting horses, crib-biting horses with cribbing collar, and
normal horses (those showing no stereotypies), altogether 56 horses were compared. In this
test, a food bucket had been placed out of the reach of the animal, from which titbits were
given 3 times. Behaviour and heart rate variability (HRV) of the horses were recorded and
analysed throughout the test. Hypotheses were tested by linear mixed model.
According to our results, both prevention methods (collar or surgery) inhibited crib-biting
successfully though not totally. Regarding behaviour and heart rate variability, horses
prevented from crib-biting (by collar or surgery) differed significantly from crib-biting and
normal horses but not from each other.
Normal horses were usually trying to reach the food-bucket while present and were standing
still afterwards, whereas the other three groups had not really made efforts to reach the
bucket, spent less time with resting, and performed or tried crib-biting. During the stress-test,
normal and crib-biting horses had shown good stress-adaptation to the challenge since their
HRV, after an initial increase, returned to the basal value by the end. On the contrary, HRV of
the two prevented groups remained elevated and showed large oscillations throughout. They
had not found a successful coping behaviour either.
Our results suggest that since prevention may significantly increase distress, the treatment in
itself, without changing the motivation of the horse to perform the replacement behaviour – it
seems to be unsatisfactory and insufficient. After prevention the motivation of the horse to
perform crib-biting should be addressed. In addition, considering that prevention by collar and
surgery had not resulted in any significant behavioural or physiological differences, the
superiority of the modified Forssell"s procedure might be questioned. However, the surgery
might be recommended if treatment with collar is ineffective.