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    Characterising the responses of farm mammals to a thoracic squeeze and the relationship to tonic immobility : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Manawatū, New Zealand
    (Massey University, 2023) Holdsworth, Sophia Ellen
    Applying compression to the thorax of newborn farm mammals causes immobility accompanied by reduced responsiveness. Traditionally, this response was proposed to arise in neonatal foals due to the ‘thoracic squeeze’ mimicking the compression occurring during birth. Recent findings regarding the responses to the squeeze suggest a link to Tonic Immobility (TI). TI is a temporary and reversible state of reduced responsiveness and immobility with characteristic physiological changes. It is elicited by the collective actions of handling and sustained physical contact with additional pressure (restraint) and may be facilitated by inversion. TI is reported in young and adult animals of numerous species. The aim of this thesis was to examine whether responses to the thoracic squeeze are consistent with TI. First, behavioural responses to a squeeze were explored in lambs, with a focus on determining whether responses persisted beyond the neonatal period. Cortisol responses of healthy neonatal piglets to the squeeze were then investigated to explore similarities in Hypothalamic-Pituitary-Adrenal responses between the squeeze and TI. The final study examined electroencephalographic (EEG) responses of healthy neonatal piglets to a thoracic squeeze under light anaesthesia, to determine whether the squeeze causes changes in brain activity or exerts anti-nociceptive effects such as those reported during TI. The results demonstrated that responses to a thoracic squeeze persist beyond the neonatal period in lambs, and responses are generalised across multiple mammalian species. Furthermore, cortisol responses of piglets to a thoracic squeeze followed a similar pattern to that previously observed during TI in other species. Also consistent with some TI studies, the initial handling and restraint required to apply the squeeze appeared to induce the cortisol response in piglets. No inferences could be made about the effects of a thoracic squeeze on state of awareness in neonatal piglets, or the squeeze’s effect on nociception due to methodological limitations. Nevertheless, the results of this research support the hypothesis that the thoracic squeeze may be classified as a stimulus for inducing TI. Further work is required to characterise the effects of the squeeze on awareness and nociception and to explore the affective experiences of animals subjected to the squeeze.
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    Tonic immobility by dogs : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science in Veterinary Ethology at Massey University
    (Massey University, 1993) Ong, Rae Ming
    Tonic immobility (TI) is a state of relative immobility induced by restraint and presumed to function as a terminal defensive reaction. Although TI has been reported in a wide spectrum of species ranging from invertebrates to mammals, there have been very limited studies on TI by dogs. The aim of this thesis was to determine the susceptibility and characteristics of TI in dogs so that the feasibility of using TI as a humane, quick, easily reversible, non-chemical and safe method of restraint for veterinary procedures could be assessed. In an initial survey, 132 dogs were tested twice. Once by inversion and 30s restraint in the lateral position and once with an additional treatment (stroking, scruffing, blanket over head, cuff around ears or light into eyes) during the 30s restraint. Based on the criterion of remaining in the position restrained, without lifting its head off the test surface, for a minimum of 10s after release from restraint, 10 of the 132 dogs (7.6%) exhibited TI. The characteristics of the dogs during TI were similar to those reported in other species, as the dogs remained very still, with the exception of occasional repositioning of heads and limbs, muscle tremors, twitches and paw movements. Swallowing, lip licking, blinking and occasional periods of eye closure were also observed but dogs had their eyes open throughout most of the TI episodes and appeared to be continually monitoring their environment as eye and ear movements, muscle twitches and changes in respiration rate were observed in response to auditory and other stimuli. Many TI episodes were not terminated by intense stimulation such as loud auditory stimuli or physiological testing that included pinching between the dog's toes and inserting a thermometer into the dog's rectum. Respiration rate, heart rate, withdrawal reflexes and temperature were monitored on these dogs. These physiological parameters were all within normal limits. Susceptibility to TI appeared to be a dog effect rather than a technique effect. Timid dogs or dogs that eliminated during testing were more susceptible to TI, indicating that susceptibility may be related to the dog's temperament or fearfulness. It was also found that proestrous bitches were more susceptible to TI than the other dogs. A potentiation effect with repeated testing was observed when the intertrial interval was between 20-80s. No order or carry-over effect was however found when a 3 min intertrial interval was used. No difference in susceptibility to TI was found between techniques but the cuffing technique resulted in longer TI durations than the others. Results should however, be interpreted with caution due to the small number of dogs exhibiting TI. More extensive investigations of the characteristics and physiological changes during TI and the effect of individual variables on TI susceptibility and durations are also required to determine the safety and extent of procedures that may be conducted while dogs are in TI. The results from this initial study are promising as they show that dogs do exhibit TI. The duration, characteristics and physiological changes observed during TI also indicate the potential for using TI as a quick, non-chemical, easily reversible and safe method of restraint in some dogs, for routine clinical examinations or even veterinary procedures.