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Title: Behavioural and electrophysiological characterisation of sleep in sheep and its application in animal welfare studies
Author: Langford, Fritha
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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Major aims in the study of animal welfare are to try and understand the subjective mental experience of animals, to develop methods to assess their responses to changes in mental state and to use this information to enhance animal welfare. One of the most profound changes of mental state observable in all mammals is the change between wakefulness and sleep. Electrophysiological measurements, when combined with behavioural observations, provide a powerful means of characterising the states of sleep and wakefulness of animals. The spectral components of an electroencephalogram (EEG) reflect the differences in the electrical activity of the brain between sleep and wakefulness. When humans undergo an aversive, stressful, disturbing, or worrying experience during wakefulness, their subsequent sleep can be affected. The present series of investigations examined the hypothesis that sheep exposed to aversive husbandry procedures would experience disturbances to their subsequent sleep. A sleep disturbance might provide an indication of the effect of an aversive husbandry procedure on the mental state of a sheep, that would not otherwise have been detected using conventional methods such as behavioural observation, blood biochemistry and heart rate. Non-invasive electrophysiological hardware and software developed and used for human sleep studies, was adapted and used to study sleep in sheep. To assess the effectiveness of surface electrophysiological recordings to detect changes in the electrical activity of the brain of a sheep, three validation studies were carried out. They consisted of a) the post-mortem passage of electrical current through the head of a sheep; b) changes in EEG in response to depth of general anaesthesia and c) the EEG responses of a sheep in a sleep posture to an auditory stimulus. The method was then applied to characterise the sleep of six, housed, adult ewes. Three percent (± 0.2) of a 24-h period was spent in rapid-eye-movement (REM) sleep and 15% (± 2.4) was spent in Non-REM sleep. Three experiments were undertaken to assess the effects of potentially aversive husbandry procedures on subsequent sleep. These consisted of a) movement to a novel environment; b) an 8-h road transport journey and c) a 29-h space Thesis Abstract restriction period (simulating times and space allowances used during road transport). Changes were seen in the distribution, quality and quantity of sleep. Although there were no significant effects on the duration of REM sleep or NonREM sleep, in two experiments, an increase in the number of REM sleep bouts was seen post-treatment. In all experiments, a post-treatment increase in the percentage of slow waves was seen in Non-REM sleep. This work provided a greater understanding of the impact of potentially aversive husbandry procedures on rest and sleep in sheep. All three of the potentially aversive husbandry procedures used as experimental treatments were associated with changes in subsequent sleep that may have been indicative of aversive experience during wakefulness. Although the changes in sleep found post-treatment were not large, they were consistent and reliable and therefore the methodology has potential for use in other applied animal welfare studies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available