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Research Training Scholarships

Fritha Langford

“Behavioural and electrophysiological characterisation of sleep in sheep and its application in animal welfare studies”

Major aims in the study of animal welfare are to try and understand the subjective mental experiences 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.

Sleep consists of two main phases: rapid-eye-movement (REM) and non- rapid-eye-movement (non-REM). REM and non-REM sleep are distinctly different physiologically and neurologically. During REM sleep an individual will dream, experience rapid, low-voltage brain waves, breathing is irregular, heart rate may be irregular and an individual may experience involuntary muscle jerks. Non-REM sleep is dreamless, brain waves are usually slow and of high voltage, breathing and heart rate are slow and regular, blood pressure is low, and the sleeper is relatively still. The majority of sleep is non-REM (80%) compared to REM (20%). Electrophysiological measurements, when combined with behavioural observations, provide a powerful means of characterising the states of sleep and wakefulness of animals.

When humans undergo an aversive, stressful, disturbing, worrying experience during wakefulness, their subsequent sleep can be affected. The ability to recognise and record sleep in sheep could provide a greater understanding of potential psychological and behavioural changes that occur after stressful/fatiguing husbandry procedures.

Fritha Langford, under the supervision of Dr Michael Cockram at the University of Edinburgh, conducted three experiments to determine the effects of routine husbandry procedures on sleep in sheep. Fritha hypothesised 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.

Fritha firstly investigated the effect on sleep of moving sheep from pasture to novel indoor housing. Secondly, she investigated the effects of stress and physical disturbance from an 8-hour road journey on sleep and rest during and after transport, and finally a third experiment was carried out to investigate the effects of reduced space allowances used during transport on resting behaviour during simulated maximum journey times and sleep post-treatment.

Behavioural and non-invasive electrophysiological recordings were used to characterise sleep in sheep. Patterns of REM and non-REM sleep were identified from postural changes and by spectral analyses of an electroencephalogram (brain cells communicate with each other through electrical pulses and an electroencephalogram (EEG) can be used to detect and record changes in these pulses), electro-oculogram (a record of the difference in electrical charge within the eyeball that may be used to measure eye movements) and electromyogram recordings (a test that is used to record the electrical activity of muscles – active, moving muscles produce an electrical current).

Changes were seen in the distribution, quality and quantity of sleep. Although there were no significant effects on the duration of REM sleep or Non-REM 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.

Fritha’s 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.

Information on whether transport and novel housing induce fatigue and reduce rest and sleep could be useful in formulating guidance on the welfare of sheep on farms, during transport, at market and a slaughter.

Published papers arising from Fritha’s project supported by UFAW:

Langford, F.M. and Cockram, M.S. 2010. Is sleep in animals affected by prior waking experiences? Animal Welfare. 19: 215-222.