Table 1.
Ethogram of lambs with different postures and level of activity and their corresponding scores.
Fig 1.
Behavioural and polysomnographic recording of sleep in newborn lambs.
Newborn lambs were used in the study (A), the electrode sites were shaved (A, a) and after the electrodes were applied using a medical plaster (A, b), all equipment was protected by handmade protective fabric (A, c and d). High-resolution camera equipped with an infrared emitter to monitor the lamb’s behaviour (B, a). Gold-plated disc electrodes (B, b,1) were used to record EEG, EOG and EMG. These electrodes were connected to two separate devices: the two-channel Actiwave EMG device (B, b, 2) and the four-channel Actiwave EEG/ECG device (B, b, 3) (CamNtech Ltd in Cambridgeshire, UK). C. Demonstration of electrode placement on the head and neck of the lamb.
Fig 2.
Locomotor activity patterns in lambs at birth and after the onset of rumination.
Actograms illustrative of the locomotor activity of four representative lambs, at birth (A) and after rumination (B). The duration of activity (min) was measured every hour for each animal and then averaged for all lambs (C: at birth and D: after rumination). The intensity of the grey colour increases with increasing activity level. The black and white bars situated at the top of the actograms correspond respectively to the dark and light phases of the natural LD cycle.
Fig 3.
Duration of rest and activity periods.
Mean (± SEM) of total duration of rest and activity during the 24-hour (A), Night (B) and Day (C) of each recording period. The duration of rest (scores 0, 1, 2 and 3) and activity (scores 4, 5 and 6) were calculated during the 24-hour, Night and Day periods during each phase. Significance levels were set at p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), p < 0.0001 (****).
Fig 4.
Polysomnographic traces of states of vigilance in newborn lambs.
A- quiet wakefulness, B- active wakefulness. C- drowsiness (light sleep). D- NREM sleep (deep sleep). D- REM sleep. E- Rumination. F- Rumination+NREM sleep. EEG waveforms from frontal and parietal electrodes are represented by EEG1 and EEG2, respectively. EOG1 and EOG2 are the electro-oculogram waveforms of the right and left eye electrodes, and EMG1 and EMG2 represent the electromyograms of the splenius and masseter muscles, respectively. PSG signals were recorded in 30-second periods.
Fig 5.
Distribution of vigilance states.
Hypnograms representative of the two recording periods (A and B), presenting the distribution of vigilance states (wakefulness, drowsiness, NREM sleep, REM sleep and rumination) during the recording periods illustrated. The increase in colour density indicates the transition from wakefulness to sleep stages, with the black and white bars corresponding to the dark and light phases of the L/D cycle, respectively. The mean (± SEM) proportion of vigilance states was calculated and averaged over the night and day of each recording period (C and D). Significance levels were set at p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), p < 0.0001 (****).
Fig 6.
Comparison of the mean (± SEM) percentage of time spent in each vigilance state during night and day (A and B), the mean (±SEM) number of episodes of each vigilance state (C and D) and the mean (± SEM) duration of episodes of each vigilance state (E and F), recorded during the first recording period (at birth) and the second recording period (after rumination). The percentages of each vigilance state, duration and number of episodes were calculated for each animal and then averaged for all animals separately for night and day. The significance levels were set at p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), and p < 0.0001 (****).
Fig 7.
Total sleep duration at birth and after rumination.
Comparison of the average percentage (± SEM) of total sleep time (TST) (the combination of drowsiness, NREM and REM sleep percentages) during the night and day of the two study recording periods (at birth vs after rumination). The TST percentage was calculated and averaged separately for the night and day periods. Significance levels were set to p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), p < 0.0001 (****).
Fig 8.
Correlation between behavioural postures and vigilance states.
Average percentage (± SEM) of vigilance states in each behavioural score, during the initial period (at birth) and the second period (after rumination).