The effects on sheep welfare of motion produced by a ship during sea transport have not been reviewed, but there is comprehensive knowledge of adverse effects in humans. The overall aim of this project was to describe the impact that roll, pitch and heave motions have on sheep welfare through behavior and heart rate measurements. A novel method was developed to create these motions using a programmable simulator platform that generated roll and pitch motions replicating ship movements, and comparing regular and irregular movement sequences. An electric forklift was used to produce heave motion.
The first study measured individually Roll, Heave and Pitch. Heave reduced the time that sheep spent ruminating, compared with the other three treatments (P < 0.001). The two sheep spent more time during Heave with their heads one above the head of the other (P < 0.001) compared with sheep in roll, pitch or control treatments, and looking towards their companion (P = 0.02) compared with sheep in roll and control treatments. Sheep spent more time during Heave standing with their back supported on the crate (P = 0.006) and less time lying down (P = 0.01) compared with sheep in roll, pitch or control treatments. Roll caused more stepping motions than pitch and control (P < 0.001). Heave and Roll had increased heart rates and reduced inter-beat intervals, compared to Control (P < 0.001). The inter-beat intervals of sheep in the heave treatment had an increased ratio of low to high frequency duration (P = 0.01), indicating reduced parasympathetic control of stress responses. Therefore Heave and Roll caused stress, with sheep experiencing Roll requiring apparently coping better by regular posture changes and Heave causing the sheep to seek close presence to their companion.
The second study measured whether Roll and Heave affects sheep feed intake, behaviors, and heart rate measurements, and whether providing antiemetic drugs attenuates motion effects in the sheep. There was no evidence of effects of the motion on feed intake, but the Heave treatment made the sheep eat faster (P = 0.006), with fewer mastication bites (P = 0.004), which could reduce the efficiency of digestion. Antiemetic provided limited evidence of improved balance, since the sheep spent less time with their head against a dividing mesh in the crate (P= 0.01), and they increased prehension biting rate in the Heave treatment (P = 0.002). Sheep in the Heave treatment spent longer with their head against the mesh than those in the Control treatment (P = 0.009). It is concluded that simulated ship motion did not cause reduced feed intake over short periods, but that there was limited evidence that the motion had adverse effects on balance which could be attenuated by an antiemetic.
The third study measured the effects of regular and irregular sequences of roll and pitch, or a combination of the two on sheep feed and water intake, heart rate measurements and body posture. Feed intake was increased by irregular sequences in the combined Roll and Pitch motion (P=0.04). The two sheep spent more time during Irregular sequences with their heads one above the other (P= 0.001), and facing down (P = 0.001) than Regular sequences. The combined Roll and Pitch also increased the time sheep spent with their heads down (P = 0.007) compared to Roll and Pitch motions. Sheep spent more time during Irregular sequences standing with their back supported on the crate (P < 0.001) or kneeling (P = 0.03) compared to Regular sequences. Irregular sequences, the combined roll and pitch and the interaction between the two produced more stepping behaviour. Sheep exposed to Irregular sequences of combined Roll and Pitch had increased heart rates (P < 0.001). In the combined Roll and Pitch motion the ratio of Low to High Frequencies was increased (P = 0.007) by Irregular compared to Regular sequences. Therefore Irregular sequences and the combination of Roll and Pitch caused stress, loss of balance and more affiliative behaviour between sheep.
The final study measured the effects of regular and irregular combined roll and pitch motions and a barrier to separate sheep on heart rate measurements and behavior. Stepping to avoid loss of balance was more frequent when sheep had no barrier (P < 0.001) and during irregular motion (P < 0.001). Without the barrier (P = 0.03) and during irregular motion (P < 0.001), sheep spent more time with their head under or above the other sheep compared to barrier in place, and control motion. During irregular motion they supported themselves more against the crate (P <0.001) compared to Regular and Control. When the barrier was removed there was increased agonistic behavior, including pushing with the body (P = 0.02), butting (P = 0.02) and evading the other sheep (P = 0.001). Sheep ruminated more when the barrier was in place (P = 0.02). There was evidence of stress caused by removal of the barrier since the square root of the mean of the sum of the squares of differences between successive inter-beat intervals (RMSSD) and the number of pairs of successive inter-beat intervals (NN50) and rumination were all reduced. Irregular sequences increased the ratio of high to low frequency beats (P = 0.03). The ratio of low to high frequency beats was highest (P = 0.005) and the RMSSD and NN50 were lowest (P < 0.001) during irregular motion and no barrier, indicating that sheep were most stressed in this combination of treatments. Therefore when providing an opportunity for sheep to interact during irregular motion caused stress and body instability.
Our findings provide sufficient evidence to conclude that sea transport motions represent a potential stressor to sheep