A 3·5 MHz linear transducer was used to assess the motility of the reticulum in 30 healthy, standing, non-sedated cows while they were at rest, eating, ruminating and under stress. The ultrasonographic examinations were made over periods of nine minutes and video recorded for analysis. The reticulum contracted in a biphasic pattern while the cows were resting, eating or stressed. The first contraction was incomplete and was followed by a period of incomplete relaxation. A complete second contraction occurred immediately afterwards, followed by an interval of complete relaxation and the return of the organ to its original position. When the cows were ruminating, a regurgitation contraction, which was incomplete, occurred immediately before the biphasic contraction. The number of reticular contractions in a nine-minute period was largest when the cows were eating (13·9 contractions, or approximately 1·5 per minute) and smallest when they were stressed (9·3 contractions, or approximately 1 per minute). The duration of the first reticular contraction was shortest during rumination (2·4 seconds) and longest when the cows were eating (3·0 seconds). The interval between two biphasic contractions was shortest when the cows were eating (31·6 seconds) and longest when they were stressed (53·8 seconds).
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