A method for quantification of jaw movements suitable for use on free-ranging cattle

Abstract

A data-logging system for the simultaneous measurement of the J-J interval (the interval between two successive jaw movements), the number of jaw movements and the number of pauses between jaw movements longer than 3 s was developed and tested in free-ranging cattle. The system, which consists of a transducer, a pulse generator and three heart rate memory units, is light-weight, compact, and carried on the halter of the animal. The transducer (a silicone tube filled with carbon granules) was fixed at the side of the lower jaw. The pulse generator converted changes in the electrical resistance of the transducer to two kinds of pulse signals: (1) jaw movements and (2) pauses between jaw movements longer than 3 s. The pulse signals were fed into three heart rate memory units, thus allowing J-J intervals, jaw movements and pauses between jaw movements longer than 3 s to be measured simultaneously. Grazing and rumination could be distinguished by a combination of the number of jaw movements and pauses between jaw movements longer than 3 s. The J-J intervals during grazing represent biting and chewing rhythms. The J-J intervals during rumination represent chewing rhythms and the pauses in jaw movement between swallowing of a bolus and regurgitation of the next bolus. The J-J intervals were more regular during rumination than during grazing. The present data-logging system should provide a further useful means for analyzing grazing and rumination in free-ranging cattle.