Triaxial accelerometers for recording grazing and ruminating time in dairy cows: An alternative to visual observations

Abstract

The aim of this study was to validate the recordings of a commercial triaxial accelerometer (HOBO Pendant G data loggers) with respect to visual observations of grazing and ruminating time of dairy cows. Seven lactating Holstein cows with a mean body weight of 602 45 kg were used for the study. Grazing and ruminating times were recorded using HOBO loggers (31.5 hours of total observations for grazing and ruminating) that were attached to the lateral-medial side of the jaw using a strap attached to the head of each cow in a position such that the X-axis was parallel to the ground, the Y-axis was perpendicular to the ground pointing upward, and the Z-axis was parallel to the ground pointing away from the sagittal plane; these relative positions were defined when the cow was in a natural head-up position. Median acceleration (m/s2) readings in the X-axis >0.175 and <0.95 indicated grazing activity, whereas readings in the Z-axis > 0.275 and <0.0875 indicated ruminating activity. The degree of vertical tilt ( Y-axis) was used to determine grazing position (readings >0 and <61 ) and ruminating (readings >0 and <25.8 ). Results showed a significant (P < 0.001) relationship of estimated grazing time against visual observations when acceleration (X-axis) was used only; nonetheless acceleration (Z-axis) was not significant (P > 0.05) for estimating ruminating time. When acceleration and tilt were used for estimating grazing (X- and Y-axis) and ruminating (Z- and Y-axis) time, the slope in both showed a significant (P 0.001) relationship. The prediction R2 in both activities indicated that acceleration (X- and Z-axis) and tilt (Y-axis) of HOBO loggers explained 0.961 and 0.945 of the variance in visual observations per cow/day. Therefore, the validation of the HOBO loggers was successful on a per cow/day and per day basis.