Using time-series intervention analysis to model cow heart rate affected by programmed audio and environmental/physiological cues

This research is the first attempt at using time -series analysis to describe changes in the heart rate (HR) of free-ranging cows receiving programmed audio cues from directional virtual fencing (DVF™) devices designed to control the animal's location on the landscape as well as non-programmed environmental/physiological cues. Polar Accurex® devices were used to capture HR every minute between March 19-24, 2003 when three mature free-ranging beef cows previously habituated to DVF™ control were confined to a brush-infested area of an arid rangeland paddock. Global positioning system (GPS)electronics were used to locate each cow's location approximately every minute while it was in a 58 ha virtual paddock (VP™) and every second when it penetrated a virtual boundary (VB™). The cows never escaped through the VB™ though they penetrated it a total of 26 times in 11 different events at which time they received programmed audio cues lasting from 1 to 56 s. These data reveal that HR spikes from programmed audio cues all fell within the textbook range for cow HR (40-186 beats per minute, bpm). For both audio and selected evironmental /physiological events, HR spikes returned to pre-cuing "baseline" values in about one minute. However, the longest return time to baseline lasted (about 4 minutes) and this was for an environmental/physiological event. HR, animal location, weather and other electronic data should be measured at equally-spaced time intervals using a single time stamp so as to accurately associate HR changes with possible causes.