Avoidance of tape-recorded milking facility noise by dairy heifers in a Y maze choice task

The effect of noise pre-recorded from a commercial milking facility on the choice behaviour of dairy heifers in a Y maze was examined. Sixteen animals were individually trained to associate noise onset with a particular maze arm and no noise (quiet) with the other maze arm. After a maze familiarisation period, each heifer was exposed to a mixture of training trials, where access to only one maze arm was made available, and choice trials, where both maze arms were available. In order to reduce possible interference from animals' original side preferences or response patterns under two-alternative choice situations, training and choice trials were interspersed and the noise stimulus was presented in the maze arm first chosen after familiarisation. Over 11 exposures to the maze across 3 days, choice of maze arm (during choice trials), avoidance behaviour (time taken to enter maze arm, number of stops, handler intervention required) and heart rate (HR) were measured. Results showed that the percentage of heifers that chose the quiet arm changed significantly (p < 0.01) from 31.3% to 81.3% over the course of the experiment. In addition, during training trials, animals took longer (p < 0.05) to enter the maze arm, stopped more, required more handler intervention when entering and were more restless in the noise compared to the quiet arm. During training trials there was also a trend (p = 0.06) indicating some increase in HR during noise trials compared to quiet trials. Overall, the results of this experiment indicate that milking facility noise is fear-provoking for dairy heifers and that they will learn to avoid this noise when given the opportunity. The experiment has also demonstrated successful use of this Y maze choice methodology for assessment of environmental stimuli in dairy heifers (previously Y maze methods have only been used to assess handling and husbandry practices in cattle).