The effect of low energy electric shock on cortisol, β-endorphin, heart rate and behaviour of cattle

Electrical stimuli are used increasingly to confine cattle, whether through conventional electric fencing or the development of ‘virtual’ fencing systems. Two experiments were conducted to assess behavioural, heart rate and stress hormone responses of cattle to electrical stimuli typically used in such confinement applications. In the first experiment, 30 steers (18-months old; n = 10 per treatment) were held in a handling crush for 15 min after receiving one of the following treatments: nothing (control); delivery of three shocks at 2 s intervals (600 V, 250 mW); and restraint in a head bail for 3 min. Plasma cortisol and β-endorphin concentrations were measured at 0, 5, 10, 15 min, 1, 2, 3, and 4 h. In a second experiment, heart rate and behaviour were measured in 17 heifers (18 months of age) subjected to one of the following treatments whilst held in a crush for 10 min: nothing (control; n = 5); delivery of three shocks at 2 s intervals (600 V, 250 mW; n = 6); and restraint in a head bail for 3 min (n = 6). Cortisol and β-endorphin concentrations did not differ between treatments (P > 0.05). Whilst animals were receiving the treatments, heart rate was lower when head restrained compared with shock or control treatments (P = 0.009) and did not differ between control and electric shock treatments (P = 0.35). Upon release from the crush, heart rate was higher in shock and head restrained treatments than the control treatment (P = 0.005). Animals receiving the electric shock treatment tossed their heads more frequently whilst in the crush than control animals (P = 0.012) but did not differ from the other treatments in the number of vocalisations, tail swishes, steps back and forward, head tilts and head turns. There was a significant effect of treatment on flight time (P = 0.005); animals receiving the electric shocks were faster to leave the crush than control animals (P = 0.005) and there was no difference between head restraint and shock treatment (P = 0.86). In 10 min following release from the crush, there was no treatment difference in the time to start feeding. This study suggests that the stress response of cattle to low energy electric shocks is minimal and is similar to that induced by restraint in a crush.