Behavioural and physiological effects of 915 MHz microwave radiation on weaner pigs

Microwave radiation (915 MHz) was investigated as a form of supplemental heat for early weaned pigs. Infrared lamps were used as the industry control. Behavioural parameters including aggressive behaviour and activity level as well as average daily gain (ADG) were used as an indication of piglet health and welfare upon exposure to microwaves. Microwave exposure was found to cause a power level-dependent decrease in activity level (P < 0.05) in weaner pigs which diminished over a three week period of exposure. Average daily gain was not significantly affected (P > 0.05) by microwave exposure. No evidence of beat strew or discomfort was displayed by pigs in either treatment. Daily percent resting time was positively correlated (P < 0.05) with microwave power level, room temperature and skin temperature.

A subsequent study was carried out to investigate the basis of the microwave induced depression of activity. Serial blood samples were taken over a 24 hr period and plasma cortisol, glucose and melatonin levels were determined. Microwave radiation was found to induce a power level-dependent increase ( P < 0.05) in plasma melatonin and glucose concentrations. However, plasm cortisol concentrations were similar for microwave and infrared-exposed pigs (P > 0.05) indicating that microwaves were not causing stress-induced changes in behaviour or plasm melatonin and glucose.