Pigs with a body weight between 15 and 20 kg were vibrated in the vert
ical direction for 1 h at 2, 8, and 18 Hz, in combination with root me
an square (RMS) acceleration magnitudes of 1 or 3 m/s(2). Welfare and
stress were quantified by comparing heart rate characteristics during
a control period (2200 to 0600) before vibration exposure and during v
ibration (1000 to 1100). The level of maximum heart rate and number of
ventricular ectopic beats during vibration at 2 and 8 Hz in combinati
on with a RMS acceleration of 3 m/s(2) indicated a larger fear respons
e than at 1 m/s(2). Isocomfort contours based on mean heart rate durin
g vibration showed the greatest specific sensitivity of the pigs to vi
bration at a frequency of 8 and 18 Hz, especially in combination with
a RMS acceleration of 3 m/s(2). During transport, RMS acceleration sho
uld be less than 3 m/s(2) to protect pigs' welfare. Rigs were more sen
sitive to acceleration than to frequencies within the range of treatme
nts in this investigation. Although the response of the pigs in this e
xperiment fit within the model concept for adult humans and for domest
ic fowl, changes in heart rate are dependent on body weight.