The effect of floor type or relocation on calves’ pulsatile growth hormone and cortisol secretion

Abstract

To examine if hard floor or relocation to a new room affects the pulsatile secretion of growth hormone (GH) and cortisol in calves, we housed individually 12 calves on concrete floors and 12 on rubber mats for 67–74 days. Half of the calves in each pen were relocated to an identical but strange room. Serial blood samples were taken 24 h prior to and 24 h following relocation at 20-min intervals and were assayed for GH and cortisol. Both of the hormones had a clear ultradian pulsatile variation. We detected (mean±/se) 4.6±/0.6 GH pulses/24 h. GH concentrations peaked four times during the day and pulses were higher in daytime. Cortisol peaked 5.8±0.6 times/24 h. Cortisol concentrations were highest at feeding. No overall effects of flooring or relocation were found but calves on concrete floors had greater cortisol concentrations than on rubber mats, especially during the night.