Cortisol response of gilts in tether stalls.

: Several experiments were conducted to evaluate serum cortisol concentrations and the circadian rhythm of this hormone in gilts tethered in stalls. Control animals were penned individually. In the initial experiment, 18 nongravid gilts were placed in tether stalls after being in either tether stalls or individual pens for 2 wk. No significant differences were found in serum cortisol concentrations. In a second experiment, 16 ovariectomized gilts were placed in tether stalls or individual pens for up to 5 wk. Estrus was induced during wk 3 and 4. During the first day in tether stalls, serum cortisol concentrations increased (P less than .05) and the circadian rhythm of cortisol was disrupted for 4 d. During estrus, the circadian rhythm of cortisol was interrupted for several days in the gilts, regardless of housing. After 4 wk, morning concentrations of cortisol were higher for gilts in tether stalls. The results indicate that: 1) the initial response to tethering varies according to previous penning and handling experience, 2) although the circadian rhythm of cortisol was either altered or disrupted during estrus, such disruptions were not influenced by type of penning and 3) tether stalls may chronically increase cortisol concentrations in gilts.