PHYSIOLOGY, ENDOCRINOLOGY, AND REPRODUCTION Physiological Changes to Transient Exposure to Heat Stress Observed in Laying Hens

approximately the same number of eggs/hen housed to 80 wk; however, little is known about differences in per-formance during heat stress (HS). Two experiments were performed. The first experiment evaluated intestinal cal-cium uptake (CaT), heat shock protein-70 (HSP70) liver expression, and endocrine status in the 3 strains under heat stress in response to 1 h of transient exposure to high temperature before onset of 18 h of HS. The second experiment evaluated the differences between W-36 and W-98 in acid-base status observed at 2 different ambient temperatures. The HSP70 and CaT data were analyzed as a completely randomized design (CRD) using a 3 × 2 factorial with strain as a 1 factor and preexposed and control treatments as the other. Estrogen and progester-one data were analyzed as a CRD using repeated mea-sures in a 3 × 2 × 2 factorial with strain as a the firs