Figure 1.

Schematic representation of the experimental design presented in the current study. Late gestation cows were dried off at 46 d before calving and assigned to 1 of 2 in vivo treatments: cooling (CL) (n = 7); provided shade of the barn and active cooling by soakers and fans (blue); heat treatment (HT) (n = 7); only provided shade of the barn (red). Mammary biopsies were collected at 3 d (to capture the involution phase) and 35 (to capture the mammary redevelopment phase) and tissue explants were incubated in 1 of 3 in vitro treatments: (1) Basal (B): no prolactin or oestrogen; (2) CL-mimic (C): B + 20 ng/mL prolactin + 5.8 ng/mL oestrogen or (3) HT-mimic (H): B + 40 ng/mL prolactin + 2.9 ng/mL oestrogen.