Figure 4.

Pathological changes in different treatment groups (hematoxylin and eosin staining, magnification 400x, 1 bar = 10 μm). No pathological changes were observed under normal conditions. When chickens suffered 5 h of heat stress, myocardial fiber fractures (↑) were observed in the heat stress (HS) group. Lesions in the rosemary + heat group showed acute degeneration (↓). At 10 h of heat treatment, karyopyknosis (△) and degeneration (↓) were observed in the HS group, whereas the hearts in the rosemary + heat group retained their basic structure, although fiber fracture (↑) and acute degeneration (↓) can be observed.