There was no effect of ACTH or placebo administration in vivo on milk yield. There was no effect of the treatments or any significant interaction between treatment and sampling time on plasma IGF-1, on fat,protein, and lactose percentage, SCC, or the number of colony-forming units in the plate count agar, Mac- Conkey agar, and Baird Parker agar media (Table 2). There was a significant interaction between treatment and sampling time with regard to cortisol release, because in samples taken at 60 and 120 min, cortisol concentrations were higher after ACTH administration than those following the placebo treatment. The cortisol concentration returned to baseline levels 360 min after ACTH treatment and achieved similar values to those after the placebo administration (Figure 2). There was no effect of ACTH or placebo administration on the expression of the GHR, IGF1, IGF1R, IGFBP3, IGFBP5, BAX, or BCL2 genes, nor were there any effects of ACTH or placebo treatment on the percentage of cell proliferation (PCNA) and cell apoptosis (TUNEL) in mammary tissue (Table 3)