In contrast, chronic stress is established when a continuous or cumulative stressor is maintained. In that case, the cortisol concentration remains significantly higher than the basal concentration (Mormede et al., 2007; Kassahn et al., 2009; Brown and Vosloo, 2017), causing cumulative and negative effects for animals. In general, large amounts of exogenous glucocorticoids reduce milk yield (van der Kolk, 1990; Ollier et al., 2016; Ponchon et al., 2017). Indeed, other studies have shown that glucocorticoid administration was also associated with decreases in the immune response and failure of the HPA axis (Kassahn et al., 2009; Caroprese et al., 2010; Larzul et al., 2015). However, in the present study, no effect was observed of ACTH administration and cortisol increase on IGF-1 release in plasma, milk yield or milk quality. Similarly, other studies that also used ACTH or glucocorticoid administration did not observe any negative effect on either milk quality or milk yield in dairy goats (Stewart and Thompson, 1984; Anderson et al., 1991; Shamay et al., 2000). For these reasons, we proposed to study the effect of high levels of cortisol in mammary tissue in vitro to verify the possible local effect of cortisol without affecting other mechanisms, tissues or glands involved in complex responses to stress