Pregnancy and parturition represent two important physiologic phases in female mammals, in which metabolic, behavioral, and endocrinologic changes should occur in perfect timing and interaction, leading to a normal course of gestation and the occurrence of parturition at term, allowing the birth of mature and viable offspring. The present study aimed to describe the hormonal changes recorded in the hair occurring in mares from pre-foaling to late pregnancy. The hair cortisol (C) concentrations did not show any significant variations throughout the study, while dehydroepiandrosterone (sulfate) (DHEA(S)) hair concentrations showed an increase from ST-1 to ST4 (p < 0.01) followed by a significant decrease at ST6 (p < 0.01). From ST7 to ST8, hair DHEA(S) concentrations increased significantly (p < 0.01). In ST7 the cortisol/DHEA(S) ratio*100 was higher than in the other sampling times (p < 0.01) except for ST0, in which the ratio was similar to ST7. Hair progesterone (P4), 17-β-estradiol (E2), and allopregnanolone (AlloP) concentrations showed similar patterns through time with the exception of some differences between them at the end of the sampling period. The results showed that hormones fluctuations in the hair mimicked those observed previously in plasma making hair interesting for retrospective studies both on mares and foals during gestation without invasiveness and adding a complementary tool in studying the feto-maternal relationship.

Cortisol and DHEA(S) are markers of allostatic load and resilience; as such, they may be added to the definition of performance measures alongside immunocompetence. We aimed at studying the potential carryover effects of management practices on growth performances and the interrelationship between the hypothalamic–pituitary–adrenal (HPA) axis, immunocompetence and performances during the preweaning period in dairy calves. This study consisted of first a retrospective cohort study and second a prospective study. Calves had their growth performances and disease occurrence recorded, and their hair steroids (T1 at 20.03 ± 0.39 and T2 at 50.83 ± 0.41 days from birth) and plasmatic and colostral immunoglobulin G (IgG) was measured by immunoassays. The occurrence of preweaning diseases and the duration of individual housing negatively correlated to body weight (BW) at 60 days and the hair cortisol-to-DHEA(S) ratio (HC/HDHEA(S)) (T2) was negatively correlated to the daily weight gain (DWG) (−0.36; p < 0.05), plasmatic IgG (plaIgG) and the apparent efficiency of absorption (AEA) (−0.41; p < 0.01). Our results confirmed that the occurrence of diseases during the preweaning period and individual housing duration are pivotal for calves’ growth. This prospective study highlighted a detrimental effect of allostatic load on immunocompetence and described a link between resilience and growth performances.