Effect of Water Restriction on Physiological Parameters and Reproductive Hormones in Suffolk Down Ewes in Chile

Abstract

The water crisis in Chile, intensified by a prolonged megadrought lasting over a decade, has severely affected Mediterranean dryland areas where sheep are the predominant livestock due to their resilience to adverse environmental conditions. However, studies show that moderate to severe water restriction impacts physiological parameters and reproductive hormone secretion, with effects varying depending on the breed's adaptive capacity. This study evaluated the effect of water restriction on physiological indicators and reproductive hormone production in ewes from the Chilean Mediterranean dryland. Eighteen healthy, non-pregnant Suffolk Down ewes during the breeding season were divided into three groups: control (ad libitum water), G1 (–20% ad libitum water), and G2 (–40% ad libitum water). The trial lasted 36 days, with estrous cycles synchronized prior to initiation. General physiological parameters, biochemical levels, and blood hormone concentrations were measured during the final week. G2 showed a significantly higher rectal temperature (38.9 ± 0.3 °C) and hematocrit (29.7 ± 1.6%) compared to the control group (38.5 ± 0.3 °C and 27.0 ± 1.1%, respectively). G1 presented significantly lower plasma creatinine (0.5 ± 0.1 mg/dL) than the control (0.7 ± 0.1 mg/dL). Progesterone levels were significantly higher in G2 (6.3 ± 2.7 ng/mL) than in the control (2.5 ± 1.1 ng/mL), indicating a possible alteration of the endocrine axis. No significant differences were observed in respiratory rate (44–45 RPM), body condition (2.9–3.4), basal glucose (46.5–53.2 mg/dL), BUN (25.6–26.8 mg/dL), total proteins (7.2–8.4 g/dL), FSH (0.2–0.5 mIU/mL), or 17β-estradiol (14–15.8 pg/mL). This study highlights the biological effects of water stress in Suffolk Down ewes in Chile and their physiological responses to extreme environments.