Artemisia absinthium Improves Metabolic Efficiency and Reduces Heat Load in Heat-Stressed Spanish Goats: Comparative Effects with Ascorbic Acid

Heat stress is a major challenge to livestock production; affecting physiological homeostasis, metabolic function, and productivity. Although goats possess adaptive mechanisms to cope with elevated temperatures, prolonged heat exposure can compromise their health and performance. Antioxidant supplementation has been proposed as a nutritional strategy to mitigate the negative effects of heat stress; however, information on the efficacy of plant-derived antioxidants such as Artemisia absinthium remains limited. Therefore, this study evaluated the effects of ascorbic acid (ASC; vitamin C), Artemisia absinthium (ART; wormwood), and their combination on thermoregulatory, hematobiochemical, and gene expression responses in heat-stressed Spanish goats. Thirty-two adult female goats (4–5 years old; 48.8 ± 8.1 kg) were stratified by body weight and randomly assigned to four treatments (n = 8 per treatment): control (CON; no supplement), ASC (2 g/goat/day), ART (2 g/goat/day), and ASC+ART (1 g each/goat/day), and supplemented for 42 days under summer grazing conditions. Ambient temperature and relative humidity were recorded hourly to calculate the temperature–humidity index (THI). Rectal temperature (RT), respiratory rate (RR), and coat surface temperature (CST) were measured weekly. Blood samples were analyzed for packed cell volume, albumin, total protein, blood urea nitrogen, cholesterol, triglycerides, creatinine, thyroxine, and glucose. Peripheral blood mononuclear cells were isolated for gene expression analysis of HSP70, CAT, and GPX1 by quantitative PCR. Heat production was measured in a subset of goats using respiratory calorimetry. Physiological and blood data were analyzed using the MIXED procedure of SAS, whereas gene expression data were analyzed using one-way ANOVA. Mean THI, ambient temperature, and relative humidity during the study were 78.0 ± 0.44, 28.7 ± 0.69 °C, and 62.9 ± 1.08%, respectively, confirming sustained heat stress conditions. Rectal temperature was significantly higher in the ASC+ART group than in the other treatments (p < 0.05). Respiratory rate also differed among treatments (p < 0.01), with higher values in the ART and ASC+ART groups. The coefficient of heat tolerance was significantly affected by treatment (P = 0.033), and the ASC+ART group had the lowest value. Heat production per unit metabolic body weight was significantly lower in the ART group than in the other groups (p < 0.05). Triglyceride concentrations were significantly lower, whereas glucose concentration was significantly higher, in the ART group (p < 0.05). Expression of GPX1, CAT and HSP70 was significantly lower in supplemented groups than in the control group, indicating reduced oxidative stress. In conclusion, individual supplementation with Artemisia absinthium improved metabolic efficiency and favorably altered selected biochemical and molecular responses under heat stress, whereas ascorbic acid had limited effects. The combined treatment did not improve thermoregulation and appeared less favorable than Artemisia absinthium alone.