Mitigating heat stress in Garut lambs: Synergistic effects of Lemuru fish oil, vitamin E, and selenium on antioxidant defense, hematology, and physiological responses

Background and Aim: Tropical climates expose livestock to prolonged heat stress, leading to compromised health, growth, and productivity. Nutritional interventions using omega-3 fatty acids and antioxidants may improve resilience in such environments. This study evaluated the effects of lemuru fish oil (LO), vitamin E, and selenium – individually and in combination – on hematological, physiological, antioxidant, and growth parameters of Garut lambs exposed to tropical heat stress. Materials and Methods: Forty male Garut lambs (23.52 ± 2.51 kg; 9–10 months old) were randomly assigned to five dietary groups: Control (CNT), LO (6%, LO), LO + 500 IU Vitamin E, LO + 0.5 ppm selenium, and LO + both Vitamin E and selenium (LOES). The 60-day trial took place during the dry season under severe to extreme heat stress conditions (temperature-humidity index: 25.13–40.07). Parameters assessed included nutrient intake, physiological responses, blood hematology, antioxidant status, and growth performance. Results: Supplementation with LO and antioxidants significantly improved hematological indicators (e.g., hemoglobin), enhanced antioxidant defenses (e.g., increased superoxide dismutase SOD and glutathione, reduced malondialdehyde MDA, and cortisol levels), and stabilized physiological responses (e.g., lower rectal temperature and heart rate). The LOES group showed the most pronounced improvements: SOD increased by 107%, MDA decreased by 62%, and cortisol levels were reduced by 28% compared to the CNTs. However, no significant differences were observed in average daily gain or feed efficiency. Conclusion: The combination of LO with Vitamin E and selenium effectively mitigated heat-induced oxidative and physiological stress in Garut lambs. Although growth parameters remained unchanged, the improved physiological and antioxidant status suggests that these supplements may be valuable functional feed additives for enhancing animal welfare and resilience under heat stress. Further research is warranted to investigate the long-term effects on productivity and reproduction. Keywords: antioxidants, Garut sheep, heat stress, hematology, lemuru fish oil, omega-3, oxidative stress, physiological response, selenium, Vitamin E.