NUTRITIONAL MANAGEMENT OF LIVESTOCK DURING HEAT STRESS

Abstract

Heat stress is a significant environmental challenge, as it reduces livestock productivity by compromising thermoregulation, metabolic equilibrium, and oxidative balance. This study examined responses of dairy cows, goats, and broilers to heat stress (temperature–humidity index ≈ 82) for 21 days under different nutritional management treatments, focusing on relevant physiological variables, performance parameters, and markers of oxidative stress. A total of 72 animals (24 animals per species) were divided randomly into four dietary treatments: heat stress control (HS-Control), heat stress with electrolyte supplementation (HS-ES), heat stress with antioxidant supplementation (HS-AO), and heat stress with energy-dense diet (HS-ED), with six animals per treatment per species. Heat stress substantially decreased in dry matter intake (15.9 ± 0.6 kg/day) and milk yield (19.8 ± 0.7 kg/day) compared with that of any other group, but HS-ED significantly increased milk yield by 24.6 ± 0.6 kg/day (P < 0.001). The rectal temperature and cortisol concentration were also lower in the nutritionally supplemented groups than in the control groups. In goats, HS-ED increased average daily gain (0.086 ± 0.005 kg/dY to 0.124 ± 0.006 kg/dAY) and feed to gain ratio (13.0 ± 0.4 to 10.4 ± 0.3; P <.001). Body weight gain of broilers increased from 52 ± 2 g/day in HS-Control to 67 ± 2 g/day in HS-ED, and feed conversion ratio improved from 1.77 ± 0.02 to 1.55 ± 0.01 (P < 0.001). Antioxidant supplementation significantly reduced malondialdehyde levels and increased superoxide dismutase activity in animals of all species. The general conclusion was that nutritional measures, particularly high-energy, antioxidant-rich diets, were effective means to alleviate the adverse effects of heat stress and to improve productivity and physiological homeostasis in farm animals.