A Reversal of Heat Stress-Induced Impairments in Boar Endocrine and Reproductive Function by Complex Liposomal Vitamin, Zinc Gluconate, and Betaine Supplementation.

Rising global temperatures are increasing the risk of heat stress (HS), with breeding boars being particularly vulnerable due to the high sensitivity of testicular function to elevated temperatures and oxidative stress. This pilot study evaluated whether a complex liposomal preparation containing vitamins A, D3, E, and C, zinc gluconate, and betaine could mitigate HS-induced impairments in boar endocrine function and semen quality. Nine clinically healthy boars (Landrace, Piétrain, and Maxter; n = 3 each; 2-4 years old) were studied across three consecutive stages: euthermic conditions (17°C-23°C), experimentally induced HS (25°C-30°C; 75%-85% relative humidity), and HS with dietary supplementation (20 mL/day of liposomal emulsion). At the end of each stage, cortisol and thyroxine (plasma), testosterone (circulating and seminal), sperm kinematics, and antioxidant enzyme activity in ejaculates were evaluated. Heat stress significantly increased circulating cortisol (+45.9%) and thyroxine (+15.5%), while reducing testosterone concentrations in blood (-21.7%) and seminal plasma (-52.2%). It also decreased total sperm number (-26.8%), progressive motility (-14.2%), and most kinematic parameters (p < 0.05). Supplementation restored testosterone levels in blood and seminal plasma, and reduced blood cortisol and thyroxine concentrations (p < 0.05). Ejaculate volume, sperm concentration, and total sperm count increased by +18.0%, +26.8%, and + 53.4%, respectively (p < 0.05), while motility and kinematic parameters improved significantly. Antioxidant defences also rebounded, with glutathione peroxidase and catalase activities increasing by 61.4% and 29.8%, respectively (p < 0.05). Most parameters analysed returned to baseline ranges, with several exceeding the values observed under euthermic conditions. In conclusion, dietary supplementation with a complex liposomal preparation containing vitamins (A, D3, E, and C), zinc gluconate, and betaine effectively reversed the adverse effects of induced moderate HS on endocrine and reproductive function in boars, underscoring its potential as a valid strategy for maintaining or even boosting male fertility under thermal stress.