Nicotinamide Riboside Supplementation Alleviates Heat Stress‐Induced Testicular Damage and Improves Semen Quality in Boars

Rising global temperatures and increasing extreme weather events have profound and widespread health impacts, particularly on vulnerable populations and sensitive organs. This study aimed to investigate the impact of HS on testicular NAD⁺ metabolism and assess the potential of NAD⁺ precursor supplementation in alleviating heat stress (HS)-induced reductions in semen quality. This study aimed to investigate the impact of HS on testicular NAD⁺ metabolism and assess the potential of NAD⁺ precursor supplementation in alleviating HS-induced reductions in semen quality. In this study, 24 Rongchang boars were randomly divided into three groups: a control group (CON), HS group, and HS supplementation with nicotinamide riboside group (HS-NR). After the initial feeding phase, the boars were exposed to either a thermoneutral or HS environment for 2 weeks. In this study, we identified NAD⁺ deficiency as a hallmark of testicular damage under HS. Supplementation with NR effectively restored testicular NAD⁺ metabolism. NR supplementation also improved semen quality, reduced spermatogenesis defects, and attenuated oxidative stress and inflammation induced by HS. These findings highlight the potential of NAD⁺ precursors as a promising nutritional strategy to mitigate the adverse effects of HS on male reproductive health.