Effects of N-acetyl-L-cysteine on sperm quality during chilled storage of Maguan hornless goat semen

The Maguan hornless goat is a valuable indigenous goat breed in Yunnan Province, China. As a rare and endangered genetic resource, its population protection and breeding are challenged by numerous challenges, particularly during artificial insemination procedures. During chilled storage, sperm generate excessive levels of reactive oxygen species (ROS), which disrupt the integrity of the sperm plasma membrane, damage the celluar structures, and lead to a decline in semen quality. This study investigated the effects of different concentrations (0, 5, 7, 9 mM) of N-acetylcysteine (NAC) on the chilled storage of semen collected from Maguan hornless goats. Semen was collected from four healthy rams with normal reproductive performance. The different concentrations of NAC were added to the semen diluent, and the samples were diluted 10-fold prior to storage at 4 °C for up to 72 h. After defining storage intervals, sperm kinetics, antioxidant gene transcription, and oxidative stress-related enzymatic activity were analyzed. Results showed that sperm samples extended in diluent supplemented with 7 mM NAC and subjected to 72 h of chilled storage at 4 ℃ exhibited improved antioxidant levels. This approach also reduced sperm apoptosis, enhanced membrane integrity and mitochondrial membrane potential, and suppressed the expression of pro-apoptotic genes (BAX, Caspase 3) while upregulating that of antioxidant genes (GPX4, GPX1). The results suggest NAC supports semen chilled storage in endangered species by enhancing antioxidant capacity and inhibiting cell death-related pathways. This study provides insights into the application of reproductive biotechnology in small ruminants.