Boron Protects Sperm Functional Attributes During Cryopreservation of Bull Semen

The impact of boron on reproductive health of the mammals remains unexplored. This study investigated protective effect of boron in semen extender during cryopreservation. Fresh semen samples from Jersey bulls (n = 8) were collected using artificial vagina and diluted in tris-based extender (80 million sperm /ml). The diluted semen samples were divided into four analyte groups: control and three boron-adjuvated groups (0, 0.3, 0.45, and 0.6 µg of boric acid/100 µl of semen extender, respectively) and cryopreserved in liquid nitrogen. After one week of storage, the cryopreserved semen samples were thawed at 37 °C for 30 s and subjected to sperm kinematics, viability, acrosome integrity and functional membrane integrity, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and nuclear chromatin decondensation analysis. Boron at 0.45 µg/100 µl in semen extender significantly protected sperm total motility (p < 0.01) and MMP (p < 0.05) as compared to control group. The ROS level increased significantly at higher doses of boron (0.45 and 0.6 µg/100 µl) compared to the control group. The straightness, linearity, and oscillation indices (%) along with functional membrane integrity (%) reduced significantly at the highest dose (0.6 µg/100 µl of extender). Furthermore, addition of boron favored the ability of sperm (%) undergoing nuclear chromatin decondensation (p < 0.05). The study suggests that 0.45 µg boron/100 µl of semen extender preserves bull sperm motility and MMP. However, the increase in ROS may be attributed to enhanced mitochondrial activity in sperm. Further investigation on field fertility is needed to conclude the potential effect of boron as an additive in semen.