Association between levels of insulin-like growth factor-1 in serum and seminal plasma with fresh and frozen-thawed semen characteristics in Beetal bucks

The aim of this study was to investigate the relationship between the levels of insulin-like growth factor-1 (IGF-1) in serum and seminal plasma and the characteristics of semen in Beetal bucks (Capra hircus). A total of 12 adult Beetal bucks were involved in the study, with each buck providing six ejaculates collected using a standard artificial vagina (n = 72 total). Only qualified semen samples (volume of 0.7 mL, a mass motility rating of 3+ or higher on a 0-+ scale, and individual progressive motility of 80% or more) divided into three fractions were processed for estimation of IGF-1 and other seminal parameters like motility, viability, acrosome integrity, sperm abnormality and superoxide dismutase (SOD) activity. The first and second fraction were diluted and extended with Optixcell extender (1:15 ratio). The first ejaculate fraction was processed for studying fresh semen parameters and the second fraction was cryopreserved for evaluating frozen semen parameters. French mini straws (0.25 mL) were used for semen filling, and polyvinyl alcohol powder of different colours was used for sealing the extended semen. The third fraction of each ejaculate was centrifuged at room temperature (1100 x g for 7 min) to separate the seminal plasma. Additionally, blood samples were taken from each buck on the same day as semen collection, resulting in a total of 36 blood samples. The results revealed a significant positive correlation (r = .4243; p < .05) between the concentration of IGF-1 in both serum and seminal plasma of the Beetal bucks. Furthermore, the concentration of IGF-1 in serum showed significant positive correlations with sperm viability (r = .554; p < .05), acrosome integrity (r = .527; p < .05), post-thaw sperm motility (r = .407; p < .01), post-thaw sperm viability (r = .426; p < .01) and post-thaw acrosome integrity (r = .333; p < .05). However, it had a significant negative correlation with SOD activity in fresh semen (r = -0.458; p < .01). Moreover, the concentration of IGF-1 in seminal plasma demonstrated significant positive correlations with individual progressive motility (r = .341; p < .05), sperm viability (r = .527; p < .05), acrosome integrity (r = .539; p < .05), sperm plasma membrane integrity (r = .464; p < .05), post-thaw sperm motility (r = .644; p < .01), post-thaw sperm viability (r = .643; p < .01), post-thaw acrosome integrity (r = .487; p < .01) and post-thaw sperm plasma membrane integrity (r = .521; p < .01). Additionally, it showed a significant negative correlation with SOD activity in both fresh semen (r = -0.714; p < .01) and frozen semen (r = -0.558; p < .01) of Beetal bucks. Based on these findings, IGF-1 in seminal plasma can be considered as a potential biomarker for the selection of bucks for breeding purposes.