297 Evaluation of Semen Characteristics During Pubescent Maturation After Prenatally Induced Stress of Brahman Bulls

Abstract

Abstract The objective of this study was to determine if prenatal stress impacted semen characteristics during pubescent maturation of Brahman bulls (n = 23). Prenatal stress was achieved by transporting Brahman dams for 2 h on d 60, 80, 100, 120, and 140 (± 5 d) of gestation. Semen from sexually maturing males born to transported (PNS; n = 11) or non-transported (CON; n = 12) dams was classified based on motility and concentration as prepubertal (< 10% and < 50 million), peripubertal (≥ 10% or ≥ 50 million), pubertal (≥ 10% and ≥ 50 million), or sexually mature (≥ 30% or ≥ 500 million). Sperm characteristics were determined by staining sperm with specific dyes [viability - Propidium Iodide and SYBR-14; Mitochondrial membrane potential (MMP) – JC-1; DNA damage – Aracidine orange; ROS –conversion of H2DCFDA to DCF and conversion of hydroethidine to ethidium] and analysis on an Amnis FlowSight flow cytometer. Treatment differences were tested by SAS procedures. Analysis of repeated measures (PROC MIXED) and chi-square (PROC FREQ) compared semen characteristics and percent pubertal versus mature, respectively. There was a weak tendency (P = 0.14) for more control bulls to reach puberty (100%) compared with PNS bulls (82%), but no difference (P = 1.0) in percentage reaching sexual maturity by 22 months of age (82% and 82%). Scrotal circumference (P < 0.01) and motility [at collection (P < 0.01) and post-thaw (P = 0.05)] increased as bulls matured but was not impacted by treatment (P > 0.86) or treatment by time (P > 0.60). Sperm viability (at collection, post-thawing, and post-stress test) was not impacted by treatment (P > 0.20), time (P > 0.53), or treatment by time (P > 0.50). Proportion of viable sperm with high MMP was not impacted by treatment (P = 0.70) or treatment by time (P = 0.49), but was increased (P = 0.03) in early peripubertal collections compared with pubertal or mature collections. Proportion of sperm with damaged DNA was decreased in PNS (1.6 ± 0.3%; P = 0.04) versus CON (2.4 ± 0.2%) but not impacted by time (P = 0.47) or treatment by time (P = 0.41). Percentage of sperm with elevated ROS (H2O2 and •O2) was not impacted by treatment (P > 0.33), time (P > 0.17), or treatment by time (P > 0.41). Prenatal stress tended to impact the proportion of bulls that reached puberty but had no impact on the percentage that reached sexual maturity by 22 months of age. Prenatal stress also impacted the proportion of sperm with DNA damage, but did not impact scrotal circumference, motility, MMP, or ROS. Stage of sexual maturity impacted scrotal circumference, motility, and MMP, but did not impact ROS. In summary, PNS may impact the ability to reach puberty, but did not impact sperm characteristics from prepuberty to sexual maturity.