Evaluation of stressors as potential indicators of male fertility

Overall objective of this thesis was to determine if the ability of individual bulls' sperm within a breed to withstand stress could be correlated with fertility. Specific objectives included 1) examine variation among individual bulls' sperm within breed to withstand stress of aging for extended time periods; 2) investigate the effects of a moderate (41.0°C) or more severe (45.0°C) elevated temperature on sperm motility overtime; 3) examine variation of individual bulls' sperm within a breed to withstand stress of elevated temperature of 43.0°C for 3 h post-thaw; 4) and determine whether ability of individual bulls' sperm within the Holstein breed to withstand elevated temperature is correlated with fertility. For sperm motility assessments, sperm were diluted 1:20 in Sperm-TALP containing 6.0 mg/ml BSA, 1.0 mM sodium pyruvate, 50 U/ml of penicillin, and 50 µg/ml of streptomycin. For in vitro fertilization, sperm were exposed to elevated temperature before fertilization of oocytes. On d 3 and 8 (d 0 = day of fertilization), ability of putative zygotes (PZ) to cleave and develop to blastocyst, respectively, was determined. Results demonstrated variation among individual bulls' sperm within breed to withstand stress of aging or elevated temperature for extended time periods. However, sperm from high fertility bulls resulted in similar embryo development as sperm from bulls of lower fertility. Surprisingly, motility of frozen-thawed bovine sperm within an AI straw can persist for as long as 15 h post-thaw, which is a greater duration than previously proposed.