Kastelic, JohnMohamed, Abdallah Mohamed Shahat2023-01-172023-01-172023-01-12Mohamed, A. M. S. (2023). Consequences of testicular heat stress and potential amelioration strategies (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/115685https://dx.doi.org/10.11575/PRISM/40603Heat stress (HS) is a worldwide problem due to temperature elevations associated with global warming. Monitoring temperature changes in testes and scrotum over time is important to understand thermoregulatory capacity of testes and scrotum. Temperature data loggers (DLs) are reliable devices that can be implanted in scrotal subcutaneous tissues to serially record intrascrotal temperature without altering animal behavior. Testicular HS causes a variety of outcomes, depending on the degree and duration of testicular heating. Some effects of testicular HS on testicular tissues, blood flow and sperm quality and attempts to prevent them, by treating animals or semen extender, have been reported. The overall objective of this study was to investigate impacts of HS on sperm quality and use various ameliorative strategies to mitigate these detrimental effects, using bull and ram models. We validated data loggers as a reliable, less invasive and serial method to measure intrascrotal temperature. Scrotal subcutaneous temperature was significantly increased by scrotal insulation or whole-body heating, but not by scrotal neck insulation; however, all three heat-stress models decreased sperm motility and morphology in bulls and rams. In addition, our hypothesis that melatonin or L-arginine improve quality of frozen-thawed sperm from HS rams was supported; 1 mM of either gave best results, except 0.5 mM minimized DNA Fragmentation Index (DFI%). Moreover, during hot weather, bulls voluntarily accessed shade, significantly lowering scrotal subcutaneous temperatures and improving sperm quality. In rams exposed to testicular HS, slow-release melatonin significantly improved testicular blood flow, protected sperm motility and morphology, and lessened HS-induced reductions in post-thaw sperm quality. Therefore, melatonin has potential for mitigating effects of testicular HS under field conditions.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Heat stressTestesSpermMelatoninL-arginineShadeVeterinary Sciencedoctoral thesis