الفهرس 
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Abstract
This work has been carried out at the International Livestock Management Training Center (LIMTC) Sakha Kafr El-Sheikh Governorate and National Institute of Laser Enhanced Science (NILES) Cairo, University.During the last years, studies have monitored a high alert of low fertility males, which appear in a decrease of the semen quality and quantity that affects the productive system leading to decreased productivity The interest in the animal production field to produce a high percentage of meat and milk quantity and preserves livestock species, to overcome problems such as insurance against global climate change, disease threats, social changes, and other unforeseen disasters. The reasons for the fertility decrease are unknown until now, but many studies have suggested that the reason may be external factors from the surrounding environment, such as short electromagnetic waves, many types of Nanoparticles. These factors effects must be studied under different conditions like long times light exposure, dose, and the interactions between the biological cells with different elements In this thesis, we studied improving bull semen quality given two factors; the first one is using laser light with specific wavelengths (632.8 nm and 532 nm) to enhance the quality of bull sperms with decreasing the photochemical effect on molecular changes in sperm DNA. The second one is adding different concentrations of chitosan Nanoparticles to bull semen before the treatment with the selected laser wavelengths (632.8 and 532 nm) to investigate their effects on decreasing the photochemical effects on the sperm quality and the changes on bull sperms DNA. The obtained results showed a definite influence on the DNA after exposure to laser wavelengths for periods exceeding 6 minutes. Therefore, we added chitosan nanoparticles to study their suitability for preserving the gene expression, which led to allowing a more extended exposure period for the laser while protecting the genetic material. These results can be used to improve the quality of semen storage for more extended periods and to preserve the DNA from damage. It also indicates the importance of using chitosan nanoparticles during the process of purifying the semen extender media. Besides, the same technique can also be used in genetic improvement processes and the production of strains with genetic characteristics that have economic feasibility in the field of animal production policy of the country.