الفهرس 
Cover Page Title in EnglishOnly 14 pages are availabe for public view
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Abstract
The use of AI, based on frozen-thawed semen, can greatly increase the number of offspring produced per sire per year because one ram has the potential to produce enough spermatozoa to inseminate thousands of ewes. Although, semen collection in farm animals is not a sterile procedure, and some degree of microbial contamination cannot be avoided. So, the aims of the present study were; to investigate possible relationships between the presence of fungal contamination in the ram ejaculate with the freezeability of processed spermatozoa, to study the effect of addition of antimycotic drugs to semen diluents on the quality of yeast contaminated frozen-thawed semen and finally to select an optimum antimycotic agent(s) to be added to cryodiluents of sheep frozen semen.Semen samples were collected from 6 Barki rams and processed for cryopreservation after adding different concentrations of griseofulvin, clotrimazole, nystatin, fluconazole or amphotricin-b to semen diluent. Sensitivity of Candida albicans and Cryptococcus neoformans to antimycotic drugs were studied. The diluted semen samples were experimentally contaminated by Candida albicans and Cryptococcus neoformans making of their frequent isolation as cited in titrationsfollowed by recording of the isolation rate of viable yeasts in cold stored and frozen thawed ram semen. Also, the effects of yeasts and antimycotic drugs on sperm cell motility and viability were studied. Results showed that:Fluconazole and nystatin (at dose not higher than 50 mg/l) had no deleterious effect on sheep semen freezability. Rather it was attracting that fluconazole had improving effect to sperms especially at concentration of 12.5 mg/l. Higher doses of amphotricin-b and griseofulvin resulted in drastic deterioration of frozen semen quality. While clotrimazole showed a moderate effect. Candida albicans and Cryptococcus neoformans were in vitro sensitive to fluconazole and amphotricin-b and resistant to lower concentrations of griseofulvin and clotrimazole.The experimental contamination of ram semen with Candida albicans and Cryptococcus neoformans (table 3) resulted in a dose-dependent reduction in post-thaw motility. - Using lower doses (0.5 mg/l) of Candida albicans and Cryptococcus neoformans resulted in non-significant reduction in post-thaw motility (55.00 ± 4.08 and 55.63 ± 2.13%, respectively) and in viability index (149.00 ± 4.83 and 156.06 ± 7.85, respectively) as compared with those of the control group (58.63 ± 0.63% and 157.56 ± 8.47, respectively). The post-thaw motility and viability index of semen contaminated by the higher dose of Candida albicans (40.00 ± 2.04% and 101.00 ± 7.11, respectively) were significantly (P ≤ 0.01) lower than those of Cryptococcus neoformans (47.50 ± 3.32% and 121.63 ± 13.12, respectively), and both of them were significantly (P ≤ 0.01) lower than those of the control non-contaminated semen samples (58.63 ± 0.63% and 157.56 ± 8.47, respectively).rHead-to-head agglutination of spermatozoa in semen contaminated by the higher dose of Candida albicans was the main cause of drastic reduction of spermatozoal motility.It was noticed that a significant number of cells of the inoculated Cryptococcus neoformans and Candida albicans survived cryopreservation with a survival rate up to 30.00 and 22.34%, respectively.Candida albicans and Cryptococcus neoformans were highly sensitive (both in vitro and in vivo) to fluconazole at a final concentration of 50 mg/l.There was dose-dependent reduction of the post-thaw motility and viability index of sheep spermatozoa with the increment of the dose of all the tested yeasts and antimycotic drugs.Conclusively, addition of fluconazole to sheep semen diluent has a benefit of improving the quality of yeast contaminated sperm with no bad effect on the frozen-thawed semen quality. It is recommended that, since it is both desirable and technically feasible to prevent contamination during the collection and processing of bovine semen, it is recommended that acceptable commercial preparations of extended semen should be completely free from yeasts. Moreover it prevents the possibility of concentration of semen with yeasts that may exist as flora or infection in the vagina and further transmit it to cause probable infection to either the mother or embryos.