PLEASE ANSWER THE FOLLOWING QUESTIONS

More documents

Recommendations

Info

Benha University Faculty of Veterinary Medicine Department of Theriogenology Model Answer Time allowed: Three hours 5th Year Exam (Artificial Insemination and Embryo transfer-2011/2012) Date: Thursday, June 14, 2012 Total Marks (50) PLEASE ANSWER THE FOLLOWING QUESTIONS 1. Good quality semen is essential to have good extended semen: a- Mention the principles characterizing the good semen extender in a bull? (5 marks). Answer: Characters of good semen extender: The essential properties of a good diluter are: 1- Osmotic pressure. - If the tonicity of the medium deviates considerably, spermatozoa may have bent tails, swim in circles, and die. - Extenders developed to preserve sperm should ideally be isotonic under the conditions used, and thus should not cause morphological or functional damage. - Solutions that are similar in composition to body fluids or are naturally produced liquids, such as egg yolk and milk; appear to be compatible with sperm. 2- Buffering capacity: Spermatozoa require protection from metabolic by-products, primarily lactic acid, especially when they are stored without refrigeration. Buffering solutions protect sperm cells from even minute changes in pH due to lactic acid formation. 3- Protect sperm cells against cold shock. - To protect spermatozoa against the effect of chilling, lecithin, proteins, lipoproteins and similar complexes found in Egg yolk or milk will be provided 4- Protect sperm cells against freeze kill. It is necessary to added antifreeze kill e.g. glycerol to semen to protect it during freezing and thawing. Glycerol binds water decreases the freezing point of solution. Less ice is formed in its presence at any temperature. The level of glycerol varies somewhat with the extender ingredients. Yolk-citrate, whole milk, and Tris-buffered-yolk should contain 7%. Skim milk extender performs better with 10% glycerol. 5- Control bacterial growth and/or contamination - Some organisms usually will be found in semen from healthy bulls even under aseptic semen collection and processing conditions. It is therefore standard practice to include antibiotics such as penicillin and streptomycin in all extenders used commercially.
- Penicillin (1,000 IU/ml) and streptomycin (1,000µg/ml) were used to control both pathogenic and non-pathogenic bacteria in semen and reduce sperm metabolism as well. - The antibiotic polymyxin B was reported to increase fertility of frozen semen but failed to demonstrate an improvement when added to extenders containing both penicillin and streptomycin. - Clindamycin and tylosin were effective against several mycoplasma and ureaplasma isolates of bovine origin 6-Provide nutrients. Spermatozoa, requiring energy for motility, are capable of both aerobic and anaerobic metabolism. Semen extenders should supply a simple energy source such as glucose or fructose in order to protect the intracellular reserves of spermatozoa as well as cell components. Fructose is available in seminal plasma, while egg yolk contains some glucose and other compounds utilizable by bull spermatozoa Some examples of nutrients used in semen extenders: 1. Egg yolk (most common) 2. Milk 3. Coconut milk 4. Reconstituted dried buttermilk 7- Protect cellular enzymes. Extenders should contain substances that protect against the increase in the metabolic activity e.g. CO2 and organic acids (Caproic acid) and consequently maintain sperm viability, livability and metabolic activity. 8- Free from toxic substances and/or bacterial products. - Not only should extenders be formulated to prevent the formation of toxic products during storage, but should be free of substances that are harmful to spermatozoa. - Heavy metals are harmful to spermatozoa, proper distillation of water insures that only nontoxic trace amounts remains. - Only pure reagents shouod be used in formulating buffer. - Dead spermatozoa are a source of amino acid oxidase which is harmful to surviving cells through the production of H2O2. 9- Cheap and easy to be prepared. 10- Maintain the life span of sperm with minimal drop of fertility. ****************************************************************************** b- How to prepare an extender suitable for semen storage at 5 o C (5 marks) Answer: a) Egg yolk based extenders: Egg yolk phosphate extender ◦ Phosphate buffer-----------80ml Sod. Dibasic phosphate 2.0g Pot. Dihydrogen phosphate 0.2g
Page 1: Benha University Faculty of Veterin
Page 5 and 6: 4. Keep the prepared extender in wa
Page 7 and 8: c) Cumulus cell expansion observed
Page 9 and 10: Penetration of the sperm into the o

PLEASE ANSWER THE FOLLOWING QUESTIONS

Create successful ePaper yourself

Delete template?

Save as template?