• The bulls used for semen collection should have good pedigree.

• Bulls should have good body score and there should not be any abnormalities in the genital organs.

• Bulls must be vaccinated for the infectious diseases at right time.

• Bulls must be screened for the infectious diseases before their introduction in the breeding programme.

• Bulls must be groomed properly and they should be provided mild exercise.

• Semen from a bull should not be collected more than twice in a week.

• The semen collection should be done by a trained person so that the bull obeys the command of mounting without getting aggressive. It will also minimize the chances of injury to bull.

• The artificial vagina used for the semen collection should be clean and dry.

• The artificial vagina should be properly assembled by the tight fitting rubbers so that there is no leakage of water or air during the semen collection.

• The temperature and pressure should be maintained properly for the easy collection of semen from the bull

• The collection of semen should be nearest to the semen cryopreservation and analysing centre.

• The collected semen should be assessed for the macroscopic (volume, colour, consistency, viscosity, odour etc.) and microscopic (concentration of spermatozoa, live dead percentage, morphological abnormality, mass and progressive motility etc.) examination every time for each animal during semen collection.

• Appropriate semen extender should be prepared in advance before the semen extender and should be equilibrated for the temperature.

• The semen doses should be prepared after calculation of spermatozoa for each doses and dilution by appropriate semen volume of semen extender.

• The protocol of semen cryopreservation should be strictly followed to minimize the loss of the quality of semen.

• All the doses should be labelled properly for easy identification of the animal.

• A log book should be maintained to ensure that the semen doses sold to different centres or technicians can be traced easily, if required.

Precautions

• The semen examination should be performed by the trained person.

• It should be made sure that the inter lab and intra lab variations by the observer should within the acceptable range.

• A proper control sample should be used while examining the semen.

• It should be made sure that all the reagents used for the microscopic examination of the semen are not expired.

• Once in a period of two months, the person who does microscopic evaluation of semen should be tested again for the variation in his observation.

• Reference ranges of different parameters of semen should be strictly followed.

Semen storage in the form of straws has revolutionized the assisted reproductive technology in livestock industry. Straws allow the storage of semen in bulk quantity in the farm, artificial centre and in the storage tanks. It also allows better delivery of the semen to the female reproductive system than the ampoule. The semen straws offer advantage of uniform control of freezing and thawing process. However, semen straws are more vulnerable to the mishandling.

Semen Tank Management

Semen tank for the storage of liquid nitrogen and semen straws should meet the minimum standards and there should not be any compromise in this regard. The neck of the tank is most susceptible to the damage by sudden jarring or swinging motion leading to vacuum loss and therefore insulation lost. This leads to increased temperature in the inner container. Frost accumulation at the top of tank indicates rapid evaporation of liquid nitrogen.

Recommendations to handle semen storage tank

• Avoid excessive stress on the tank caused by excessive movement or abuse. Therefore handle the tank gently and use both hands to lift tank from handles.

• Monitor the liquid nitrogen level in the tank regularly and maintain a record of the liquid nitrogen loss as even new tanks may have defect.

• Keep semen tank away from direct sunlight but in good light and observe the tank regularly for the loss of liquid nitrogen.

• If there are some holidays, then make sure that the tank has sufficient liquid nitrogen or one may assign duty to a person to check the tank at least once in a day.

• Keep the tank elevated above the wet and poorly ventilated surfaces. Check the container for the corrosion as it adversely affects the life of tank.

• Try to store the semen straws in the AI centre needed for the six months.

Recommendations for handling semen within the tank

• Semen straws have larger surface-to-volume ratio and this makes it more susceptible to thermal fluctuation and thermal injury. Thermal injury to semen is irreversible and cannot be reversed by returning the semen straws to liquid nitrogen. Therefore to minimize the thermal injury to semen following semen handling practices should be practiced:

• Transfer of the semen straws between the containers must be rapid and carried in co-ordinated manner.

• Transfer should be carried by minimum of two peoples and keeping the tanks, filled with liquid nitrogen, side by side.

• The canisters or goblets should be raised only to the level to make the rack of semen visible.

• Keep the semen from same bull in same rack and avoid mixing of semen straws.

• Secure the goblets as low as possible while taking the semen straws out for thawing. Plunge the semen straws back to the container as soon as possible.

• In case, the semen straws cannot be removed from the goblet, bend the top tab of goblet by 45 degree angle to minimize the chance of bending the straw.

• Always wear shoes and gloves, and use tweezers to take out the straws.

Thawing of semen straws

Semen straws have high surface area and thus they are more prone to thermal injury due to the fluctuation in the temperature. Therefore, to minimize the damage due to thermal injury after taking out the semen straw from the semen storage tank, recommendations for thawing of semen straws are as

• Follow hygienic procedures during the process.

• Warm water upto 95°F and plunge the straw into that horizontally. Vertical thawing of the straw in water gives gradient temperature along the straw.

• Check the temperature of thaw water immediately before removing the straw from the tank.

• The thermometer should be accurate and easy to read.

• The duration of thaw should be at least 40 seconds.

• In some cases, semen straw thawing recommendations of the organizations supplying the semen straws should be used.