All the advantages of artificial breeding can be lost with decreased conception rates by improper handling of frozen semen and insemination short cuts.
Semen is most frequently damaged during handling after thawing and prior to inseminating the cow. The following practices may help to reduce losses incurred from low CR's due to improper semen handling and AI procedures.
Items needed to successfully perform AB, include the AI gun, plastic sheaths, gloves, paper towels, tweezers, lubricant, thawing thermos all of which should be kept clean and dry. If soaps and disinfectants are used for cleaning they should be thoroughly removed since chemicals are lethal to semen.
Time spent removing semen straws from the liquid nitrogen tank must be kept to a minimum to reduce semen damage.
Temperatures can reach 12oC in the neck of the tank and repeated exposure of batches of semen above the frost line can seriously damage semen quality.
"The greatest damage to semen occurs when too much time is taken to locate semen".
It is a major problem which can be reduced by:
There are various recommendations, however thawing semen between temps of 32-35oC for 40 seconds allows more semen to survive the thawing out process. Never thaw the semen in your pocket or the cow – this reduces the number of viable sperm cells. The straw should be completely dried with clean paper towel since dirt and water are lethal to semen. Use clean dry equipment to handle semen.
When inseminating a number of cows, several straws can be thawed out at once in a proper thermos flask. The amount of semen thawed out should not exceed the quantity that can be inseminated in 10-15 minutes. Never refreeze partly thawed out semen.
Facilities have an impact on insemination effectiveness particularly if large numbers of stock have to be artificially bred. Attention needs to be given to secure gates, unnecessary obstructions, shade, reduced noise and a crush that works well.
"Minimal stress to stock and operators improves AB effectiveness and conception rates".
With large numbers of inseminations repetitive strain injury in the shoulder can be minimised by technique (see later).
All equipment (gun, tweezers, scissors etc.) must be free of dust, dirt and chemicals. With chilly weather the gun should be pre-warmed to avoid "cold temperature shock". The loaded semen gun should also be protected from the sun.
Loading of multiple AI guns (4-5) can be detrimental to conception rates particularly if considerable time is taken with each insemination.
It is suggested that the cow is inseminated as soon as possible after thawing the semen.
An important factor influencing pregnancy rates is the quality of semen.
"The use of low quality semen increases the number of inseminations and reduces conception rates".
Sometimes high quality semen may give disappointing conception rates. This probably suggests that our present knowledge of semen technology is not perfectly correlated with post insemination characteristics which influence fertilisation rates.
Breeding records can help identify semen which gives below average results.
Simple rule – only those persons who have been adequately trained and have sufficient practice should inseminate your cows. Untrained personnel quickly become fatigued and the accuracy of semen deposition is reduced.
AI is a skill that should not be compromised, this includes:
Cows that are not mated at the correct stage of the heat cycle have reduced conception rates and extended calving intervals. Follow the "am and pm" thumb-rule but remember that this is simply a guideline. (Diag. 4).
Acknowledgments: Information and advice provided by Dan Jillella and Phil Chamberlain, Veterinary Consultants, Brisbane.