Artificial Insemination (AI) is the use of collected semen from bulls to inseminate and impregnate cows; without the two ever having to meet.
Without the aid of modern scientific knowledge or techniques, getting the ideal characteristics for your farm crop or animals took generations. It is done by a process known as selective breeding. It works like this...
If A Farmer wants to get cows who produce more milk, he will mate the best cows with bulls who come from a mother that produces alot of milk. In the hope of producing calves who have high milk yields. He will then carry this process on with the offspring and after many years, his cows will be producing more milk and he will be making more money!
This is a technique to try and combine all the best (most productive) genes together in one cow. Of course there isn't really an end-point to this because you are always needing to strike a balance between different things depending on the circumstances. Artifical insemination allows selective breeding to be sped up.
Collection and Storage of Semen
Bulls are trained to ejaculate (emit semen) into an artificial vagina, where the semen can be collected.
The ejaculate is analysed and can be diluted to 500 samples. Egg yolk and glycerol are used to protect the sperm cells from ice crystals.
The samples are put into 0.25ml straws that are then gradually cooled until they are stored in liquid nitrogen at -196oC (77 kelvin) and can remain as such indefinately.
The insemination must take place when the cow is ovulating, this is called Oestrus, and she displays behaviour that indicates to the farmer she is ready to be inseminated.
The straw is warmed to body temperature before use and then put into an insemination gun or catheter which is inserted into the cow's vagina and positioned past the cervix (which filters sperm) and then deposited. Ensuring the sperm arrive in time for ovulation.
The characteristics of bulls are recorded so that a farmer can select the prefered characteristics (phenotype) for his calves. Like:
It is more cost effective for the farmer, since he does not need to keep a bull for insemination himself.
There is greater flexibility, because a farmer can have a variety of calves from different fathers, bred for different traits.
Bulls can be very aggressive, so keeping them is potentially dangerous. With AI, the farmer need not keep the bull and so improves safety.
Many diseases can be passed on by sexual contact. Sperm donors have tight controls over their health, so their semen is unlikely to contain pathogens that may infect the cows.
Updated: 8 October 2012