Semen Collection from Bulls
A large majority of dairy cows in the US, Canada and European countries are artificially
inseminated. Artificial insemination of beef cows is also popular, particularly in purebred
herds. The advantage of AI over natural service is that it facilitates rapid genetic
improvement by allowing use of only the top bulls. Some bulls have sired more than
100,000 offspring via AI.
Semen is most commonly collected from bulls in bull studs using an artificial vagina, as
described below. Electroejaculation is an alternative method used with bulls that cannot
mount or are too fractious for easy handling (e.g. range bulls). Finally, semen can be
collected by message of the seminal vesicles and ampullae per rectum.
Semen Collection via Artificial Vagina
Semen collection from bulls using an AV requires three people: one to handle the teaser
animal, one to control the bull and one to collect the semen. It is important that the
collection area have non-slip flooring to avoid injuries and because ejaculation may be
inhibited if the bull is nervous about his footing. Bulls are heavy and should have regular
hoof care. Poor hoof condition can inhibit the bull from mounting or cause pain when
dismounting.
A steer is most commonly used as a teaser
and mount animal. Female teasers are not
recommended because of the potential risk
of intromission and spreading of venereal
disease. The teaser should be a calm
animal of the appropriate size for the bull
being collected.
The back and rear quarters of the teaser are washed with a disinfectant every collection
day. It is also common for the rear quarters to be clipped routinely. The bull's preputial hair
should be clipped in preparation for using the AV. These sanitary precautions are intended
to minimize microbial contamination of the semen being collected.
For collection, the teaser is positioned straight in front of the bull for mounting. Oftentimes,
it helps to arouse the bull if the steer is led around the collection arena with the bull behind,
then stopped abruptly, similar to the behavior of a cow in estrus.
The artificial vaginal (pictured at right) uses thermal and mechanical
stimulation to stimulate ejaculation. The liner of the AV is filled with water at
42-48 degrees Celsius, and the inner surface is lubricated with something
like K-Y jelly. An insulating cone is placed over the end from which the
collection tube protrudes to avoid subjecting the semen to temperature
shock.
False mounting is an effective way to sexually stimulate the bull. Providing
two false mounts with two minutes of active restraint and one additional
false mount maximizes sperm cell numbers. Final preparations are made to
the AV between the second and third false mounts. Proper construction of
the AV is important to avoid damaging the bull's penis and to avoid stressing
sperm cells.
Successful semen collection with an AV depends on the bull being
comfortable around people, and they need to be trained to use the AV.
However, bulls are big and dangerous, and personnel safety should be
emphasized constantly. Most bulls in artificial insemination centers have a
nose ring installed as a valuable and humane means of physical control.
Bulls undergoing semen collection should be haltered and one should never tie a bull up by
their nose ring - if startled, then can rip it out which is not only quite traumatic but yields an
animal that may be exceptionally difficult to control. During collection, the person handling
the AV must remain aware of where their feet are relative to the bull. As the animal
ejaculates, it is common for him to jump forward. To avoid foot injury, collectors should
wear boots with steel toes.
In artificial insemination centers, bulls are typically collected 2 or 3 times per week, with 2
or 3 ejaculates per collection day. The following images depict routine semen collection
from a bull.
False mounting to arouse bull
An erect penis indicates arousal
Collector ready with AV
Collector diverting penis to the AV