Cows show a number of signs when they are
on heat. The best sign is when they stand still
to be serviced by a bull or to be inseminated.
A clear mucus discharge often flows from
the vulva. Ovulation (when the follicle erupts
releasing the ovum) takes place about 12
hours after the end of the standing heat. This
is when AI should take place.
Artificial insemination is the deposition of live
semen at the correct time and place inside
the genital tract of dairy cows for conception.
Afterward the uterus can be massaged to
stimulate the movement of the semen inside
the uterus horn. Keep the cow separate and
quiet for a short time after insemination.
While AI is regarded as a simple technique,
inseminators require training to use the
correct technique. This technique should
be followed for each cow. Insemination
success varies between inseminators as often
short-cuts are tried. Although inseminator
performance is monitored about 6 weeks
later, it should be ongoing to ensure positive
results.
How to select sires
Milk production starts after calving. Getting
cows pregnant is therefore one of the most
important management actions on a dairy
farm. Two outcomes result when cows
conceive: (i) the possibility of a next lactation
or milk production period and (ii) fixing the
genetic merit of the progeny.
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Selecting sires for AI is part of the breeding
process on a dairy farm. Breeding is a
deliberate process to improve a herd, or
specific traits. Genetic improvement occurs
when better performing parents than the
current cows in the herd are selected. As
cows are already in the herd, bulls selected
to inseminate cows, determines herd genetic
improvement.
Sire selection has a long term effect on the
genetic merit of a dairy herd. The production
performance of the daughters of sires selected
today is observed only four years later. The
present commercial dairy herd consists of
cows born 3-8 years ago.
A breeding objective for a dairy herd should
aim at the products which are produced. As a
dairy herd produces primarily milk, it therefore
makes sense to select bulls that have a
high genetic merit for milk yield. This would
increase the possibility for high producing
daughters. However, selection of sires for a
single trait like milk yield is not recommended
today as a number of traits affect the lifetime
economic performance of cows. The aim is
to breed for cows that produce the most milk
from the available feeds while the milk should
have high fat and protein percentages. Cows
should also have long productive lifetimes.
Semen for AI can be bought from local or
international established AI companies. Bull
guides contain a large amount of genetic
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