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For many years
we have tested bulls’ fertility with an artificial
vagina, but this requires the presence of a female animal in heat,
is time consuming and poses a risk to those who handle the bull.
Consequently, the service has not been used very often.
Keeping a defective
bull or ram can be a costly business. Figures from the SAC show
that the average cost of keeping a bull is about £1000
per year. Large studies into bull and ram fertility have shown
that about three in ten are defective.
Infertile bulls and rams are rare, but in 2004 we found two infertile
bulls in two small suckler herds. At one PD session none of the
twenty-five cows presented were pregnant, and at the other only
two out of thirty females were pregnant. In both instances it was
too late to turn a new bull out to get the animals calving in the
spring/summer.
It can be very difficult to identify an infertile bull, particularly
on farms where several bulls are kept and there is no accurate
recording of which animals have been running with which bull at
what time, but finding a sub-fertile bull or ram can be even more
of a challenge.
A sub-fertile bull or ram will get some animals pregnant, but
it will take several services and therefore more time. As most
people calve their animals only in the spring or the autumn, the
consequence of a sub-fertile bull is more empty females at the
end of the breeding season. A sub-fertile bull will also lead to
a spread out calving pattern. This is not only a nuisance, as pregnant
animals need to be checked longer (which has an impact on labour
costs), but it will also lead to a variation in the age of the
calves, which will have an impact on calf health. Calf scour pathogens,
for instance, need time to build up. Therefore, calf scour is normally
a problem at the end of the calving season, but the longer the
calving season, the worse the problems. A variation in calf ages
can also result in an increased risk of pneumonia as older calves
carry and spread pathogens to which they are immune to younger
and more susceptible animals.
Therefore, sub-fertile bulls and rams are just as much of a nuisance
as infertile bulls and rams. They cost money and create a health
risk, and should therefore be identified.
The Electroejaculator:
Since late
2004, we have been using an electroejaculator to test bulls’ semen. It is a sophisticated version of the one we
use to test rams with. Unlike the old ram probe, the new electroejaculator
stimulates more accurately the internal male sex glands and has
less effect on the nerves of the hind legs. We have bought a special
ram probe as well so we can now also test rams with it. As bulls
can be tested in a crush, it is a very safe (for human and animal),
quick and easy way to test a bull’s fertility.
The Procedure:
When the bull is entering the crush, his gait inspected. His feet
are inspected when in the crush. He gets a full clinical examination
of external and internal sexual organs and the size of the testicles
is measured. This reflects directly on the quantity of the semen.
After manual stimulation of the internal sexual organs, a probe
is inserted and gentle electro-stimulation is applied until ejaculation.
The
semen is scored for volume, concentration and contamination before
being examined under a microscope. All this takes place
on-farm. Under the microscope, the sample is examined for gross
motility and motility of individual sperm cells. A sample of the
sperm cells is stained and back at the surgery the morphology of
100 sperm cells will be examined.
Our
Initial Findings: Semen is extremely sensitive to cold shock. Consequently semen
testing cannot be done in poor weather conditions because it could
lead to poor semen motility and tertiary abnormalities of morphology
(high numbers of loose heads and bent tails).
As most of
our progressive beef suckler clients have had their bulls tested
and we have tested the first few sweeper bulls in
dairies, we have examined over seventy bulls already. We have seen
a range of abnormalities: scrotal hernia, testicular deformation,
small testicles, “broken penis” and, of course, reduced
ability to mate due to lameness. The semen showed: contamination
with urine and pus(!), deformed sperm cells (a wide variation),
but the most common abnormality of semen was poor motility, ie:
less than 30% of sperm cells with a forward progression.
Most, if not all, bulls were re-tested before a negative advice
was given. The bulls that were condemned ranged in age from eighteen
months to twelve years. Some were after a pre or post sale check,
others had been on the farm for many years. Some bulls were tested
following poor PD results, but by far the most were routine tests.
It has become
clear that an annual bull fertility check can be very beneficial,
as bulls can become sub-fertile at a later age.
Most farms spend a lot of time and money checking their cows’ fertility,
so why not also pay attention to their bulls’ fertility,
which is equally vital? |
