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BEEF NUTR I T ION
WINTER 2015 ISSUE
LIVESTOCK MATTERS
8
A bacterial culprit
Bacillus licheniformis
is a bacterium found in
soil, from which it can be introduced into
silage clamps. It is the most commonly
diagnosed infectious agent that causes
abortion in cattle in Scotland.
Lee-Anne explains: ‘The Bacillus targets the
placenta causing inflammation and restricting
the blood supply to the calf; this deprives the
unborn calf of oxygen causing it distress. This
can result in the calf being aborted – between
150 and 270 days in the pregnancy.
Alternatively it can result in a stillbirth, or the
birth of a dopey calf which does not have the
energy to suckle and hence is more likely to
die early.
‘Bacillus cases are usually isolated one-offs,
and not the storm that Alan experienced. And
it was strange that none of the neighbouring
farms had experienced this problem.
‘Following a literature search, and with the
help of the SAC, a diagnostic test for the
bacterium was developed. We took samples
from Alan’s silage clamp for analysis as well
as some from a local farm which had not had
any stillbirth or abortion problems. Alan’s
silage contained more than three times the
bacterial count of his neighbour’s. And it was
present both at the silage face and deep
within the pit, indicating that the Bacillus
growth occurred during the ensiling process
rather than as a consequence of aerobic
spoilage at the face of the pit.’
Lee-Anne adds: ‘Beamwham has a reservoir.
The surrounding grass fields are also quite wet
and Canada geese graze these pastures in
the winter. Alan cuts silage from these fields,
and we found evidence in the literature that
the bacterium can harbour in bird feathers.
‘So there was a cycle of infection which
needed to be broken. The Bacillus can survive
through the cow, and so it would be present
in cow dung which was spread on the silage
fields, and then, perhaps with the added
contributions from the wild birds, be ensiled
each year.’
Solution: A ration change
With high levels of Bacillus identified in the
silage, the solution was to completely remove
grass silage from the diet of pregnant cows
and replace with a straw-based ration.
So in December 2014, Alan began feeding
his pregnant cows with ration based on straw
(wheat) and distiller’s grains.
Lee-Anne explains: ‘It was now very important
to ensure the pregnant cows were being fed
appropriately on this straw-based ration. So I
carried out some early PD tests – when cows
were expected to be between 5 and 12
weeks pregnant. Then the cows were divided
into three groups according to their body
condition and pregnancy status.’
To relieve pressure on the amount of straw
required, for the 2014/2015 winter Alan
allowed some cows to run through empty to
form a small autumn calving herd.
The calving period was also tightened up.
Alan explains: ‘Before the 2012/13 calving
season I’d been on an AI course. I keep all
my heifer replacements and so wanted to put
some different bulls onto them so I could use
my own bulls for longer. I was also concerned
that the herd was becoming very pure and I
was losing the milk yield. So I was AI-ing my
heifers with British Friesian sexed semen.
‘As I was new at this, I’d started early. But
heifers had held. So in 2012/2013 I ended
up with a calving season that started in
October instead of December!’
Alan has now adjusted his breeding strategy;
heifers are AI-ed just once, and non-pregnant
animals then put to the bull, so there is less
time lost if the AI is not successful. For 2017,
he will organise half the cows to calve in
January-February and the rest April-May.
The straw has been an unwanted additional
cost to Alan. But it is only needed for
pregnant animals. The youngstock, store
calves and replacement heifers can still be
fed grass silage.
For the 2014-2015 calving season, Alan
was extra vigilant, and primed for any
calving that looked ‘suspicious’.
The straw strategy was a success. Alan says:
‘There were no stillbirths and the few calf
deaths that occurred were not related to the
bacterium. So I’m ‘hopeful’ that the problem
has been resolved. But I don’t want to tempt
fate just yet, so I’m waiting to see how the
2016 calving goes!’
The farm’s reservoir attracts wild birds which could
be carriers of the Bacillus
A temporary autumn calving herd has been
established
Pregnant cows on straw-based ration
Going forward
Lee-Anne explains: ‘Alan is going to need
to keep feeding his pregnant cows on
straw-based rations for the next few years.
The Bacillus-contaminated muck and slurry
has been spread on arable land.’
Alan and Lee-Anne will continue to monitor
the situation. The bacterial levels in the
silage are being routinely analysed. Alan
has reseeded one of the silage fields after
ploughing under the muck, in the hope of
reducing the contamination – he is awaiting
test results to see what effect this has had.
Lee-Anne adds: ‘We needed to break the
cycle; the cows were consuming the
high-Bacillus silage, and then their slurry
was being spread onto silage fields. This
allowed infection levels to build up. So this
problem had, quite literally, been brewing
for a while.’