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One other winter forage that has become a
very popular feed lately is fodder beet. This
also can cause the problems mentioned
above but additionally the roots are extremely
high sugar and low fibre, leaving animals at
an even higher risk of acidosis and milk
fever. Oxalates are also present in fodder
beet; these bind calcium in the gut. This
means that whilst feeding fodder beet cows
are susceptible to milk fever even before
they calve.
One important job at the end of lactation
that we as vets get involved with is assessing
trace element statuses. Trace element
supplementation of grazing animals in
New Zealand has produced marked
improvements in productivity of sheep, beef
and dairy cattle. However they cannot be
given indiscriminately as this may result in
death of the animal and/or unacceptable
levels in the livers and kidneys for human
consumption. The patterns of deficiency are
pretty unpredictable across Canterbury and
where soil types are the same, differences
can still occur. So each year as they
approach dry off most farms sample a
selection of animals to see where their
levels are.
22 'essential' trace elements or minerals are
required by cows but the main ones we are
concerned with in New Zealand are copper,
selenium, cobalt, iodine and occasionally
zinc, manganese and chromium. As soil
levels are poorly correlated with the mineral
content of forages the most accurate
assessment of mineral status is done by
taking liver biopsies and blood samples.
The liver is much more accurate for assessing
copper levels than blood. This is because
when copper intake is below requirements,
the animal will use its liver store to maintain
its blood level within the normal range, so
blood levels can appear normal even when
the liver copper is severely depleted. Usually
we select about 6 cows, with this number
biopsies can be done in about an hour
and a half in a rotary parlour. Liver biopsy
is relatively uncomplicated and is the most
accurate way of sampling for trace elements.
Some people get liver samples tested from
cull cows at the abattoir however normally
we don't recommend this as culls often do
not fully represent the true status of the herd.
If a herd is deficient in one of the trace
elements it may be supplemented
accordingly. There are several different
oral and injectable products on the market.
Many people here use dosetron injectors
which supply the minerals in measured
amounts through the drinking water.
This is also an important time of year for
mastitis control. This is because cows with
infections have a higher chance of being
cured in the dry period than in lactation.
It is also a crucial time with regard to
preventing new infections occurring in the
next lactation. As you can imagine when
farmers are drying off a thousand cows over
two or three days it can be very tempting
to take short cuts with dry cow therapy.
However, as you are probably aware,
injecting dry cow tubes up dirty teats can
cause a lot more problems later on or even
cause mastitis during the dry period.
A relatively new practice in New Zealand is
using teat seal on heifers from about 4-6
weeks before calving. Data from New
Zealand farms show that heifers here have
the highest age-specific incidence of clinical
mastitis of all cows, with the largest majority
of cases being diagnosed in the first 2-3
weeks of lactation. Most cases are caused
by Strep. uberis. Studies have shown that
using teat seal in heifers reduces clinical
mastitis so much that any herds that have an
incidence of heifer mastitis over 13% should
see a cost benefit. As such many have taken
up using teat seal. You might be surprised to
hear we manage to do this in both rotaries
and herringbones with hardly ever getting
kicked. Most seem so surprised at their
surroundings the first time they come in they
stand stock still! The hardest part usually is
bringing them into the parlour, especially if
they are not used to being handled. Obviously
it is absolutely crucial the teats are fully clean
and sterilised as the potential for introducing a
bug would be very high otherwise and the
consequences disastrous. But despite it being
a tricky job the benefit is very obvious and
almost everyone who has done it once
before did it again this year.
The other big news over here is that in the
last month new rules have come out
regarding inductions. As I said in my last
article, inductions are used over here in order
to tighten calving patterns and reduce cow
wastage. However, with growing concern
about the welfare of this, new targets and
an operational plan have been set. By 2012
the maximum level of inductions undertaken
in individual herds will be dropped from
15% to 4%. This is different to previous
targets because they are now set at an
individual farm level rather than a national
level. For some of our herds, especially the
large ones which have relied on inductions,
this will mean changes will have to be made
with regard to managing the calving spread
and it will be interesting to see how different
farms manage this.
Long term the aim is inductions will be
phased out altogether as their negative
image is seen as a substantial risk to the
industry over here.
AUTUMN 2010 ISSUE
LIVESTOCK MATTERS
24
Taking a liver biopsy