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Selective dry cow therapy

by
01 June 2015, at 12:00am

PETER EDMONDSON discusses the use of selective dry cow therapy, which is intended to reduce antibiotic use and the likelihood of resistance, and calls on the profession to be proactive in this approach

SELECTIVE dry cow therapy
is where only individual animals
receive antibiotic dry cow therapy
at the end of lactation and this
selection is based on individual cow
data.

It is intended to reduce antibiotic use
and reduce the likelihood of antibiotic
resistance. It
is now being
promoted
by many
of the UK
milk buyers
and forms
part of the
guidelines
for Arla producers, where all farmers
will have to take steps to move towards
selective dry cow therapy.

Remember that dry cow therapy was
introduced specifically to help eliminate
subclinical infection at dry off. Over
the years this was amended by adding
in some Gram-negative cover to try to
help prevent new infections occurring.

There can be no justification to
administer dry cow antibiotic into a
cow that is free of subclinical infection
or that did not have a case of clinical
mastitis in any quarter during lactation.
If you look at milk records, you see
that the proportion of cows with cell
counts of over 200 is very small.

Trial work has shown that cows that
are free from subclinical infection and
are given antibiotic dry cow therapy
in conjunction with a teat sealant will
have a 12-fold increased risk of E. coli
mastitis compared to a cow just treated
with a teat sealant.

Selective dry cow therapy has been
successfully used in many countries
for many years. There is nothing to
fear provided the correct guidelines are
followed.

You need individual cell count data
and accurate clinical mastitis records
for decision-making on which cows
should get antibiotics at dry off. Some
herds don’t have individual cow cell
count data but this should not be used
as an excuse to continue with blanket
dry cow therapy. Responsible use of
antibiotics has to be based on sound
science and not economics or the
convenience of decision making.

Not every herd will be able to use
selective dry cow therapy. Herds with
high cell counts will still have to use
blanket antibiotic dry cow therapy.
These problem herds should be taking
steps to reduce their cell counts, which
offer more opportunities for vets. The
median cell count of herds in the UK
runs at below 180 at present, indicating
the levels of subclinical mastitis are
low.

Some herds will make their own
guidelines, which can prove disastrous.
Many years ago we had a client who
decided to go down the selective dry
cow therapy route without consulting
us and his cell count increased from
150 to 350 over a period of 12 months.

He thought that a teat seal also
contained antibiotics! It is very
important that farmers work with their
vets to ensure that sensible and sound
decisions are made.

Some considerations to help decide
if selective dry cow therapy is suitable
at a herd level:

  1. Is the herd cell count under 200?
    If over 200, steps should be taken to
    reduce the herd cell count and blanket
    dry cow therapy used until this occurs.
  2. Do less than 25% of cows have
    cell counts over 200? If above 25%
    this suggests widespread infection
    and there is a greater risk of missing
    infected animals.
  3. Does the herd have a significant
    Staph. aureus problem? If so, use
    blanket dry cow therapy until this is
    resolved. It can be very difficult to
    identify all Staph. aureus cows.
  4. Is Strep. agalactiae present? If
    present, blanket dry cow therapy is
    recommended in the short term until
    levels have been significantly reduced.
  5. Are there low levels of Strep. uberis
    infection? If high, this would indicate
    that there will be many cows that have
    clinical and subclinical infections.
  6. Are individual cell count records
    available? If not, testing of individual
    animals should be started. This does
    not mean that they have to be tested
    monthly. Samples could be collected
    for the last three months before dry
    off.
  7. Are there accurate clinical mastitis
    records? There should be as it is a legal
    obligation. If not, the farmer should
    start to record all of these immediately.

Once you have established that
the herd is suitable for selective dry
cow therapy it is important to agree
guidelines with your clients. This will
be on a farm-by-farm basis using their
history to make sound decisions.

There are a range of guidelines
depending on which country or
website you look at. In Ireland, the
recommendation is to treat if any cell
count was over 200 in the last three
tests of lactation. In New Zealand, the
recommendations for heifers are to
have cell counts under 120 throughout
lactation and under 150 for dairy cows.

All recommend that you use dry cow therapy in the quarter that had
clinical mastitis. This is because cure
rates for the Gram-positive cases are
low and it is important to clear up
any residual infection.

You will always miss some cows
with subclinical mastitis as any cell
count test result is made up of milk
from four quarters. A cow with a
SCC of 150 might have individual
quarter results of 30, 40, 50 and
600, where this high quarter has
subclinical infection. However, this
needs to be put into context, as
the proportion of infected cows
is relatively low. The risk decreases
when the percentage of cows with
cell counts over 200 is low.

A cow that does not receive
antibiotics at dry off should be given
an internal teat sealant to minimise
any risk of mastitis in the following
lactation. In fact, every cow that is
dried off will benefit from internal
teat sealants. These reduce the
levels of clinical mastitis in the next
lactation by between 25 and 30%
and offer an excellent return on
investment where the farmer clearly
sees the benefits.

All of the above shows that there
is significant opportunity for vets to
work with their dairy clients and guide
them through the selective dry cow
therapy maze. This is important from
the outset but also on a continuing
basis to ensure that correct decisions
are being followed and that there are
no adverse effects on mastitis.

It is down to the profession to be
proactive in this approach to selective
dry cow therapy.

  • The next Mastitis Control and
    Quality Milk Production Seminar
    run by Peter Edmondson and Roger
    Blowey will be held from 8th to 10th
    November. See www.sheptonvet.com
    for more details.