How to prevent sulfa residues in hogs
Since the 1950’5, sulfa
compounds have been used
m rations fed to swine to help
control such diseases as
atrophic rhinitis,
pneumonia, and dysentery.
These sulfa compounds,
especially when used m
combination with an
tibiotics, have also been used
extensively in starter and
grower rations to prbmote
growth.
Research shows that use of
antibiotics in combination
with sulfa m starter rations
for young pigs can increase
growth rate as much as 21
percent and feed efficiency
as much as 8 percent (versus
nonmedicated rations).
An estimated 70 to 80
percent of all hogs marketed
m this country receive some
form of sulfa during their
lifetime.
One unfortunate
byproduct of the widespread
use of sulfa has been
violative residue levels in
some carcasses. The
tolerance for sulfa in pork -
designed to provide a 2,000-
fold safety margm for
humans - is 0.1 parts per
million.
During 1978 and earlier
years, some 10 to 15 percent
of the hogs tested at
slaughter by the U.S.
Department of Agriculture
were in violation of this
tolerance level.
A hog doesn’t have to eat
very much sulfa to have a
violative level in its carcass.
As little as a quarter
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teaspoon of sulfa con
tamination m a ton of feed -
about 1 ppm - could produce
a violative level.
Medicated feed contains
100 grams of sulfa per ton of
feed or 110 ppm. Carryover
of medicated feed in augers,
mixers, storage bins, and
other feed handling equip
ment can easily contaminate
finished feed. As little as 20
pounds of medicated feed
will contaminate 1 ton of
finishing feed.
Research has shown that
sulfamethazine - the most
commonly used sulfa drug -
is cleared from a hog’s
tissues within 7 to 10 days
when a nonmedicated feed is
fed. Currently, a 15-day
withdrawal period is
required when
sulfamethazine is used in the
feed.
Sulfathiazole, the only
other sulfa drug approved
for use m feed, has a 7-day
withdrawal period.
However, because of the
pervasive nature of sulfa
compounds, stringent
quality control measures are
needed at the feed mill and
farm to prevent con
tamination of nonmedicated
feed.
Many farmers who turned
up with violative levels of
sulfa in their market hogs
believed they were feeding a
sulfa-free withdrawal ration.
However, tests of feed and
feed components showed
sulfa contamination.
A recent USDA survey of
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violative, producers showed
that nearly 35 percent of
supposedly nonmedicated
finishing feed had
sulfonamide levels high
enough to cause residue
problems in slaughter swine.
Sulfonamides are elec
trostatic and cling to metal.
So contamination can and
will occur in feeders,
mixers, wagons, etc., where
medicated feed has
previously been handled.
Hogs can also pick up
residues from manure and
unne from other hogs being
fed sulfa.
As part of a residue
monitoring program, USDA
meat inspectors randomly
check hog carcasses in
slaughtering plants for
residues of sulfa and other
drugs and pesticides and
other chemicals.
When violative levels of
sulfa are found, the producer
is notified by a USDA
representative and is ad
vised that to ship hogs to
slaughter m the future, he
must choose between two
methods:
—Send hogs to market and
have carcasses retained at
the slaughter plant until they
are tested and found below
tolerance. (It often is very
difficult to find a packer who
will hold carcasses for the
necessary 2 weeks for the
USDA testing to be com
pleted.)
—Send a sample lot of five
hogs to slaughter for “pre
market” testing. The
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producer must then wait for
i weeks or more to be
notified of USDA test results.
If the test hogs are free of
sulfa, the balance of his hogs
can be sent to slaughter.
Either choice disrupts
normal production and
marketing operations.
How Can Farmers Avoid
Sulfa Residues?
When buying fmishmg
withdrawal feed and/or feed
components, ask the sup
plier for assurance that it
will not produce violative
sulfa residues. Keep feed
samples with code or lot
numbers so tests can be
made if the hog marketed
have violative levels of sulfa
residues.
CLEAN all storage areas.
This includes bulk feed
storage bins as well as areas
where bagged feed is stored.
This is particularly im
portant if the bm or area was
previously used to store
medicated feed. If possible,
never use a bulk bm for both
medicated and non
medicated feeds.
CLEAN all feeding
equipment. This includes
feed wagons and mixer
grmders, as well as the
feeders themselves. Scrape
clean all areas of the feeders
to eliminate feed buildup on
wood or metal parts. If
possible, flush feeders with a
high-pressure hose before
putting m nonmedicated
finishing feed.
Make sure no feed has
collected inside augers and
mixers. Check all cleanout
ports on mixer-grinders.
Use a large shop vacuum
cleaner to remove residual
feed in processing and
conveying equipment. These
“tailings” can be used in the
next batch of medicated
feed. Remember,
sulfonamides are elec
trostatic and cling to metal.
CLEAN watering systems
if they have been dispensing
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sulfa. With metal pipes, it’s
extremely difficult -
sometimes impossible - to
get nd of sulfa con
tamination. Do not use
lagoon water to flush feeders
or finishing feed floors.
CLEAN contaminated
manure from finishing pens
when switching to a sulfa
free finishing ration...and
again 3 days later, since
sulfa in the manure pack will
continue to be recycled
through hogs.
Follow label directions.
Read the labels carefully
and completely on all feeds.
Use sulfa drugs m swine
rations according to
manufacturers’ directions.
Mix feed correctly. Make
one person responsible for
adding medicated premixes
and other concentrates to the
feed. Establish a mixing
order for all ingredients.
Follow mixing instructions
to the letter. Don’t overload
the mixing capacities of your
equipment. Premix all
concentrated medications
into large enough quantities
of ingredients - such as com
or soybean oil meal - to
assure accurate mixing of
the medicated feed.
Flush mixing equipment.
After mixing mediated feed,
run several hundred pounds
of cracked or ground gram
through the equipment.
Remove flush materials
from mixing equipment and
store separately for future
use m medicated feed.
Withdraw sulfa at least 15
days before hogs are
marketed... Preferably, sul
fa medicated feeds should
not be used' after market
swine reach 100-125 pounds -
it’s just not economical.
Get advice from your
veterinarian if you must feed
sulfa after 125 pounds
because of a disease
problem. Then try to use a
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