RESIDUE AVOIDANCE PROGRAM-INJECTION TECHNIQUES FOR SWINE
Prepared by H. Neil Becker, clinical veterinarian, University of Florida;
Richard Taylor, practitioner, Fayette, Mo.; Maynard Hogberg, head, Animal
Science Department, Michigan State University; and James McKean, extension
veterinarian, Iowa State University. Edited by Gene R Hettel, communications
specialist-- agriculture, Iowa State University,
Modern health practices in swine production
require numerous injections or "shots." These injections provide pigs with
iron compounds, antibiotics, vaccines, bacterins, hormones, anti-inflammatory
drugs, vitamins, anesthetics, and replacement fluid products.
Routes of Administration
Every product has a specific and approved
route[s] of administration that gives maximum results with minimum problems.
Recommended routes are specified on the label. Read the label carefully
if you have any questions about the route of administration, amounts to
be used, or other precautions.
There are four routes of administration:
 subcutaneous [SQ], just below or beneath the skin;  intramuscular
[IM], into a muscle;  intraperitoneal [IP], within the abdominal
cavity; and  intravenous [IV].
This route of administration is often
used in baby pigs still nursing the sow. A readily available site with
loose skin is just inside the flank along the abdominal wall [figures 1-4].
Restraining the pig is easy. When held
up by its back leg, the injection site will be exposed inside the rear
leg. Using this site avoids damage to muscles and nerves. To avoid leakage
from the injection site, slide the needle under the skin away from the
site of skin puncture before depositing the drug. A major advantage of
SQ administration is that relatively large quantities of drug, fluids,
etc., can be given under the skin without fear of causing pressure damage.
This is the most commonly recommended
injection site. Drugs given IM are generally absorbed into the blood faster
than with SQ administration. To avoid leakage from the injection site,
pull the skin forward slightly before inserting the needle. After the needle
is inserted, release the skin, give the injection, and remove the needle.
The skin will spring back into place, covering the hole in the muscle and
sealing the injected material in the animal.
In young pigs, much damage can occur
if injections are not done properly. Depositing irritating drugs near the
sciatic nerve which runs next to the bone in the rear leg may result in
lameness and, in some cases, loss of the leg. Selecting clean sites for
injections will reduce chances of abscesses. If abscesses form when injections
are given into the ham or other muscles, they may destroy a valuable cut
of meat. Therefore, the neck area is the preferred site of injection in
all pigs [figures 5-7]. Injections should be given directly behind the
ear on the side of the neck. Care must be taken not to inject the drug
into fat because then the drugs will be poorly absorbed.
Needle length is dictated by the age
of the animal. Although a 1/2-inch needle is appropriate for IM injection
in baby pigs, it is totally unsatisfactory for heavy sows. The amount of
fluid that can be safely given in a muscle is also dictated by size. In
baby pigs, 1 to 2 cc/site is enough. In sows, volumes of 5 to 10 cc/site
may be given. If more must be given, divide the dosage into several locations.
High dosages at one site can cause pressure damage to the muscles and retard
When giving IM injections, it is a
good idea to draw back on the syringe after the needle is in the animal
to make sure that the needle is not in a blood vessel. Some drugs, such
as Procaine Penicillin G, can be fatal if injected directly into a blood
vessel instead of a muscle.
This route of administration is generally
avoided because several complications may occur. Abdominal organs may be
punctured by the needle and injection of irritating drugs may cause peritonitis.
Also, adhesions of organs to the abdominal wall or to each other may lead
to reproductive problems later in life. IP injections should be given only
with veterinary guidance and instruction.
There are not many superficial veins
that can be found easily in swine. Ear veins are the preferred site, but
are difficult to hit. Therefore, this method is not used routinely. It
is the most common route for anesthetic agent administration because the
drug is rapidly transported to the sites of action.
Factors Affecting the Injection Technique
Several factors affect the particular
method used for giving injections. These include:  age and size
of pig,  restraint method,  product to be injected,
 volume of the product to be injected,  viscosity or
flow characteristics of the product, and  required administration
Small pigs are easily restrained and
good restraint makes any injection easier. Because the muscles are smaller
in young pigs, care must be taken to ensure proper IM injections. Larger
pigs [greater than 50 pounds] and adult sows and boars are more difficult
to restrain, but the potential injection sites are also larger.
The approved route of administration
must be followed to avoid illegal residues. The volume and viscosity of
the product influence the injection site and the selection of needle length
and gauge [diameter]. Needle size is designated by its gauge and its length
the higher the gauge number, the smaller the diameter of the needle. IM
injections will usually require longer needles than SQ injections. When
a product is very viscous or thick, common sense dictates choosing a large-diameter
needle. However, select the smallest diameter practical [the largest gauge
possible] which will allow rapid administration. This will minimize damage
to the pig and cause less stress. Also, a smaller hole will reduce drug
leakage from the injection site.
Injection Needle Selection
Many injection needle gauges (diameters]
and lengths are available. In general, use the needle having the shortest
shaft and the largest gauge [the smallest diameter] possible. As length
increases, decrease the gauge to give added shaft strength which will reduce
bent or broken needles.
Two general types of injection needles
are available--reusable stainless steel [figure 8] and disposable nonironbased
[figure 9]. Stainless steel needles are stronger than disposable needles,
but are initially more expensive. With care, they can be reused many times.
When the needle point becomes dull, it may be resharpened. Reusable needles
may be more economical per injection than disposable needles.
Disposable needles are cheaper initially,
but break more easily and cannot be resharpened. Very few pork producers
change needles between each pig, so the advantage of being disposable is
minimal except when there is a chance of spreading disease, For example,
in herds where eperythrozoonosis is a known problem, it is important to
change needles between each pig to prevent the spread of this blood-borne
Table 1. Millimeter Equivalents for Inches.
Needle lengths are still measured in
inches, but with the impending change to the metric system, table 1 shows
the metric equivalents.
Syringe Selection and Care
Several different types of syringes
are available. Selecting the proper syringe will ensure a proper injection
technique and minimize injection problems.
Disposable [plastic] syringes.
There are many sources of disposable
syringes available, but with few exceptions, these syringes are similar
in construction. The main differences are in the type of tip where the
needle attaches. A tip located off center is intended primarily for IV
injections. The two main types of tips are Leur slip and Leur lock [figure
10]. The slip type is designed so that the needle hub may be slipped onto
the tip. Except for use in piglets, the lock-type syringe hub is preferred
because it has the strongest attachment [figure 11]. The slip tip is easily
bent and broken if animal movement occurs at the time of the injection
Nondisposable (reusable) syringes.
These syringes usually are made of
combinations of glass, metal, plastic. and ceramic parts. The so-called
automatic, or pistol grip multiple-dose syringe is the most popular style
[figure 13]. Even though several different types of automatic syringes
are available they are similar in action. These syringes have a dose adjusting
mechanism that may be set for a 1- to 5-cc delivery with every squeeze
of the trigger. This type of syringe requires constant maintenance because
of its many moving parts, but offers the advantages of quick dose delivery
and a preset volume adjustment. It is very convenient and time saving to
have the dose volume preset, particularly when injecting large numbers
of similar age pigs.
Plastic disposable syringes may be
cleaned and reused several times. Take particular care in cleaning and
disinfecting automatic syringes. The best way to clean these is to disassemble
the barrel and plunger and to wash them in warm, soapy water. After thorough
cleaning, disinfect the parts and then rinse several times with clear,
clean water to remove any traces of the disinfectant. This is particularly
important if modified-live vaccines are used in the syringe because residual
disinfectants could kill the vaccine components and render them ineffective.
Boiling the syringe parts in water is another good way to disinfect. Take
care not to overheat the plastic and rubber parts.
Store the cleaned syringe disassembled
or assembled. If stored assembled, apply a small amount of light oil or
glycerine to the rubber plunger to keep it lubricated and prevent it from
sticking to the glass barrel. Provide a clean, dust-free storage place.
Do not store a clean and disinfected syringe on a dirty shelf in the hog
Most producers will give injections
with the needle already attached to the syringe. However, certain situations
may require placing the needle into the animal and then attaching the syringe.
To do this more easily, use the slip type of syringe tip.
When using an automatic syringe with
the needle attached, follow these steps:
1. Restrain the animal securely.
2. Select proper dosage on the syringe.
3. Locate the injection site, clean the site, and disinfect with alcohol,
iodine, or other suitable disinfectant.
4. Make sure no air bubbles are present in the syringe.
5. Quickly and firmly insert needle into the animal.
6. Quickly deliver material (squeeze the trigger].
7. Keep the trigger depressed while removing the syringe and needle.
8. Release the syringe trigger and prepare for next injection.
Occasionally inspect the syringe and
dose-setting to ensure that nothing is broken or has changed.
Problems Associated with Injections
Failure to deliver the proper dose.
This may result because of animal movement
(improper restraint]. Very few injectable materials work when applied on
the pig; they must be injected into the pig! lf the syringe is broken or
not adjusted properly, too little or too much product may be injected.
Also, be very careful not to inject yourself or your assistant. Serious
injuries and infections have resulted from misdirected injections into
the hands, arms, and legs of people.
Just like people, individual pigs may
be very sensitive to certain drugs. Read the product label, be aware of
the potential problems, and be prepared to deal with them. Epinephrine,
antihistamines, and cortisones should be a part of the medicine supply
maintained by pork producers for their animals. Check with your veterinarian
for information about how, when, and in what manner to use them.
Swelling and/or abscessation at the injection site.
Certain injectable products are more
likely than others to cause swelling and/or abscesses at the injection
site. Minimize these problems by cleaning the injection site. Do not inject
areas that are wet and dirty. When using multiple-dose bottles, leave a
needle in the vial and use another needle for administration. This reduces
potential for contamination of the vial with a dirty needle and is particularly
important for injectable iron preparations. If there is a choice, use products
that are the least irritating.
Broken needle shafts.
Several pork processors have had products
returned by irate customers who have found broken needle shafts in the
meat. Most of these shafts were from disposable-type needles. You can avoid
most of these problems by using proper stainless steel needles and good
restraint. Broken needle parts in the sausage, bologna, or lunch meat do
nothing for the excellent image of pork products.
The injection of concentrated drug
solutions results in high drug levels at the entry site. Absorption may
be affected by the total amount of drug injected at one site or by the
tissue rejection that results. Take care to follow the label instructions
for quantities injected in one site and for site selection. Failure to
follow these directions can lead to prolonged drug levels in the tissues
and drug residues. ln addition, mark pigs and keep records to avoid marketing
pigs before proper withdrawal periods have expired. Read the label to obtain
the proper information.