Sheep Farm Husbandry - Injection Techniques

Animal health, disease prevention, injections, methods, techniques, hygiene, safety.

By Dr Clive Dalton & Dr Marjorie Orr


General - hygiene

• When giving injections always get veterinary advice to make sure the products are appropriate and you know the correct procedure. A loaded syringe can be a dangerous weapon for both you and any helpers. If anyone does get injected, then seek immediate medical help and take the product with you to the doctor.
• Keep your tetanus vaccinations up to date too.
• Follow the manufacturer’s instructions to the letter for storage and use of the product.
• Make sure you take care to dispose of old syringes, needles and packaging in a safe place. Needles are especially dangerous and should really go into a special “sharps” rubbish container.
• Various pathogenic bacteria are present on the surface of the skin and these may produce infection if injected with the medication.
• Therefore; when time allows or for valuable animals, or if the environment is very dirty, take every care to clean and disinfect the skin before injecting.
  
• If the injection is made on the side of the neck and the site is covered by wool, close clipping of the skin is ideal, but careful separation of the fleece and scrubbing the skin with a disinfectant may be possible.
• There are lots of disinfection preparations on the market which are satisfactory. Tincture of iodine is satisfactory and is better than methylated spirits which though commonly used, is not effective as a disinfectant.
• A fresh swab of disinfectant should be used for each animal.
• Single syringes are mainly disposable these days but if a multiple-injection gun is used it must be disinfected when practical.
• The gun, including all parts coming in contact with the drug or the product to be injected, should be placed in a large container such as a pressure cooker or saucepan and thoroughly boiled with the lid on.
• Bringing to the boil will kill all normal bacteria and boiling for 15 minutes will ensure the destruction of most bacterial spores.
• After boiling, the saucepan or container should be tipped sideways with the lid on so that the water drains out (like pouring off potatoes).
• With all the water out, the syringe and the plunger may be picked up by external parts only and carefully fitted together without touching any part which will contact the material injected. Wash and dry your hands before picking up and assembling the injection equipment.
• Equipment that cannot be boiled cannot be adequately disinfected. The best you can do is to soak it in a solution of disinfectant. Pour this off and then flush with cold boiled water. The latter should have been boiled in a lidded container and allowed to cool with the lid on.
• If they are not washed through thoroughly with water, injecting guns and syringes may contain some of the disinfectant, and this may inactivate the vaccine, or cause irritation and damage of the tissues when injected.
• To remove vaccine or other medication from the bottle in a clean manner, swab the neck and stopper of the bottle with a solution of suitable disinfectant. If sealed with a rubber or plastic seal, the material may be withdrawn using a syringe and two needles (one needle to allow air in as the vaccine is sucked out).
  
• On large farms, the above comments may be hopelessly impractical. For example, if you have to vaccinate 500 ewes with 5-in-one vaccine, you will not have time to disinfect the skin of each sheep.
  
• You may simply proceed down the race injecting each sheep in a clean part of the neck, taking care to keep your hands clean (and washing them if they become dirty), and taking care to keep the needle clean (and replacing it if it becomes dirty).
• Generally, use the smallest needle that is suitable, i.e. the needle with the narrowest bore, such as a 19-gauge needle. In tough-skinned animals a stouter needle may be necessary, e.g. a 16-gauge.
  

Subcutaneous injection (under the skin)

• This is the easiest and quickest form of injection, and it is used for many vaccines and drugs that are non-irritant and are readily absorbed.
• With stock held in a race to give a subcutaneous injection, pull up a handful of skin to make a “tent” and slide the needle into the base of the tent under the skin and press the plunger.
• Check when doing this to make sure the jet from the syringe is not coming out the other side of the tent because you’ve pushed the needle too far through.
• With irritant materials as some vaccines can be, a reaction may result producing a lump. This may blemish the carcase when the animal is killed and dressed. In such cases, make the injection at the top and to one side of the neck. Any lump that occurs here can be trimmed off when the carcase is dressed.
  

Intramuscular injection (into the muscle)

• Many drugs have to be injected deep into the muscles to give more rapid absorption and may lead to less irritation.
• Where possible the intramuscular injection should be given deep into the muscles of the neck rather than into the big muscle mass of a hind quarter. The reason is that the rear end is where the top-priced meat is on the carcass, and is the last place you want to cause an abscess in the carcase to be found when the sheep is killed or worse still – not found until it reaches the consumer!
• When injecting into the neck the sheep can see you coming and often moves, whereas injecting in the rump there is less chance of it being aware of what is going on till afterwards. If the sheep feels pain with the initial jab or when the product is being forced down the syringe, watch for the sheep moving and the needle coming out.
• It is important that the injection is not put into subcutaneous fat and actually hits muscle. That’s why it needs to go in deep.
• Just before pressing the syringe plunger; withdraw it a little and if has inadvertently gone into a blood vessel, blood will show in the barrel of the syringe. If this happens the needle must be moved to a new site so that the injection is intramuscular and not intravenous.
• If a spore of some Clostridial organism such as tetanus, blackleg, black disease or malignant oedema, is lying harmlessly in the muscle, the disturbance created by the injection may cause it to germinate leading to fatal disease. This is a good reason for keeping Clostridial vaccinations up-to-date.

Intravenous injection (into the vein)

• Avoid giving intravenous injections (into the vein) and leave them to your veterinarian as finding a vein and injecting into to it can be tricky, especially on a sheep with long wool.
• You can do intravenous injections under veterinary supervision and where you will have to demonstrate to your veterinarian that you are competent to carry out the task.
• Intravenous injections are generally given into the jugular vein in the neck and it can be tricky to find. The sheep should be well restrained when locating the vein and when injecting.
• f the vein is missed, there can be serious bleeding under the skin, and accidental injection of many medications around the vein instead of into it can cause a very nasty reaction, sometimes with sloughing of the skin.
• There are many medications that could kill or do serious damage if injected into a vein and run in too quickly.
• For example, when injecting calcium solutions intravenously, a veterinarian may listen to the heartbeat to gauge the rate of injection by the response of the heart. Without this, sudden deaths may occur.
• For large volumes e.g. for milk fever or grass staggers, injections come in bottles or sachets with a long rubber tube attached to the needle so that the solution is gravity fed and the rate must be controlled by the height at which you hold the container.
• Because the rapid injection of any medication into a vein can be lethal, all intravenous injections are given very slowly. The sheep must also be well restrained.
  

Intramammary injection (into the udder)

• In sheep, antibiotics for mastitis are normally given intramuscularly but you may need to give an Intramammary injection to get antibiotics into the udder via the teat canal.
• These are really “infusions” using the long neck on the tube rather than a needle to deliver the treatment.
• Remember the teat sphincter muscle that opens into the teat canal are very delicate structures and the teat is a very sensitive part of the sheep so work gently and with care.
• A sheep’s teat canal is much smaller and more delicate than that of a cow.
• After the full tube has been emptied into the teat, it’s no longer recommended to hold the teat end and massage the product up into the udder.
• It is also important to clean the end of the teat with meths before you insert the tube. Use cotton wool swabs and keep using them until they show no more dirt from the teat end. This may take quite a few rubs. If you don’t clean the teat end - all you’ll do is to push dirt and bugs into the teat and cause more problems.

Filling a syringe

• If you have to draw liquid from a new bottle of product into a syringe, it’s often hard to suck out because there is no air in the new bottle or container.
• All you need do is to draw into the syringe the amount of air that will be replaced by the injection, and inject this air into the bottle through the rubber cap.
• This will put enough air into the bottle and allow you to fill the syringe.
• You may have to do this every now and again if you find it hard to fill the syringe.
• Or you can put another needle in the cap of the container to act as an air entry while you are drawing product out.
• Try to keep everything as clean as possible and free from contamination.
  

Disclaimer
This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.