A good injection technique will ensure valuable carcass cuts are not damaged and reduce the risks of injury to those involved in giving the injection and the animal itself.
When injections are performed poorly it often leads to an abscess or scar tissue, causing the most valuable cuts to be condemned.
Abscesses develop when an injection is administered incorrectly or with a dirty needle.
In some cases they can lead to the loss of the whole carcass, warns Alison Small, a specialist in Veterinary Public Health based in Bristol.
When meat inspectors find an abscess or active inflammation consistent with an injection having been given, they may recommend investigation for residues of vet medicines,” she says.
“This is expensive and often by the time the investigation is complete the carcass is so old it cannot be used for meat.
So, even when it is found to be safe from a medicines point of view, it is disposed of at the expense of the producer.”
Oriel Jones’ abattoir in Llanybydder slaughters 28,000 lambs a week and although there have been significant reductions in levels of condemned carcasses in recent years, the problem still occurs.
“Some abscesses or growths can be cut off, but sometimes you can lose a whole leg and that really reduces the price,” says managing director Paul Edwards.
“As the retail and export markets account for a big proportion of our business, we are unable to sell a carcass when part of it is missing.
They have to go for cutting.”
Older animals including cull ewes, cows, sows and boars show more incidences of abscesses and injection scars than young, slaughter-generation animals.
A major cause of scarring in cattle is copper supplementation.
Small abscesses are often found behind the shoulder.
“This is where the irritant copper injection has entered the grazed muscle, rather than being administered truly subcutaneously,” says Miss Small.
So how can farmers minimise risk of tissue damage?
Vet Steve Borsberry regards adequate restraint as a key factor.
“In my opinion, you shouldn’t inject adult dairy cows in the parlour.
“When they are climbing up from the pit it is easy to get wrong.
A crush or a race should be used.”
This is as much for the safety of the farmer as the animal, suggests Mr Borsberry, of the 608 Vet Group, Solihull.
“When a farmer injects himself with an oil-based vaccine it’s not a case of visiting an accident and emergency department, but going straight to a consultant surgeon,” he says.
“It can cause intense vascular spasm which can result in the loss of a digit.
Prompt surgery is necessary to flush out the tendon sheaths.”
Sterile needles are also essential, he stresses.
Needles should never be re-used because this increases the risk of infection and, as the needle becomes blunt, it can damage tissue giving rise to abscesses.
A dirty needle, or a clean needle passing through dirty skin, can bring infection into the injection site.
This infection attacks the body cells, killing them faster than the macrophages — specialist clean-up cells — can clean them up.
Equally, a large volume of medicine can also result in abscesses because it causes pressure inside the tissue and kills body cells.
When too many are killed, the body can’t cope and an abscess forms.
Fresh needles should be stored in a locked cupboard and used needles kept in a special “sharps” container which can be supplied by a vet.
BEST INJECTION SITES FOR CATTLE AND SHEEP
Subcutaneous injections should be applied behind the shoulder of cattle and sheep.
This area is recommended because there is no likelihood of pressure necrosis, which leads to abscess formation.
A flap of skin on the neck could be pulled up, but is more difficult to access, particularly with cattle in a crush, says Miss Small.
The nature of this injection means it must be applied under the skin.
For intramuscular injections, Miss Small recommends the muscle of the neck.
“Turn the head away from the handler, so muscle can be felt on the curve of the neck, and inject deep into it.
“Aim for about midway between the crest and the bottom of the neck, about half-way along the neck.
“When you aim too low, where the neck folds around the windpipe, there is a risk of injecting into the vein which could kill the animal or damage important nerves.”
Although the rump is a good accessible area to inject, injecting here leads to scarring and possible abscess formation, spoiling a valuable cut of meat.
AREAS TO AVOID
Never try to inject into the bone, or right next to the bone, warns Miss Small, as this can cause severe tissue damage.
Also, the medicine will not be so readily absorbed.
“Vets sometimes inject anaesthetic into the gaps between the vertebrae, before doing abdominal surgery, but never think of copying that site,” she says.
“There are many important nerves near the spine and the sirloin is the most valuable cut of meat.”
Only people with specific training should inject into the main body of an animal.
For pigs, the hind leg area is best avoided because this is where the most valuable cuts of meat are.
The neck is the ideal area, but it is important to properly restrain the animal because there is a possibility of a needle breaking off in the neck.
This not only risks an abscess forming but the presence of a needle in the meat may not be noticed until the meat is prepared for retail sale.
“The needle may also work its way out of the pig and fall onto the floor, then sick into the foot of another pig or a stockman, causing a nasty injury.”