If castrating cattle with a knife and covering with penicillin, we always observe the pen for two things – excessive bleeding and any telltale signs of an allergic reaction.
Since allergic reactions in cattle are rare, they are not mentioned much in the literature. But today’s producers are giving more vaccines and antimicrobials, and with longer-acting products that are only approved subcutaneously or intramuscularly and not intravenously, the risk is higher.
The carrier or base in the products also can cause allergic reactions, so you never know when one will arise, but the treatment is very effective if given in time.
Most allergic reactions come about from the administration of products such as vaccines or antibiotics. Less commonly, an allergen can be inhaled or taken in orally. The reaction may be local, such as with a bee sting where the tissue in a large surrounding area becomes swollen. With cattle, we are more concerned with the full-blown reaction where eventually the lungs can fill with fluid, resulting in death.
Most severe reactions usually happen within 15 to 20 minutes of the insult. Clinical signs might include uneasiness or increased respiration. The most noticeable signs can be swollen, puffy eyelids and copious salivation. Bloat and staggering often follow these signs, which can progress to collapse from the lack of oxygen. The animal turns blue and dies.
A good routine is to take a quick look at cattle once they have settled after processing to observe anything abnormal. If castrating cattle with a knife and covering with penicillin, we always observe the pen for two things – excessive bleeding and any telltale signs of an allergic reaction. My experience with antibiotics is that if you get one reaction, there may be several. There can be a genetic susceptibility in a herd to a specific allergen, so if you inject a number of animals and you get one reaction, watch very closely for others. Mark down the animal affected especially if it’s a breeding animal as it could reoccur next time. That product needs to be avoided on that animal.
Have treatment ready
In producers’ treatment kits there should always be a bottle of epinephrine, the universal antidote for allergic reactions. If you never need to use it that is a good thing. The bottle will often get dust covered and expired, so check once in a while and replace it as necessary. Allergic reactions happen quickly and it will be too late to go to the neighbour’s or rush to the veterinary clinic to purchase a bottle. Even if you have an expired bottle it can be used in a pinch and may save the life of the animal. Efficacy may be decreased and you may need to use more to get the desired results. The one good thing about allergic reactions is you know right away if the treatment is working.
Dosage of epinephrine is one cc per 100 pounds given subcutaneously or intramuscularly (the product comes in the strength of one mg per ml). One may want to hurry the process by giving it intravenously but that can cause heart fibrillation. If given this way it is diluted to a 10 per cent solution with saline and only one-quarter of the dose given. I personally don’t recommend it. If the animal is having difficulty breathing it is fractious, so best to give it quicker by the other routes described. I have a tendency to split the dose in two places giving one subcutaneously, the other intramuscularly. Clinical signs will begin to decrease within minutes.
You are not done yet as often the dosage may need to be repeated several times as the epinephrine wears off so keep the affected ones under close observation. You want at least an hour after the last treatment before being fully confident the allergic response will not return. Corticosteroids such as dexamethasone may also be prescribed for longer coverage.
Notify the vet
Do all this in consultation with your veterinarian. It is good if he/she is aware of any allergic reactions as several steps may be taken. Often if a product is involved the pharmaceutical manufacturer wants to know and check the product. You may be advised not to use the product if there is thought to be genetic susceptibility.
Individual reactions can occur with some products if not approved for intravenous usage and you happen to hit a small arteriole when injecting. This likelihood has been dramatically reduced with most products now approved subcutaneously. If given properly subcutaneously it is almost impossible to hit a big enough vein or artery. For intramuscular products like daily penicillin it is a good preventive to first place the needle and then attach the syringe with the product. If blood comes bubbling out of the needle it is best to pull it out and place it in another location. I always tell farmers I could induce an allergic reaction every time by giving penicillin intravenously.
Our management practices have reduced many individual allergic reactions. Pharmaceutical companies also monitor which carriers and immune stimulators cause more reactions and try and develop effective but less reactive ones. Hopefully you will never have an allergic reaction on your farm, but if you do have epinephrine on hand and labelled. It is cheap insurance and most definitely could save several lives.
Roy Lewis is a large animal veterinarian practising at the Westlock Veterinary Centre. His main interests are bovine reproduction and herd health.