There are various toxicity tests that determine how effective a product is and how to safely use it.
There is an acronym called LD 50 (for lethal dose), which is the concentration or amount of a product to kill 50 per cent of the patients. Fortunately, most cattle products we use are very safe. But that is not a reason to overdose. Calibrating doses is part of the licensing process. Moreover, if we exceed the dosage, then the withdrawal will be increased as well.
So, sticking to the recommended dose on the label is paramount. And more is not better as it costs more money as well.
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It’s also important that we recognize the products that have a smaller margin of safety.
One is a very specific product to treat cryptosporidiosis called Halocur (there’s also at least one generic version). Crypto is the protozoan disease that often causes unresolved diarrhea in younger calves. Halocur is a very specific, almost preventive treatment, for it.
The label even warns about giving it to calves that are sick, although I would still treat calves because the risk is outweighed by the good it will do. The big ‘but’ here is that if you double the dose, even in healthier calves, it will make them sick.
This is why it’s critical to know weights, especially for young calves. We often assume most newborns are 100 pounds but some are considerably lighter than that.
The biggest mistakes I have seen in dosage are giving newborn lambs the calf dose of selenium. By weight this is about a tenfold overdose and will result in toxicity. With young small calves and lambs, get an actual weight and determine the right dosage for that weight.
The cost of medications has led producers to follow the dosage closely under the guidance of their veterinarian. Longer-acting products have a slower release component or the blood levels are above the necessary amount to inhibit or kill the bacteria for the length of treatment time indicated.
Dosage can vary considerably from product to product so read the label carefully. Where possible, put up dosage charts in the processing area as a reminder and also to help train new employees. When jumping back and forth, it is easy to forget, so do not be afraid to look up dosages.
Some pharma companies will supply laminated dosage charts or they may be on protective bottle covers or as fridge magnets. I wish more companies would clearly put dosage and withdrawal on the bottle, so it is easy to find. Statements such as ‘read the dosage on the insert’ are pet peeves of mine. Spreadsheets are available with a list of products, their dosages and meat withdrawal times, so search these out.
Your veterinarian can definitely provide advice on using products for conditions that aren’t on the label.
Companies cannot put on the label all of the conditions for which their antimicrobials are effective. The respiratory pathogens as well as common things like foot rot, pinkeye and other major bacteria-causing pathogens may be on label but not any of the minor ones.
The route of administration is another thing to pay attention to.
We all know that while Micotil (tilmicosin) is a good antibiotic for pneumonia, there is a huge safety concern if accidentally given intravenously. This is a real worry when producers have used it a lot in dart guns.
I hope veterinarians are not recommending it this way and, again, one must really watch out for an accidental injection. Try to avoid any needle pricks by using the one-handed subcutaneous technique. With some products, the process can be very irritating but most times the swelling and pain one encounters is caused by the larger-gauged needles.
If a product is formulated IM (intramuscular), there is a reason. With oil-based vaccines it is often because there will be lots of swelling when used SC (subcutaneous). With other products such as the prostaglandins (estrumate), it is because it breaks down quickly so it can’t be in fat where absorption is slow.
There are also two warnings on prostaglandins. One is to make sure clostridial disease vaccines are up to date. That is because the bruising that prostaglandins cause can set up the ideal environment for clostridial growth.
The other is that prostaglandins can cause a major issue with uterine contractions that can affect females (human), so women of child bearing age should let somebody else on the team inject the prostaglandins if using it to abort heifers or set up synchronization programs.
A few products, such as sodium iodide for things like wooden tongue or lumpy jaw, have to be injected intravenously or there is trouble. This would also happen with injectable butazone (only used on horses) because severe swelling and irritation occur if not injected into the bloodstream.
For vaccines, stay away from stacking gram-negative organism treatments such as for E. coli, foot rot, pasteurella and pinkeye because cattle (calves especially) can be put into endotoxic shock. There is also the risk of modified live vaccines such as IBR inducing the disease and causing abortions in susceptible animals. It was once said over half of IBR abortions are vaccine induced, so one must be very careful.
The bottom line here is pay attention to labels, have drug dosage charts available and stick to the proper dosage and route of administration all the time.
