YC.com: Needle Selection

Vaccinating your cattle is an important step in livestock health. No matter if you own one cow or one thousand, vaccinating cattle properly is the responsibility of all cattle owners. But poor needle selection can nullify the benefits of vaccines or even lead to other problems.

Some problems are a safety issue. If a needle breaks off during an injection, it can stay in the muscle tissue. If a meat processor finds a needle fragment, it costs time and money to remove that cut of meat before it reaches the food supply.

Often broken needles are the result of an animal jumping in the chute as the injection is being administered. Proper restraint of that animal is key, and needle selection can also play a very large role.

"A smaller needle is much more likely to break," says Dr. Todd Thrift, Assistant Professor of Animal Science, University of Florida. "Because of that, I don't recommend using 20 gauge needles. 18 gauge are also prone to bend if the animal jumps in the chute." As a general rule, Thrift recommends a 16 gauge needle for most subcutaneous and intramuscular (IM) injections. "They are harder to bend."

Thrift also cautions against straightening bent needles. "Straightening a needle weakens it even more, increasing the odds it will break. If a needle bends, throw it away," he says.
Broken needles should be removed from the animal immediately, Thrift says. "Broken needles migrate in tissue, like a mini-knife. It is impossible to know where it could end up."
When deciding the length of the needle, it is important to consider the size of the animal you are vaccinating. "For intramuscular injections, I use 1-1/2 inch needle for fat cows or bulls, but a 1 inch needle is good for the majority of cows and calves. A longer needle could go all the way through the neck of a light weight calf."

For subcutaneous (just under the skin) injections, Thrift's needle of choice is a 5/8 inch B-bevel needle. "A B-bevel is designed for subcutaneous administration because it has a shorter edge, making it easier to get the injection under the skin. The bevel is less likely to pick up the top layer of muscle tissue." However, even with the use of a B-bevel needle, Thrift recommends tenting the skin (or pulling the skin away from the muscle to form a “tent”) to ensure a good subcutaneous injection.

Using a dull needle can also result in tissue damage and vaccine leakage, so it is important to change needles every 10 to 12 head.

So before you spend money on the vaccine, remember that the needle used to inject that vaccine is very important. Even if you own just a few head, you play a part in the safety of America’s food supply.
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