Needles

4.8.2 Needles Needles come in different lengths and bore sizes (i.e. diameters). On the base of the needle or needle package, the length is indicated in inches or centimeters, and the bore size is indicated as a "gauge." It is usually written like this:

"16G x 1" This means a 16 gauge needle that is one inch in length.

length=1 inch bore size = 16 gauge LENGTH Most medicines for livestock require a needle 1 to 1.5 inches in length. For subcutaneous injections, 1.0 inch needles are sufficient, although 1.5 inch needles can be used. For deep intramuscular injections, choose 1.5 inch needles if you have them, except in baby livestock where 1 inch needles are sufficient.

DIAMETER OR BORE SIZE

Most medicines for livestock require 16 to 22 gauge needles; the larger the gauge, the smaller the bore size. The choice of bore size depends on the animal species and size as well as the "viscosity” (thickness) of the medicine.

For baby livestock, 20 or 22 gauge needles are appropriate, unless the thickness of the medicine requires a larger bore. For example, most penicillin cannot be given through a needle smaller than 19 gauge. In adult livestock, 16 to 19 gauge needles are used depending on the thickness of their skin. Large bore (small gauge) needles make it easier to inject medications and don’t bend as easy as small bore needles. But more medicine can leak back from a large bore injection site and be wasted.