Many producers use the tail fossa — the hollow area under the base of the tail — as a subcutaneous injection site.

This may not always be a good idea, warns Tom Shelton, veterinarian with Intervet. “When you’re behind the cow, it’s easy to lift the tail and inject subQ in the tail fossa,” he says. “The problem is that a lot of injections, including most BST injections, are given in this area.” Over time, this can cause the formation of fibrous tissue, which can lead to a slower and less adequate immune response.