Brooches modelled in the shape of animals have been vastly recovered across all the Roman Empire, including Roman Britain. The distribution of archaeological finds suggests that the major production centres for such ornamentation were Britain and Gaul. Horse brooches are amongst the more common of types found amongst the zoomorphic repertoire, although enamelled varieties seem more common. Their popularity could be the result of the horse being a status symbol amongst the Celtic population.
For more information on Roman animal symbolism, please see our blog post: Animal Symbolism in Roman Art