The system was simple and effective. The female lines in the Gloucestershire Old Spots breed are divided into four colour groups shown below. Female offspring of all GOS females are named according to the BPA bye-laws, i.e. the daughter of the female carries the same family name as her dam preceded by the herd name of the breeder. Individual pigs within the same family are distinguished by numerals after the name.
The cyclic breeding system dictates that the male offspring are named according to the colour group of the boar’s dam and that the name given relates to the colour group to which he is to be mated. Thus, the male offspring of a sow in the Red group is always named Sambo, the Green group, Gerald, the Blue group, Rufus and the Black group, Patrick. On occasions when it has not been possible to stick rigidly to the cyclic system, this rule still holds true. For instance, if a Sambo boar is mated to a sow in the Green group, the male offspring are still named Gerald and mated to sows in the Blue group.
Boars named under this system should then only be mated to females in the group nominated in the diagram above. Sambos are mated to females in the Black group; Gerald to females in the Blue group; Rufus to females in the Red group and Patrick to females in the Green group.
It can readily be appreciated that once operating, this system is simplicity itself. A breeder can specialise in female lines from one colour group and use just one boar or a group of smaller breeders can co-operate together in keeping just one colour group and sharing a single boar. By using this system without deviation, inbreeding through the male bloodlines is minimised.