The selection and sale of Guernsey bull semen is an important part of the Guernsey Society’s business and since 2000 has been based on the use of a specific Guernsey Merit Index (GMI). The GMI was developed by geneticist Dr John Woolliams in conjunction with a committee of Guernsey breeders who agreed on the priorities for breed improvement and within the Index the balance between Production and Type was set at approx 60-40 and GMI was the first UK index to give emphasis to Type Improvement (Legs/Feet and Mammary).