How they rank…
SIRE reference scheme rams are ranked using a scheme index compiled by Signet. This is an overall assessment of the economic value of an animal, combining estimated breeding values for eight week weight, scan weight, muscle and fat depth.
The index can be compared with those of all other animals in the same sire reference scheme. This is possible because all co-operating flocks use a proportion of similar sires by AI.
Values over about 130, depending on the breed, indicate rams which are faster growing and leaner than average for the scheme, but Signets advice is buy the highest indexed ram you can afford.