That is not my point. Any breed has to have standards, whether it is accepted by the APA or not.
Is the California Gray basically the same size as the Leghorn? I do not understand why it is called a dual-purpose breed when the Leghorn is not.
Let me try this again. Overall weight is only one factor in whether or not a bird is considered suitable as a meat bird. Breeds and individual birds vary greatly in the proportion of live weight that is edible. A Leghorn has a greater percentage of its weight in the refuse portion of the carcass than does a California Gray. The weight of bone, offal, and other items must be subtracted from the live weight in order to determine the usable meat on a carcass. California Grays are closer to Plymouth Rocks in usable carcass portion than they are to Leghorns. There is also the matter of the type of meat, and its qualities and textures and distribution. This goes back to the point I made about subtle differences in conformation. By the early 20th Century, researchers had confirmed that Leghorn cockerels should be dispatched as young broilers due to the diminishing returns as they aged; their distribution of meat an percentage of weight made fattening them as roasters undesirable.
For example, a table done by a university student studying for his graduate degree at Cornell in the early 20th C found that a Plymouth Rock carcass provided 74% edible meat, while a Leghorn provided only 66%.
A study involving Desi, RIR, and White Leghorn cockerels done in India and published in the early 1950s found that : (Desi are an Indian fowl.)
~Therefore, as table poultry, the White Leghorn cockerels are inferior to Rhode Island Red or desi cockerels and occasion considerable reductions in returns. The percentage of edible viscera (heart, liver and gizzard) decreased, in general, with increase of live weight in all the three breeds. The percentages of edible meat in drawn (eviscerated) cockerels were highest in desi and lowest in White Leghorn cockerels at every stage of growth. The amount of breast meat in desi cockerels was more than in Rhode Island Red or White Leghorn cockerels. The percentage of breast meat in Rhode Island Red and White Leghorn cockerels did not show any significant differences. The percentages of leg meat (thigh and drum stick) in both Rhode Island Red and desi cockerels were more than in White Leghorn cockerels. There were, however, no significant differences in the percentages of leg meat in the Rhode Island Red and desi birds. As the birds for table should have a high proprotion of meat to bone
The Indian study went on to conclude:
~The determination of the percentage of edible flesh in the Rhode Island Red, White Leghorn and desi (indigenous) cockerels at 8, 12, 16, 20 and 24 weeks of age respectively revealed that the percentage of total edible meat was highest in the desi and lowest in the White Leghorn cockerels at all the stages of growth. The percentage of breast meat also was higher in the desi than in the Rhode Island Red or White Leghorn cockerels. As regards efficiency, the three breeds ranged themselves in the following descending order : The desi, Rhode Island Red and White Leghorn. The conformation of the dressed desi, Rhode Island Red and White Leghorn cockerels were classed as fully fleshed, fairly well fleshed and poorly fleshed grades respectively. REFERENCE