2 BULLETIN 1470, U. S. DEPARTMENT OF AGRICULTURE 
Specifications for livestock and meat grades must be based on 
fundamental factors inherent in the animal or carcass, which are 
not subject to change on account of trade preferences, seasonal con- 
ditions or any other unstable or fluctuating factor. The specifica- 
tions or grade descriptions for meats prepared in the Department of 
Agriculture and recommended to purchasing departments of Federal 
and State institutions and commercial interests have been in practical 
use for approximately 18 years. Previous to this, since 1917, the 
grades had been in constant use in the Department's market-report- 
ing work. During a period of 23 years, the grades have become 
generally known by all branches of the trade and have been put to 
every practical test in the large markets of the country. 
The descriptions of grades of lamb and mutton appearing in this 
bulletin are, therefore, not new to the meat industry. To a large 
extent they represent the centralization and unification of ideas and 
methods of a large majority of representative slaughterers and 
wholesale and retail meat dealers throughout the United States. 
The application of the grades to the needs of the industry was thus 
made comparatively easy and it is hoped that their general adoption 
by all branches of the trade will not be long delayed. Already 
buying and selling in distant markets have been simplified to a 
marked degree. 
DEFINITION OF LAMB AND MUTTON 
" When does a lamb become a yearling sheep ? When does a year- 
ling sheep become a mature sheep ? " are questions often asked by 
the layman. Generally there are features peculiar to each of these 
groups by which it is not difficult to determine to which a given car- 
cass belongs. These differences are the result of changes which 
occur at different stages of maturity in the live animal. Age pro- 
duces marked changes in the character, color, and consistency of the 
flesh and bones and to a lesser extent in the consistency and char- 
acter of the exterior and interior fats. 
But there are periods in live animals when lambs are approaching 
the yearling sheep stage and when yearling sheep are approaching 
the mature sheep stage, when the blending of the several features 
is so gradual that exact determination of the group to which their 
carcasses belong is exceedingly difficult. At this period, the foreleg 
joints of many carcasses do not show what is known as a lamb 
joint, neither do they show the usual yearling mutton joint. 
Hardness and color of the bones are good indications of the age 
in all cases. Hardness of bones in carcasses can best be determined 
by observing the color of the ribs in the chest cavity and the bones 
in the shanks and in the break joint. Redness in bones indicates 
youth and whiteness in bones indicates age, and, to some extent, ar 
undernourished condition. These things considered in connection 
with the conformation of the carcass and color and texture of the 
flesh in most cases indicate whether it is lamb, yearling mutton, or 
mature mutton. From the standpoint of total slaughter and con- 
sumption at present, lambs constitute numerically approximately 80 
per cent, yearling sheep 10 per cent, and mature sheep 10 per cent. 
