6 BULLETIN 1470, U. S. DEPARTMENT OF AGRICULTURE 
LAMB 
Lamb is a general term which refers to the flesh of young animals 
of the ovine species of both sexes. The age at which the change 
from lamb to yearling sheep takes place in the live animals is ap- 
proximately 12 to 14 months. 
Lamb carcasses as a group are distinguished from mutton car- 
casses by their smaller and softer bones, lighter-colored flesh, softer 
and whiter external and internal fats, smaller size of carcasses and 
cuts, and by the break joint of the forelegs. Of these the latter is 
most prominent. Lamb foreleg joints break in four well-defined 
ridges, resembling somewhat the teeth of a saw. These ridges are 
smooth, moist, and red with blood. The bones of the hind legs at 
this period also are streaked with blood. As lambs approach the 
yearling sheep stage the bones become harder and whiter and the 
break joints, although retaining some of the saw tooth effect, are 
relatively harder and more porous, and there is only a slight indica- 
tion of blood at the joint. Bones in lamb carcasses are easily cut 
or sawed. In the better grades the flesh is fine-grained, smooth 
and velvety, and light pink in color. 
The outer covering of fat is smooth, relatively thin and evenly 
distributed, and has a creamy or slightly pinkish color. Interior fats 
are of like quality and vary in quantity and evenness of distribution 
according to the grade. All fats lack brittleness and possess in a 
greater or less degree the softness and sheen characteristic of milk fat. 
This feature, produced by a milk diet, is especially pronounced in 
carcasses of hothouse lambs and to a lesser extent in spring lambs, 
most of which are marketed at or before weaning time and usually 
have not had access to feeds other than milk. 
Most lamb carcasses, except spring lamb which is marketed as 
such principally during April, May, and June, and hothouse lamb 
which is marketed during late winter and early spring, weigh 
between 35 and 45 pounds with the maximum range from 28 to 55 
pounds. 
SPRING LAMB 
The term " spring lamb " refers to meat from young lambs of 
weaning age or younger and which are usually sold for slaughter 
at ages ranging from 3 to 5 months. The flesh is uniformly tender 
and a shade lighter than that of more mature lambs. On account 
of the character of the feed, which is almost exclusively milk, such 
carcasses are referred to in some sections as " milk lambs." The 
bulk of spring-lamb carcasses weigh between 30 and 35 pounds 
with a limited number of carcasses weighing down to 20 pounds or 
below, and some up to 40 pounds. 
HOTHOUSE LAMB 
The term " hothouse lamb " refers to carcasses from animals which 
are produced generally under artificial rather than natural climatic 
conditions. The flesh of such carcasses is considered a delicacy and 
they are marketed during the late winter and early spring months, 
principally from January to March. They are produced under the 
most favorable conditions and represent unusual effort, care, and at- 
