Agriculture Reference
In-Depth Information
Vertebrae
Lumbar
Cervical
Thoracic
Sacral
Coccygeal
1
2
21
3
5
20
4
6
7
12
13
8
15
16
14
9
17
18
10
11
19
Figure 2.1
Skeleton of ox. 1, atlas; 2, 7th cervical vertebra; 3, scapula; 4, ribs; 5, pelvic girdle; 6, femur; 7, patella; 8, tibia; 9, tarsus; 10,
metatarsus; 11, phalanges; 12, humerus; 13, ulna; 14, radius; 15, sternum; 16, xiphiod process; 17, carpus; 18, metacarpus; 19, phalanges;
20, mandible; 21, cranium (by courtesy of Sisson and Grossman, 1975).
respectively. In meat animals, it consists of the number
of individual vertebrae shown in Table 2.1.
The
sacrum
is in the shape of a pyramid and formed of
three to five fused sacral vertebrae, except in the fowl in
which 14 fused lumbar and sacral vertebrae form the
synsacrum. The
sternum
or breast bone in mammals is
composed of six to eight fused segments. In the fowl, the
sacrum is a very large bone covering almost all of the
ventral part of the body.
There are generally the same number of
ribs
as the
thoracic vertebrae; they are divided into sternal or aster-
nal ribs depending on whether or not they articulate
with the sternum.
Carcase bones are valuable means of
identification
of
the different species of food animals, for example, where
substitution is suspected. Where the teeth of a bovine
animal are unavailable for examination, the
age
can
be estimated with reasonable accuracy by examination of
the carcase bones. This estimation is based on the degree
of ossification of certain parts of the skeletal system, the
most valuable of which are the cartilaginous extensions
of the spines of the first five dorsal vertebrae. Ossification
in these spines develops as shown in Table 2.2.
In
cows
, these changes take place more rapidly and the
cartilage has ossified after 3 years.
A further useful guide as to the
age
can also be
obtained from the ischiopubic symphysis. In cattle up
to 3 years of age, this can be cut with a knife, but after
this age, a saw is necessary. Similarly, the red bone
marrow of the vertebrae is gradually replaced by yellow
bone marrow, and distinction can be drawn between
movement (Fig. 2.1). It also acts as a blood-forming
organ, producing red and white cells, haemoglobin and
platelets.
The long bones of the very young animal are very
long, slender and smooth, with their prominences less
pronounced. With age, ossification of cartilage takes
place and the bone becomes more rigid. In the very old
animal, there is a decrease in bone organic matter,
making the bone more brittle and liable to fracture.
The proportion of bone in the dressed carcase of beef,
that is, the two sides, varies between 12 and 28%, accord-
ing to breed and bodily condition, being about 15% in a
good beef carcase and increasing with the age and weight
of the animal. It is lowest in Aberdeen Angus cattle but
is as high as 28% in second-quality cows. The average
percentage of the bone in lamb is 17-35%, in bobby
calves 50%, in veal calves 25%, in pork 12-20% and in
poultry 8-17%.
The skeleton of the meat animals is divided into two
parts: the axial skeleton comprising the vertebral column
or the spine, ribs, sternum and skull and the appendicu-
lar skeleton representing the bones of the limbs. The
foreleg contains the scapula, humerus, radius and ulna,
carpus, metacarpus and digits which are composed of
phalanges. The
hindleg
is made up of the pelvic girdle
(ilium, pubis and ischium), femur, tibia and fibula, tar-
sus, metatarsus and digits.
The
vertebral column
or spine is divided into five
regions - cervical (C), thoracic (T), lumbar (L), sacral
(S) and coccygeal (Cy), representing the neck, chest or
thorax, loins, sacrum (fused sacral vertebrae) and tail,
