Composition

Composition is the aggregate of ingredients, their arrangement, and the integrated interrelationships that form a unified, harmonious whole. Steel spikes and steel tacks contain 100% steel. Even though differing in shape, size, weight, depth, length, and width, all have identical compositions. Unlike steel nails, meat animals consist of many components, as shown in Fig. 1.[1] They contain muscles, tendons, ligaments, bones, fat, organs, skin, blood, ingesta, and excreta. Each of these is subdivided into more specific categories and is expressed as a proportion of the live animal or any of its parts. For instance, the largest muscle in most animals is the longissimus thoracis et lumborum (commonly referred to as the rib and loin muscle), which spans the length of the back. By weight it represents about 4% of the live animal, 7% of the carcass, 12% of the total musculature, and 51% of the back muscles. The greatest economic emphasis is placed on increasing the mass of muscles in the animal in relation to everything else. The proportion of an animal's compositional endpoints is related to several criteria, but the three most important are visceral proportions, fatness, and muscling as expressed by the muscle/bone ratio. Livestock possessing high proportions of viscera are undesirable, as these organs have little value. A high proportion of fat is undesirable, as it requires trimming from the musculature. A low muscle/bone ratio is undesirable because it indicates the animal contains proportionately more low-value bone than high-value muscle.

Livestock at various stages of prenatal and postnatal growth vary in composition. Therefore, when variations in composition are assessed accurately, there is need to identify quantifiable measurements and factors affecting them.[2] Such factors include stage of growth, physiological maturity, nutrition, and genetics. The proportion of muscle in livestock can vary from below 35% to over 50%. This variation is more complicated when average compositions of species are considered as depicted in Table 1. Species alone accounts for at least 15% of the variation in muscle mass, because species differences in dressing percentages and muscle/bone ratios may vary by 30% and 3.2 respectively. As illustrated in Fig. 2,[1] there are several factors influencing dressing percentage including contents of the alimentary canal, pregnancy, presence of abnormalities (trimmed bruises, broken bones, etc.), methods of slaughter, sex, stage of growth, muscling, and condition of the hide or fleece, fatness, species and condition of the hide or fleece.

Figure 3[1] shows the interrelationships of muscle, bone, fat, and noncarcass components as influenced by stage of growth, fatness, muscling, and fill. For instance, when the effects of growth, fatness, and fill are constant, heavier-muscled livestock have proportionately more muscle, less bone, less fat, and higher dressing percentages than angular-shaped ones. Livestock that have more fill have proportionately less muscle.

I LIVE AMIMAL COMPOS1TIOH |

NONCARCASS

^0

HAIR ÍW00L) 6 SKIN

7 18

INGESTA 6 EXCRETA

JLÜ____

BI.OOP

8 20

Plasma

T 10 51

Erythrocytes

IE! 12. EE___

ORGANS

if 10

Nervous System

TTT---

brain, spinal cord

Tongue

l 1 6

Lungs & Trachea

J.^11___

Heart

1 1 10

Liver & Gallbladder

1 3 27

Pancreas

77T---

Spleen

< < ~T

Urinary System

~TT---

kidney, bladder

Reproductive Tract

< < k

Endocrine Glands

< < 2

pituitary, thyroid,

parathyroids, adrenals

genital (testes,

ovaries), (thymus)

ALIMENTARY CANAL

5 13

Esophagus

7TT---

Stomach

3 7

abomasum (rumen,

reticulum, omasum)

Small Intestine

1 3 26

duodenum, jejunum,

i 1 eum

Large Intestine

1 2 16

cecum, colon,

rectum

MUSCLES

Neck brachiocephali cus rema inder Thorax d iaphragma pectoral is profundus pectoral is superf. serratus ventral is remainder Thoracic Limb triceps brachii supraspinatus infraspinatus subscapulari s remainder Back long i ss imus psoas major S minor latissimus dorsi sp inalis trapezi us rema i nder Abdomen rectus abdominis transversus abdominis obliquus ext. abdom. obliquus int. abdom. cutaneus trunci Pel vie -Limb semimembranosus biceps femoris quadriceps femoris semi tend inosus gluteal group gastrocnemi us remainder

36 60

~T _7 12 _1_L3 TT' J_ _2. 3 IE' _< < T 9 "

1 2 3 22 jEHEZ"

IE-I Ilii'

_L JL 3 25." Il Ii 3E _3 _5 9 IE" -3 - H IL "

TENDONS & LIGAMENTS

Ligamentum nuchae Tendo calcaneus

FAT

6 l<f

27

Mesentery

~T 10 72

19

Per i renal

~T T IT ~~

--IT

Intraskeletal

J. JLJEH

— JL

SKELETON

k 10

38

Skull 6 teeth

(horns)

""25"

Coccygeal Vertebrae

2

Metacarpals 6

Phalanges

I 2 IT

--

Metatarsals &

Phalanges

1 2 17

T

Area of a combination of-carcassS noncarcass

Subcutaneous Intermuscular Cavi ty

Intramuscular Intraskeletal

16 27

Area of a combination of-carcassS noncarcass

—% of Ii ve an imal j—% of carcass or noncarcass % of major subcomponent |—% of minor first subcomponent .-% of d subcomponent

F'% of a combination of carcass 6 noncarcass parts

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