Basic Concepts of Animal Structure
Thursday, September 7, 2023
12:33 PM
Levels of organization in the animal
• Chemical- atoms, covalent bonds, molecules, proteins, lipids, carbs
• Cellular- nucleus, cytoplasm, membrane
• Tissue
○ Epithelial- cover body surfaces, form glands for secretion and excretion
○ Muscle- skeletal, cardiac, and smooth
○ Nervous- transmits information and controls body functions
○ Connective- support; adipose tissue and fat, cartilage and bone, blood
• Organ- groups of tissues with common function
• Organ systems- group of organs involved in common activity
Planes of reference
• Sagittal- runs length of body and divides it into left and right parts
• Median- type of sagittal plane that runs down centre of the body and divides it into equal halves
• Transverse- across body, divides it into cranial and caudal parts that are not necessarily equal
• Dorsal- at right angles to the sagittal and transverse planes, divides into dorsal and ventral parts
that are not necessarily equal
○ Called frontal plane in humans
Anterior (cranial)- towards head
• Superior for humans
Rostral- toward the nose
• Nasal in humans
Posterior (caudal)- towards tail
• Inferior for humans
Dorsal- towards upper part or back
• Posterior for humans
Ventral- towards lower part or belly
• Anterior for humans
Medial- midline
Lateral- away from midline
Proximal- towards the body
Distal- away from body
Deep (internal)- towards centre of body part
Superficial (external)- towards surface
Body cavities
• Dorsal body cavity- CNS
○ Cranial cavity in skull
○ Spinal cavity in spine
• Ventral body cavity- most soft organs (viscera)
○ Divided by diaphragm into thorax and abdomen
Male vs female for the breeding herd
male
sheep
pigs
poultry
cattle
ram
boar
cock (tom in turkeys)
bull
female
ewe
sow
hen
cow
Immature animals
• Heifer = immature female bovine
• Gilt = immature female pig
• Hogget = yearling sheep
Farrowing- birth in pigs
Neonates
chickens
turkeys
Chicks
males = cockerels
females = pullets
poults
ducks
geese
ducklings goslings
Castrates
• Steer = cattle
• Wether = sheep
• Barrow = pig
• Capon = poultry
Why do we have castrates?
• Beef
○ Steers finished in feedlots
○ From a growth performance basis (average daily gain, feed intake, feed to gain or
efficiency), bulls outperform steers
○ Bulls deposit less fat and more muscle
○ North American beef production is based on steers rather than bulls due to superior eating
quality (tenderness, juiciness, flavor)
• Pork
○ Barrows finished rather than boars
○ Pork production using boars is more advantageous from a growth performance basis and
carcass basis
○ Boar taint- problem with boar meat in which a fecal smell can sometimes be detected when
the product is cooked
• Lamb
○ Lamb quality not affected if rams or wethers fed
○ Often castrated to prevent breeding before being shipped for sale
Age and meat quality
• Cattle
○ 10-30 months- steers and heifers go to market
○ Bulls and cows can be held indefinitely in the breeding herd as long as they are productive
with no health, structural, or temperament issues
○ Beef from mature bulls and cows cannot qualify as high quality
○ As animals mature, deposition of connective tissue (including collagen) increases which
negatively affects beef tenderness
• Pigs
○ 6 months- barrows and gilts go to market
○ Sows remain in herd for 2.5 years
○ Boars can be retained indefinitely as long as they are productive with no health, structural,
or temperament issues
○ Chops and roasts in the fresh meat case are processed from youthful barrows and gilts while
the meat from boars and sows are used for processed meats such as sausages
• Birds
○ Broilers marketed at 4 to 8 weeks depending on target product desired
○ Pullets start laying eggs at 17-18 weeks
○ Meat from cage layers after a 12-month laying period is sometimes used for processed
poultry products
Pig body structures
• Snout- nose, mouth, jaw; movable tip of the muzzle
• Jowl- flabby, lateroventral part of the neck; used to make bacon
• Shank- fore- and hindlimbs
○ Metacarpals in forelimbs
○ Metatarsals in hindlimbs
• Flank- part of the under belly where the outer abdominal muscles are located; used to make
bacon
• Hock- bone in the hindlimb that is similar to the human ankle
• Shoulder- locomotion
• Loin- pork chops and pea meal bacon
• Rump- site of muscles associated with the hip
Cattle body structures
• Muzzle
• Dewlap- large median ski fold at the caudal end of the neck; helps get rid of body heat
• Brisket- lower part of chest cranial to forelimb
• Dewclaw- non-weight bearing digit on posterior of the forelimb
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No knee in farm animals (the knee in the diagram is actually the carpus)
Paunch- rumen
Cod- fat depot in males where the udder is in females
Poll- top of the head where horns emerge
Crest- muscling in the neck
Rib (forerib) and loin- middle meats, highest cost beef cuts
Hook and pins- 2 of the 3 bones of the pelvis
○ Hook is on the ilium and is prominent in lactating cows
○ Pins are the ischiatic tuberosity of the ischium
Pelvis
• Ilium (6)
○ Largest + most dorsal of the pelvis bones
○ Forms lateral walls of pelvis
○ Tuber coxae: point of hip or hook bones
• Iscium (8)
○ Projects ventrally and caudally
○ Caudal prominence: pin bone
• Pubis (7)
○ Smallest of the 3 bones
○ Forms cranial part of floor of pelvis
Lamb body structures
• Breast- analogous to brisket in cattle
• Dock- site of tail
Why is it important to identify structures?
• Assess breeding stock
• Assess health status
• Assess if individual animals need to feed differently to change body condition
• Assess pronounced masculinity
• Assess degree of finish
○ Body condition scoring (BCS)
 1 = not enough fat or muscle, place animal on a higher plane of nutrition to increase
muscle and fat deposition
 5 = too fat, can compromise reproductive performance, place animal on lower plane
of nutrition
Domestication- genetic change in plants/animals by humans through artificial selection
• Resulted in changes in:
○ Structure (more breast meat in chickens and turkeys)
○ Function (less ability to survive and reproduce in the wild)
○ Productivity (maximize performance and deal with harsh environments)
○ Carcass quality (larger, less fat, more muscle, more intramuscular fat)
○ Eating quality (improved tenderness, flavour)
Domestication of cattle
• Bos primigenius = predecessor of Bos taurus (common cattle), ancestor of Bos longiforns (first
domesticated cattle)
• Bos nomadicus is the predecessor of Bos indicus
• Bos indicus (Zebu cattle) found in tropical environments, better able to withstand heat and ticks
○ Differ from Bos taurus:
 Prominent shoulder hump of muscle supported by dorsal spines of the vertebrate
 Long face with drooping ears (floppy ears)
 Upright horns
 Small brow ridges
 Prominent dewlap
 Slender legs
 Uniform coloration (white, grey, or black)
 Heat and fly resistant
 Found in southern US crossed with Bos Taurus
Evidence for domestication
• Can look at bone structure from animal remains
• Examine gender of remains; more males killed with domestication
• Changes in structure and size
• Evidence of wear and tear in vertebrae
Introduction of cattle to North America
• Spanish brought Bos primigenius → Texas Longhorn cattle
• British and French brought Bos primigenius and longiforns to US and Canada
• Angus, Hereford, and Shorthorn breeds brought by British in 17-1800s
• Sebu (Brahman) cattle from India in 1905-1920 to southern US
• Continental European cattle brought in 1970s (Charolais, Simmental, and Limousin)
○ Heat tolerance and tick resistance
Breed differences in cattle
• 3 major classes in North America:
○ British breeds: Angus, Hereford, and Shorthorn; early maturing (deposit fat at young ages)
○ Continental breeds: Charolais, Simmental, and Limousin; late maturing and rapid early
growth with mature size
○ British-Continental crosses: often in feedlots
Importance of breed differences
• Performance in feedlot: average daily gain, feed intake, feed efficiency or conversion which
impacts time on feed, feed costs, cost of gain, and overall returns to the producer
• Cow-calf performance: maintenance costs to keep the cow and milk production to feed the calf
• Performance on the range: tolerance to the environment; being able to withstand harsh winters
and extreme heat
• Carcass traits: size of carcass, ability to fatten, muscling, marbling (intramuscular fat deposition),
size of cuts
• Eating quality: tenderness, juiciness, and flavor
Cattle alternatives
• Bison/buffalo: lower fat content
• Yak: from Mongolia, with better fatty acid profile
• Crosses with cattle: objective to bring desirable characteristics from other animals
Domestication of swine
• North American pigs descended from 2 species: Sus scrofa and Sus vittatus
• 3 types of pigs found in remains of prehistoric people:
○ Bones of wild pigs obtained from hunting
○ Bones from large pigs that were placed out to forage
○ Bones of small pigs that were kept in confinement
• Remains of domesticated pigs not found before Neolithic times
• European pigs had long snouts and legs
• 1880: Chinese pigs brought to Europe, bred with Sus scrofa
• 18-1900s: high energy content of pork important to meet energy demands of people
○ White-line breeds and crosses: maternal breeds
○ Dark-colored breeds: meat breeds
• Today: selecting pigs for leanness and against fatness
○ Breeds can be any colour
• Consequences of breeding for leanness:
○ Superior growth performance (gains, feed intake, feed conversion)
○ Desirable carcass characteristics with increased size and muscling and less fat
○ Problems with meat quality (tenderness and juiciness) due to temperament problems which
have affected pork quality
Domestication of sheep
• Goats and sheep were food production species to be domesticated
• 5 main groups of sheep:
○ Moufllon: Mediterranean
○ Urial: southern Russia
○ Argali: Himalayas
○ Bighorn sheep: Canada and eastern Russia
○ Domestic sheep (Ovis aries)
Domestication of fowl
• Chickens descended from red jungle fowl (gallus gallus)
○ Selection influenced by meat/egg production, feathering, hardiness, inability to fly, ability to
fight
• Ducks include Mallard and Muscovy
○ Palatability problems due to consumption of fish (fatty acids)
• Turkeys first domesticated by Incas in North America and brought to Europe in 1500s