KNOW BASICS Lecture 29: Introduction to Fat Deposition

Theres only1-2 questions on this lecture 😭😭

Adipose tissue

Simply, fat

Specialized type of connective tissue, composed of fat cells

Fat deposition

Fat stores present in animals that are essential for life

Internal fat depots protect vital organs

Fat cells can expand or shrink depending on amount of lipid stored in them

Fat gets deposited when energy inputs exceed energy requirements → Extra energy as fat

Body condition scores

3 is ideal

1-2 is too thin

4-5 is too much

Adipose tissue function

General classification → Connective tissue

Energy store

Thermal insulator

Mechanical shock absorber

Improves appearance of a finished carcass

Improves palatability or eating quality for meats

Role of adipose tissue

Carcass quality

Contains subcutaneous fat

Protect the carcass

Fat covering gives marbling for carcasses

More adipose tissue on beef and pork

Result in low returns for producer

Trim the extra fat = economic loss for producer

Carcass: Marbling

Intramuscular fat

Improves tenderness and juiciness

Better flavour

More marbling = better meat quality

Oxidation of this fat can cause off flavours/odors

Origin of adipose tissue → Mesenchyme

Originates from mesoderm in fetal development

One of 3 germ lines that produce all tissue in body

Synthesis of blood, skeletal tissue, lymphatic cells, connective tissue

Adipose cells precursors are globules that accumulate small droplets of lipid

Role of adipose cell precursor

Preadipocytes or adipoblasts

Resemble fibroblasts

Adipoblasts

• Produce white adipocyte

Myogenic lineage

• Produce brown adipocyte

Production will be stimulated by hormones

• Insulin, thyroid hormone, IGF1

Adipocyte

Has small amount of cytoplasm

Organelles pushed to one size

Once mature enough, it’ll store TAGs

Making the cell no longer able to divide

Can’t undergo hyperplasia

Adipose tissue deposits

Adipocytes accumulate

• Intramuscularly

  • Between muscles

• Subcutaneous or visceral fat

  • Under skin

• Intramuscular fat

  • Important for marbling

  • Near blood vessels and capillaries

Why adipose tissue is supplied by blood capillaries

If fat breaks down, it’ll travel through capillaries

If lipid needs to break down or get stored

Adipose tissue structure

Continuously grow → Hypertrophy

Depends on energy intake

If more energy intake = high hypertrophy

More energy will get stored

Fat cells can be used by animal for

Balance

Deposition

Mobilization

Net fat acceleration depends on

Release energy to make sure there is enough body

Depends on colder and warmer temperatures

Fat deposition and mobilization depends on

Rich supply of blood vessels

Enzyme systems → GI

Internal, visceral fat → Omentum

Thin adipose sheet

Over stomach and intestine

Allows structural support to stomach and intestine by hugging them

Internal, visceral fat → Mesenteries

Thin connective tissue membrane

Support intestine

Also called lace fat

Phases of fat/ where fat will deposited first

Phase 1:

• Internal visceral fat

• Omentum (Caul) and mesenteries (Lace)

Phase 2:

• Subcutaneous

• Intermuscular

Phase 3:

• Intramuscular

Why is the phases in this order

Visceral fat is important for organ protection and energy production

Intramuscular is less essential (but we want it in meat production)

Intramuscular fat will only appear if high excess energy → Extra amount of feed, gain weight

Factors affecting fat deposition → Breed differences in fattening

Early maturing cattle will deposit fat much faster

• British breeds

Late maturing cattle wont deposit fat as fast

• Continental breeds

Breeds are different in heigh, body composition, puberty, sexx, stress

Juiciness

Important for palatability of meat

Intramuscular is lower = less juiciness

Melted lipids → Make up broth that are released upon chewing

Melted fat → reduces moisture loss, minimize drying during cooking

Meat flavor

Carbonyl compounds in adipose tissue

Presence of specific FA impact flavour

Types of adipose tissue

White

• Main fat

• Support energy storage, insulation, cushioning

Brown

• Heat production

• Important for new borns and hibernating animals

Beige

• Can sometimes function as brown fat

• Usually has same properties as white fat

White fat composition and function

Important for energy storage

One large lipid droplet

Few organelles

Most abundant fat type in body

Brown fat composition and basic function

Heat production

Many small lipid droplets

Many mitochondria to produce heat NOT energy

Vascular → Heat produced from lipid oxidation and electron transport rxns

In newborns, cold adapted animals and hibernating animals

• None in piglets or poultry

Brown fat function

Heat generated by no shivering thermogenesis

Exposed to cold → shivering will happen

If cold is chronic → heat produced with no shivering

• T4, catecholamines both help with BMR and metabolism of fat

Fat metabolism in brown fat

Oxidizes FA

Energy released as heat NOT ATP

Phosphorylation important to produce ATP for contraction and relaxation in muscles

White adipose tissue FA metabolism

Release FA

Allow ATP synthesis

Energy storage: Pregnancy → Lipogenesis

Fat synthesis

Important at end of gestation for energy for fetus

Important after parturition to make milk

Energy storage: Pregnancy → Lipolysis

Fat breakdown

Make energy if too low in glucose

Problems in dairy cows

Build up of ketone bodies causing ketosis

FA metabolism

3 FA bound to glycerol backbone

FA in animal fats vary in length

Unsaturated and saturated FAs

Unsaturated have lower melting point because of kinks in structure