Fat Deposition ANSC 2340

What is Fat?

• specialized type of connective tissue, composed of fat cells

Where is Fat Located?

• beneath the skin

• between the muscles

• behind the eyes

• surface of the heart

• around the kidneys

• surrounding joints

• in bone marrow

• in the omentum of the abdomen

• within the muscle

What is the function of fat?

• essential for life

• protects vital organs

• extra reserve of energy

• insulation

• mechanical shock absorption

• improved palatability

What level of fat constitutes high-quality beef?

• 2mm fat cover

• marbling

What does marbling effect?

• tenderness

• juiciness

• flavour

• odour (due to oxidation of fats)

Function of the Mesoderm?

• one of 3 primary germ lines that produce all the tissue in the body

• responsible for synthesizing connective tissues

• synthesis of blood, skeletal tissue, lymphatic cells, connective tissues

• forms the mesenchyme

What is the Mesenchyme?

• the meshwork of embryonic connective tissue from which all other connective tissues of the body are formed, including cartilage and ultimately bone

What the precursors to adipose cells?

• preadipocytes

• adipoblast

Where are Preadipocytes and Adipoblasts found?

• wherever fat is found

What causes Mesenchymal stem cells to turn to pre-adipose tissue cells?

• stimulated by various hormones

• insulin, thyroid hormones, IGF-1, etc

What differentiates an adipocyte cell?

• nucleus, mitochondria, organelles, cytoplasm are all pushed to one side of the cell

• small amounts of cytoplasm

• low water content

• mature cells are >95% lipid/triglyceride

• cannot divide once it stores lipids

What is the definition of the Adipose Tissue Depot?

• sites in the body where there is an accumulation of adipocytes

Where are small adipose tissue depots found?

• between muscle fasiculi (intermuscular/seam fat)

Where are large adipose tissue depots found?

• under the skin (subcutaneous)

Why are Adipose Tissue Depots well supplied by Blood Capillaries?

• Delivers nutrients and oxygen – Capillaries supply adipocytes with what they need to stay alive and function.

• Allows fat storage and release – Capillaries enable the uptake and release of fatty acids and glycerol.

• Supports hormone function – Blood flow helps adipose tissue send and receive hormones quickly.

• Helps regulate body temperature – Especially in brown fat, capillaries help spread heat throughout the body.

What are the Key Characteristics of Adipose Tissue Depots?

• continuously grows depending on the energy intake vs. requirements of the animal

• can be mobilized depending on nutritional state of animal

• deposition and mobilization require supply of blood vessels and enzyme systems

When does Hypertrophy of the Adipose Tissue occur?

• periods of energy surplus

• when the cells have no more storage space, so new adipose cells must be made (hyperplasia)

• hypertrophy = cell growing in size → hyperplasia (new cells made)

How is fat mobilized in the body?

• mobilization = fat cells let go of fat for energy use

  1. Hormones like adrenaline or glucagon signal the fat cells.

  2. Stored triglycerides are broken down into free fatty acids + glycerol.

  3. These are released into the bloodstream to be used as fuel by muscles and organs.

What is Net Fat Accretion?

• the amount of fat your body stores over time

• the process of growth or enlargement by a gradual buildup

What does Net Fat Accretion depend on?

• energy balance

• lipid uptake vs. lipid mobilization

• hormonal regulation

• adipocyte capacity (how much space fat cells have)

What is the Omentum?

• thin sheet of adipose tissue located in a large fold of connective tissue

• located over the stomach and intestines

• aka Caul fat

What are the Mesenteries?

• thin connective tissue (CT) membranes that support the intestines

• aka Lace fat

What is Stage 1 of Fat Deposition?

• internal fat deposited

• visceral and kidney fat

• omentum and mesenteries

What is Stage 2 of Fat Deposition?

• subcutaneous

• intermuscular

What is Stage 3 of Fat Deposition?

• intramuscular

Why does fat deposition happen in these 3 steps?

• starts from the inside and goes outward

• inside: quicker storage, easier to use for energy, more blood flow

What types of Breeds are Early Maturing?

• British breeds

What types of Breeds are Late Maturing?

• continental breeds

What factors effect Intramuscular Fat Deposition?

• sex

• genetics

• slaughter age and weight

• hormones

• epigenetic modifications

• stress

• nutrition

• weaning age

What does Maturation Age have to do with Fat Deposition?

• early maturing cattle deposit fat earlier than late maturing cattle

Why can’t adipose cell numbers be genetically regulated?

• adipose cells can be formed from precursors cells (mesenchyme cells) that are similar to fibroblasts - they can always be made so genetics can’t stop this

Why are Adipose Cell Numbers not Nutritionally Regulated?

• extra adipose cells can be recruited from mesenchymal stem cells (MSC) to enable compensatory growth

Why is meat Juiciness Important?

• improves overall palatability

• limited juiciness = more dry, tough, etc

Where does Juiciness come from?

• intramuscular fat

• water levels

What does meat flavour come from?

• carbonyl compounds in adipose tissues

• the presence of specific fatty acids impacts meat flavour

What are the 3 types of Adipose Tissue

• brown

• white

• beige

What is specific to White Fat?

• function: energy storage - extra calories stored as triglycerides

• 1 central lipid droplet (large)

• fewer organelles

• most abundant (predominant type of fat in the body)

What is specific to Brown Fat?

• function: thermogenesis (heat production w/o shivering)

• many lipid droplets

• MANY mitochondria

• vascular - to distribute heat from lipid oxidation and electron transport reactions

• common in newborns, cold adapted animals, and hibernating animals

• none in piglets or poultry

What is specific to Beige Fat?

• in between white and brown

• gets activated by cold, exercise, foods and hormones

What is Thermogenesis?

• heat production without shivering

• thyroxine increases BMR

• catecholamine increase metabolism in all fats (specifically brown fat though)

What is Special about Fat Metabolism in Brown Fat?

• it oxidizes its own fatty acids

• oxidation is not coupled to phosphorylation

• produces heat, but not ATP

What is Special about Fat Metabolism in White Fat?

• releases fatty acids into the bloodstream

• used for ATP synthesis

Why is Phosphorylation important for Muscle Contraction?

• Phosphorylation activates proteins like myosin, allowing them to bind to actin and generate muscle contraction. This process is controlled by enzymes that add or remove phosphate groups.

What are the main roles for Adipose Tissue Depots?

• mechanical (shock absorption and protection)

• thermal insulation

• energy storage

When/Why does Feed Restriction occur in animal production?

When?

• During growth stages

• In breeding programs

• Before market

• During feed shortages

Why?

• Control growth rate

• Improve feed efficiency

• Support reproduction

• Improve product quality

When/Why does Feed Restriction/Starvation occur in nature?

When?

• During seasonal changes (e.g. winter, drought)

• When food is scarce or competition is high

• During migration or hibernation

Why?

• Natural food shortages

• Energy conservation (e.g. hibernation)

• Survival strategy during harsh conditions

What is Anabolism?

• building up

• synthesis

• ex. protein synthesis from amino acids

What is Catabolism?

• breaking down process

• ex. break down fat to energy

What is Lipogenesis?

• fat synthesis from excess carbs

How is Lipogenesis important for Pregnancy?

• at the end of gestation:

  • Stores extra energy as fat to support upcoming lactation.

  • Prepares body for high energy demand after birth.

• after parturition:

  • Supports milk fat synthesis for lactation.

  • Helps maintain energy balance when feed intake is low.

What is Lipolysis?

• fat breakdown into fatty acids and glycerol

What issues come from Lipolysis in Dairy Cattle?

• Early lactation (energy demand > intake)

Issues:

• Excess fat breakdown → high blood NEFA (non-esterified fatty acids)

• Fatty liver → liver can't process all NEFA

• Ketosis → buildup of ketone bodies = reduced appetite, milk drop

• Metabolic stress → weak immune function, poor fertility

What is the melting point of Unsaturated Fatty Acids?

• Monounsaturated: 10°C to 50°C

• Polyunsaturated: Below 0°C