Lecture 3- Macronutrients

What are the three macronutrients?

Protein, fat/lipids, and carbohydrates.

What distinguishes macronutrients from micronutrients?

Macronutrients are required in relatively large amounts (protein, fat, carbohydrate); micronutrients are required in small amounts (vitamins, minerals).

What does "complete & balanced" mean in nutrition?

All essential nutrients are present in required amounts and appropriate ratios (e.g., Ca:P).

What is a macronutrient profile?

The % of metabolizable energy (ME) derived from protein, fat, and carbohydrates in a diet.

What is the macronutrient profile of a typical canine kibble example?

~25% ME from protein, 29% ME from fat, 46% ME from carbohydrates.

What is the macronutrient profile of a typical canine canned food example?

~32% ME from protein, 40% ME from fat, 28% ME from carbohydrates.

What are the two major roles of macronutrients?

Provide essential nutrients (amino acids, fatty acids) and supply energy (ATP).

Which macronutrient supports anaerobic metabolism?

Carbohydrates (via glycolysis).

Which macronutrients support aerobic metabolism?

Protein, fat, and carbohydrates (via TCA cycle).

Which macronutrient is most energy dense?

Fat (8.5 kcal/g using modified Atwater factors).

What are the modified Atwater factors for pet food?

Fat: 8.5 kcal/g; Protein: 3.5 kcal/g; Carbohydrate: 3.5 kcal/g.

What is heat increment?

The heat produced during metabolism; highest for protein (~30% ME), moderate for carbohydrate (~15% ME), lowest for fat (~5% ME).

What is protein composed of?

Amino acids linked by peptide bonds; arranged in primary, secondary, tertiary, and quaternary structures.

List general functions of protein/amino acids.

Muscle, skin/coat, hormones, enzymes, plasma oncotic pressure, acid-base balance, euglycemia (cats), and energy (not ideal).

What are signs of protein deficiency?

Muscle loss, poor growth, weight loss, anemia, poor coat, decreased pigmentation, taurine deficiency signs (DCM, retinopathy).

What is crude protein?

Nitrogen% × 6.25; includes amino acid and non-amino acid nitrogen.

Why is crude protein not always reflective of amino acid quality?

It includes non-protein nitrogen (e.g., urea) and does not indicate essential amino acid content.

What characterizes a good-quality protein?

High essential amino acid content, high digestibility, high bioavailability, minimal fermentation in the large intestine.

List essential amino acids for dogs.

Phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, arginine, leucine, lysine.

List essential amino acids for cats.

All dog essentials + taurine.

Are animal byproducts a good protein source?

Yes; organ meats are nutrient-dense and rich in essential amino acids, vitamins, and minerals.

Can plants be good protein sources?

Yes for omnivores; more challenging for carnivores due to incomplete amino acid profiles.

How can you assess adequacy of protein intake?

Muscle condition score (MCS), serum albumin, and comparison of diet to requirements.

What are the three major types of lipids?

Triglycerides, phospholipids, and sterols (e.g., cholesterol).

List general functions of lipids.

Energy, energy density, essential fatty acids, cell membranes, neurologic/retinal development, fat-soluble vitamin absorption, palatability.

How are fatty acids classified?

By saturation (saturated vs. unsaturated), number/location of double bonds (omega-3 vs. omega-6), and chain length (short, medium, long).

What are saturated fatty acids?

Fatty acids with no double bonds.

What are monounsaturated fatty acids?

Fatty acids with one double bond.

What are polyunsaturated fatty acids (PUFAs)?

Fatty acids with two or more double bonds; all essential fatty acids are PUFAs.

What defines omega-6 fatty acids?

First double bond at the 6th carbon from the methyl (CH3) end.

What defines omega-3 fatty acids?

First double bond at the 3rd carbon from the methyl (CH3) end.

List key omega-6 fatty acids.

Linoleic acid (LA), arachidonic acid (AA).

List key omega-3 fatty acids.

Alpha-linolenic acid (ALA), EPA, DHA.

Which fatty acids are essential for dogs?

Linoleic acid (omega-6), alpha-linolenic acid (omega-3), EPA/DHA.

Which fatty acids are essential for cats?

Linoleic acid, arachidonic acid, EPA/DHA (cats cannot synthesize AA).

What are short-chain fatty acids (SCFAs)?

<6 carbons; produced by GI microbes; include acetate, propionate, butyrate.

What are medium-chain fatty acids?

6-12 carbons; found in coconut oil; not essential.

What are long-chain fatty acids?

13-21 carbons; include all essential fatty acids.

What are chylomicrons?

Lipoproteins that transport dietary long-chain fats via lymphatics; reduce hepatic fat load.

List plant sources of fatty acids.

Leaves (ALA), seeds/grains (LA, ALA).

List animal sources of fatty acids.

AA from animal tissue; EPA/DHA from marine sources.

How can you assess adequacy of essential fatty acid intake?

Skin/coat quality; deficiency signs include dermatitis, dull coat, impaired neural/retinal development, poor growth, weight loss, immunodeficiency.

How are carbohydrates classified?

By fiber vs. non-fiber, molecular structure (mono-, di-, oligo-, polysaccharides), solubility, fermentability, viscosity.

What are non-fiber carbohydrates?

Digestible carbohydrates such as sugars and starches.

What are fiber carbohydrates?

Indigestible carbohydrates such as cellulose, hemicellulose, pectins, gums.

List functions of non-fiber carbohydrates.

Energy (aerobic/anaerobic), euglycemia, brain/fetal energy, lactose, glycogen, glycoproteins.

List functions of fiber carbohydrates.

GI health, microbial energy, motility, stool quality, glucose regulation, satiety, reduced energy density, altered digestibility.

What are the systemic effects of dietary fiber?

Improved glycemic control, microbiome modulation, immune support (IgA), altered nutrient digestibility, cardiovascular and reproductive benefits.

What are common carbohydrate sources?

Grains, vegetables, fruits, purified carbohydrates, glycogen (animal).

What is crude fiber (CF)?

An older measure of insoluble fiber; underestimates total dietary fiber.

What is total dietary fiber (TDF)?

A more accurate measure of total fiber content (soluble + insoluble).

What is nitrogen-free extract (NFE)?

Calculated non-fiber carbohydrate: 100 - (moisture + CF + CP + EE + ash).

What are examples of highly fermentable fibers?

FOS, inulin, chicory root, pectins, gums.

What are examples of moderately fermentable fibers?

Beet pulp, flaxseed, tomato pomace, pea fiber.

What are examples of poorly fermentable fibers?

Cellulose, peanut hulls, sunflower hulls.

How do carbohydrates help balance macronutrients in diet formulation?

When protein or fat must be restricted (e.g., renal or GI disease), carbohydrates provide necessary calories.

How can you identify protein, fat, and carbohydrate sources in an ingredient list?

Protein: meats, meals, legumes; Fat: oils, animal fats; Carbohydrates: grains, starches, vegetables, fruits.

What macronutrients can pet owners monitor at home?

Protein (via MCS), fat (via BCS/coat), carbohydrates (via stool quality/energy levels).

How do you know if a pet is consuming enough macronutrients?

Monitor BCS, MCS, coat quality, stool quality, activity level, and absence of deficiency signs.