Unit 2: Nutrients Questions

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Unit 2: Nutrients A review of concepts relating to nutrient absorption

1. Diffusion • Simple Diffusion - is the process by which the molecules of a solvent or solute will attempt to disperse in order to establish an equilibrium

• Ex - if two salt solutions of differing concentrations are separated by a permeable membrane, then the concentrations on either side of the membrane will eventually average out (i.e., reach equilibrium) as the solutions are allowed an opportunity to mix

Osmosis - is a form of diffusion whereby the water moves across a semi-permeable membrane in an attempt to equalize the concentrations on either side of the membrane

• Think of what would happen to a single blood cell put into a drop of water

• Neither simple diffusion nor osmosis requires energy (e)

• The processes of simple diffusion and osmosis both follow the concentration gradient with the solvent of interest going from a region of high concentration to a region of swer concentration

• As a result there is no energy expended in movement of the solvent or solute

2. Active transport

• In the case of many of the nutrients absorbed in the digestive tract, they must often be absorbed against a concentration gradient

• Consequently, energy is expended during the movement of the nutrient from one side of the membrane to the other

• Cellular energy is called ATP Cells can also use transport proteins to move molecules against their concentration gradient. This also requires ATP

• Alternatively, many nutrients may be co-transported with sodium into the cell

• In order to re-establish the membrane potential, Na is pumped back out of the cell thanks to the sodium/potassim pump which consumes energy in the process (Na/K)

3. Pinocytosis • Also known as cell drinking

• A small number of selected fats and proteins may be absorbed intact into a cell through the process of pinocytosis

• Essentially, the cell membrane "swallows" the material to be absorbed and once inside the cell the material is released

• Requires ATP Deficiencies and toxicities Nutritional disorders may occur due to a deficiency or toxicity in one or more nutrients due to:

1. A direct increase or decrease of a dietary nutrient

2. imbalances — in rations

3. Abnormal soil conditions, production processes

4. Toxic plants, chemicals or drugs

5. lisease processes

6. Presence of anti-nutritional factors in the feed

Ex: Avidin in egg white interferes with biotin availability (vitamin B7) It is often difficult to isolate the problem and determine if multiple nutrients are involved If the nutritional problem is low grade the clinical signs are often vague making the diagnosis difficult.

Water

• Often overlooked, water is the single most important nutrient. ÷ Only oxygen is more important to maintaining life. , water is the most crucial • In terms of survivability nutrient.

• An animal can live after losing almost all its body fat, more than 50% of its protein, but a loss of >10-12%. of its water will be deadly.

• As a result animals can live longer (weeks) without food than without water (days).

• Water makes up to 90% of the newborn body, and 50 to 66% of an adult body. (As it ages the body loses water)

• Plays a role in nearly every physiological function essential to life Functions of Water 3 4 Thermaregulation Production of digestive juices Transport medium for metabolism products and excretion of toxins Involved in many chemical reactions

Lubricant 6 Involved in regulation of oncotic pressure.

1. Thermoregulation

• Water picks up heat produced by metabolic reactions and transports it away from the production area, with minimal body temperature change.

• Evaporation is a very efficient way to lose heat. Panting / Sweating

• The body's ability to constrict blood flow away from skin and extremities during cold stress helps in the conservation of heat if needed in periods of cold stress.

2 Production of digestive juices.

• Great amounts produced daily

3 Transport medium and solvent for various solutes in the blood, tissue fluids, cells and secretions, and in secretions as urine and sweat

Ex: Na/k (electrolytes)

4 A major factor in a lot of chemical reactions taking place in the body. In hydrolysis, water is a substrate in the reaction. In oxidation water is part of the end product of the reaction.

Ex C606H12 + 60г → 6CO2 + 6H20

5 Water is used as a lubricant to help in transport of semi-solid digesta in the intestinal tract. It also helps in the lubrication of joints and eyes, and provide cushioning of the C.N.S. Found in all body fluids

6 Regulation of oncotic pressure. Water moves into and out of the blood vessels via osmosis. Body's way of maintaining blood volume. Ex - when an animal becomes dehydrated their blood volume decreases. To maintain the blood volume water moves from the tissues into the vessels. Losses of body water All animals experience daily water losses thru:

• urine

Feces

• Sweat (panting) • respiration, sneezing (bird/reptile)

• Milk, nasal secretions, laying eggs, semen production, vomit, crying

******* bile (high fat diet) birth blood loss Urine is the body's way of excreting wastes from the body. Some water can be reabsorbed from the urine and from the feces. When the animal is in a dehydrated state the body can absorb more water from the urine and feces. Water intake must equal water losses. In the case of increased water loss from the body, such as diarrhea, water intake must be increased or dehydration will occur. The daily water consumption has to compensate for these continual losses.

Sources of water:

1 Metabolic - 5-10% of daily intake. Produced by the oxidation of fats, carbs and proteins

2 Food - Dry food 7% water Canned food is 80% water.

3 Water intake (drinking) - affected by:

• Аgе

• Size

• Life stage

• Food intake

• Food type

• Exercise

• Species

• Temp

• Health Factors affecting water intake:

1. Age: Young animals are made of approximately 80% water, geriatric animals can be as low as 50%. The younger the animals the higher the relative need of the animal.

2. Body size: the smaller the animal, the bigger the relative need.

3. Life stage: milk and eggs, muscle, fat, maintenance, growth Ex. Lactating cow needs 4-5 liters (of water) per lifer of milk produced (aug. 29L of milk perday)

Dry matter intake: Studies have shown that fasting dogs drink only a quarter of the water that a dog eating will drink. Not only will increasing the amount of food a dog eats increase the dogs water intake, but limiting water leads to diminished food intake.

Feed type: feed that contains lots of water needs less additional water intake. Increased fiber leads to increased water intake Increased protein/ minerals increases urine production which requires a greater water intake. Amount of exercise / work - Panting/ evaporation

Animal species: - Birds < mammals. Birds dont urinate - Cow (feces 80% water) us Sheep (dry feces) Ambient temperature and humidity: increase from 15 to 20C increases water intake 15-20%, increase from 22 to 30C increases water intake 300% General health

• Sick animals tend to reduce water (and food) intake Fever|Stress increase water needs • Kidney failure

• Thyroid Difficult to know exact water needs individual animals. Hence always give free access to water, since there is no danger for intoxication if the animals have not been previously deprived of water. "Water toxicity" is possible if previous prolonged deprivation. Most animals with free access to good quality water and a proper amount of a balanced diet will be able to accurately regulate their water balance through voluntary intake. Mechanism of water absorption

• Major site of water absorption is the large intestine (cecum and the colon) although water can be absorbed all the way along the digestive tract

• Water is absorbed into the body through OSMOSiS

• Water travels from a region where it is in high concentration to a region where it is in low concentration • No energy is required directly for the absorption of water

• Cells in the digestive tract use osmosis to absorb water by altering the concentration of salt on either side of the intestinal wall

• The major principle governing water absorption in the digestive tract is that "Water fallaws salt Volume Under normal conditions, animals consume 2-5 liters of water for every kg of dry feed consumed. Species able to conserve water better require less than others. cattle 4-1, sheep 2.5-1 to 3-1 If only a limited amount is available, or it is of poor quality, it can lead to: • infectious disease • toxicities -crustalluria -poor growth

Carbohydrates (CHO'S) They are the main energy source of animals and the main energy containing component of plants. (pg. 71, 87-95 ch 3)

In case of starvation the draw for energy is 1. glucose 2. glycogen reserve 3. fats 4. proteins Chemically contain carbon (C) hydrogen (H) oxygen (O) - (CH2O)

They are the link that enables animals to use the suns energy. Ex: Starch and Cellulose Carbohydrates, mainly glucose and glycogen, make up less than 1% of body weight of animals.

Primary role of carbohydrates is to provide energy. They make up the Largest component in most animal diets. Glucose , a simple sugar (monosaccharide), is immediately available to use for energy.

Excess glucose is stored as glucogen in the liver and muscles. CHO's provide much of the energy required by the body.

Classification based on: - Number of C atoms in the sugar molecule - Number of sugar molecules in the compound. Classified as • Mono Saccharides • Disaccharides • Oligosaccharides • Polysaccharides They are commonly referred to as sugars, starches and dietary fiber.

Saccharide = Sugar

1. Monosaccharides: Simple sugars > consist of one molecule of sugar • contain 3-7 C's > Glucose is the most utilized monosaccharide by the body Chemical formula c6H12O6 > Stored as glycogen > Fructose - same chemical formula as glucose but differs structurally (6 carbons) > Galactose - 6 carbons structurally different smallest a easiest Fagesost absorb

2. Disaccharides: Simple (compound) sugars > two monosaccharides linked Lactose is glucose and galactose Lactose is only carbohydrate of animal origin Sucrose is glucose and fructose Maltose is two glucose molecules • Linked by glycosidic bonds

3. Oligosaccharides and Polysaccharides: Complex CHO's • made up of long chains of monosaccharides • 3-10 oligo, >10 - thousands poly • requires more digestion before being absorbed into the bloodstream • e.g. Starch, fiber, glycogen > used for structure (cell wall) and energy (glycogen and starch) • Starch - polysaccharide consisting of only glucose molecules thousands joined by oligosidic bonds Dietary fiber - polysaccharides of plant origin that are not starch.

Dietary fiber can either be: • Soluble fiber the gut. - partially digestible by bacteria and protozoa in - Cellulose-partially soluble Ex: Pectin • Insoluble fiber - not digestible and does not contain calories. This helps to decrease the energy density of a food. Ex: Lignin - structural component in grass/ wood

Cellulose Hemicelluloses - Partially insoluble

Fiber is required for proper function of the gastrointestinal tract (GIT) and normal bowel movements, although an excess can lead to an increase in bowel movements, flatulence or constipation. Both soluble and insoluble fiber in moderation aid in GIT motility and movement of ingested food and help to collect debris and cells sloughed from intestinal wall - healthy Gl tract.

Monosaccharides units are joined together into disaccharides and polysaccharides by glucosidic bonds The digestion process breaks down the glycosidic bonds to make monosaccharides. Most CHO's in the body are absorbed as glucose - Water is the byproduct of CHO metabolism. Monosaccharide + monosaccharide = disaccharide + H2O<→ metabolic water comes from this There are 2 types of glycosidic bonds • 2- bonds (alpha bonds) - easily to digest/breakdown in saliva (saltine cracker) • B-bonds (beta bonds) - need microbes to breakdawn, we cant do it ourselves Starch consists of monosaccharides joined by a-glycosidic bonds. a-glycosidic bonds are broken down by digestive enzymes. Cellulose and other fibers consist of monosaccharides joined by B-bonds. These long chain polysaccharides are called Non-Starch Polusaccharides (NSP) ß-bonds are not able to be broken down by digestive enzymes in the body. Normal flora in the GIT contains enzymes which are able to break down these bonds, thereby allowing the body to utilize fiber as an energy source. Examples of NSP are: Cellulose - a structural component in the cell wall of plants. Consists of glucose molecules (tens of thousands) linked by B-bonds. Humans cannot digest cellulose 4 get energy trom it • Hemicellulose: made up by pentoses and hexoses (like galactose) found in cell walls of cereal grains etc. Pectin's I: in fruit and roots and bulbs of plants. Used as a thickening agent in jams. • Lignin: not a CHO, but is an insoluble fiber source. Structural component of plant walls. Different chemical formula from CHO's, contains N and different ratio of CHO Volatile Fatty Acids The breakdown of soluble fiber in the rumen, cecum and large intestine produce VFA's. These provide energy to the cells of the large intestine and are important for maintaining colonic health.

Some of the VFA produced include • Acetate (2 carbons long) • Propionate (3 carbons long) • Butyrate (4 carbons long)

CHO's functions: monogastric

Provide energy: Glucose

Storage of energy : Glycogen Building blocks for AA - protein sparing nutrients Building blocks for DNA Provides bulk and texture to diet Regulates transit time of food through intestinal tract

Only a limited amount of excess CHO's can be stored in the body as glycogen. The remainder is stored as fat If adequate CHO are supplied in the diet, the body will use it as an energy source, and leave the protein be used for tissue repair and growth. Digestion and absorption of carbohydrates Stomach (first step- microbes do their thing) Ruminants: the soluble fiber in the ruminant's diet is broken down by microbes. releases e for microbes - In the process they produce energy for themselves, gases and volatile fatty acids.

The animal absorbs these VFA's in the bloodstream and uses them as an energy source. • Different CHO's produce different amounts of VFA's • Starch produces more propionate, cellulose more acetate • some CHO's make it to the abomasum, and then into the lower digestive tract (same in monogastric) Non ruminants: very little digestion takes place before small intestines

Small intestines:

Process here is the same for ruminants, cecants and monogastrics. • Animal produce a-amylase capable of breaking the a-bonds in starch. ° The action of a-amylase results in he productions monosac honde breaking a-bonds starch)

• Monosaccharides Glucose - gets absorbed by absorptive cells of intestine

• Absorption into cells lining the surface of the villi happens with the help of a specialized transport protein Monosacchandes travel to liver, where fructose and galactose are converted into glucose. This glucose then either gets stored as glycogen or sent to the tissues as an energy source.

• Glycogenesis - synthesis of glycogen from glucose Large intestine most species absorb carbohydrates here Ruminants and monogastrics have relatively little digestion of NSP's in the large intestine. The small numbers of microbes in the large intestine of ruminants and monogastrics are able to ferment some NSP's, producing small amounts of VFA's.

• Provide energy for cells of the colon. This aids in maintaining a healthier colon and is why soluble fiber is an important part in the diet. In cecants, microbial fermentation of soluble fiber in the hindgut allows the animal to live on a diet of high-fiber materials that monogastrics would not be able to process.

• Fermentation in the cecum produces VFA's which are used as an E source.

Deficiency and toxicity:

Since CHO's are the main source of energy in an animal's diet, a deficiency in CHO's will cause an E deficiency. Energy deficiency: Energy deficiency is the most common deficiency lin vet. med.) Often complicated by a shortage of other nutrients

Caused by: Inappropriate feed • Due to poor management, poor ration balancing • Due to poor weather conditions drought, flood, winter, etc.

• Animals with increased energy demands * Lactation, Heavy work, growth, pregnant When energy is limited the animal relies on energy reserves in the body. First they will breakdown: cats will use

• Fats → change to carbs to use as energy protein first • Proteins. before fats The breakdown of fats and proteins create nitrogen waste and ketones in the body. These by-products must be excreted and put extra work on the liver and kidneys.

Clinical Signs of Energy deficiency are: > Weight loss > Decreased growth > Decreased conception rates > Increased mortality Energy toxicity: Toxicity is usually due to overconsumption and leads to weight gain. This leads to hupertrophy of fat cells. Also, the increased weight is hard on bones and joints. Often energy toxicity also goes with an increase of other nutrients.

Lipids (chapter 4/8) • Fats are lipids that are solid at room temperature (20C). Oils are lipids that are liquid at room temperature. • Chemically composed of Carbon, Hydrogen and Oxygen • Predominantly used for the production of energy. Has ~2.5 x more energy than an equal amount of CHO or protein • Beside essentio fatty acids there is no specific requirement for actual fat in the diet

Lipid categories: 1. Simple lipids 2. Compound lipids 3. Derived lipids

1. Simple lipids

• Fats: • 1-3 fatty acids bound to a glycerol

• Hydrophobic tails e.g. Triglycerides - most common fat in food and in the body

• glycerol + 3 fatty acids Fatty Acids : - Chains of carbon atoms - Carboxyl group on one end

Types of Fatty Acids: Depends on the number of hydrogen atoms.

-3 tupes: Saturated, Mono unsatunated, Poly unsaturated a) Saturated - no double or triple bonds between the C atoms in the fatty acid chain. Saturated in hydrogen. (mostly animal fat) H H hudrogenated oil = safurated oil)

Unsaturated (one double bond)

monounsaturated - one unsaturated bond (non-hydrogenated = unsaturated)

Poly-unsaturated oils) has several Il or Ill bonds. (mostly vegetable)

The melting point of a particular fat depends on: > Length of the fatty acid chain. The shorter the chain the lower the melting point is. (higher molecular weight, higher MP) > The saturation of the fatty acid chains. The more double and triple bonds there are in the fatty acids the lower the melting point. A double bond "bends" a molecule, therefore not allowing them to stack as closely together. This reduces the MP of the fat. 2. Compound lipids: • Simple lipid linked to a non-lipid molecule • Phospholipids - make up cell membranes. Contain a phosphate group instead of a glycerol. Glycolipids - lipios w/ a CHO atfacted-used for enorsy Lipoproteins - lipids bound to prosen (transport fat in blood) 3. erived lipids: Complex lipid molecules that include sterols (e.g. testosterone, cholesterol etc.) • Fat soluble vitamins CH, CHa fig: Cholesterol Functions of lipids 1. Fats provide the most concentrated form of energy. Triglycerides are the most common form of stored energy,. • Subcutaneous, around vital organs, membranes around intestines 2. Insulator and protector. 3. Myelin production for nerve cells.

4. Serves as structural components for cell membranes

5. Sterols act as hormones. Ex. Corticosteroids

6. Component of bile (cholesterol breaks down into cholic acid (bile acids))

7. Increases the palatabilitu of food and acceptable texture in companion animal foods. (risk of obesity)

8. Aids in the absorption of lipids, including Vit. ADD Fat in diet of Cont get absorbed (fat soluble vitamins)

9. Provides essential fatty acids. Required for many body functions including keeping skin and coat healthy 'essential →> mens body cont make them, must get from diet Fatty acids that the body cannot produce must be provided in the diet.

These are called essential fatty acids. Lindeic Acid (only one for the dog) C18:2 Omega 6 → 1st double bond touches the 6th carbon Found in vegetable oils Chicken and pork fat Used to synthesize linolenic acid in dogs and cats and arachidonic acid in the dog Linolenic Acid C18:3 Omega 3 Synthesized by linoleic acid. Omega 3 Fish and flax oils Soy oils

• Arachidonic Acid (Omega 6 (only essential in cats) (cats need meat in diet)

Found in meats - carnivores Fish oils are high in arachidonic acid • Pork and chicken have lower levels Dogs con make it All other fatty acids are formed in the body mostly in liver, mammary gland, and adipose tissue.

Function of Essential Fatty Acids

1. Precursors for Prostaglandin : Part of reproduction and parturition Inflammatory response

2. Structural components of cell membranes 3. Aids in the proper structure and function of skin and hair follicles Inflammation and pruritus can be altered by the ratio of omega 6 to omega

3 F.A. In dogs and cats with allergic pruritus a ratio of 5-1 to 10-1 of the omega 6 /3 has shown to greatly reduce pruritus. Omega 6 fatty acids, if added when lacking

Enhances skin - decrease water loss

• Increases food efficiency Shinier, glossy coat with decreased skin flaking Omega 3 fatty acids

• Decreases inflammatory reaction produced. (reduces inflammation) Useful before/after surgery, burns, trauma etc.

Deficiency and toxicity

Deficiency (based on EFA) Skin problems - scaly skin, poor hair coat, wound healing problems Fertility problems like sterility (males) and miscarriage in females • Increased susceptibility to infections Behavioral disturbances, kidney degeneration, arthritis like conditions, weakness Fat soluble vitamins not absorbed properly

Toxicity:

• Too many lipids of one kind may interfere with absorption of other fats: fat soluble vitamins, creating a shortage • Due to increase in palatability and the high energy levels it leads to obesity Lipid digestion and absorption

1. Non ruminants • Fat digestion usually does not occur until the small intestine salivary lipase enzyme may be found in saliva of some young animals such as calves on milk diets

• Once lipids reach duodenum sensors in the intestinal wall release cholecystokinin (CCK) which results in the release of bile from the gall bladder or liver b. Stimulates the release of lipase and co-lipase from the pancreas

• Bile emulsifies the large glob of fat into much smaller globs called micelles

Bilayer sheet

- This gives a large increase in total surface area of the fat and increases solubility of the fat. Bile salts can do this because they have a fat-soluble and a water-soluble part to their molecule.

Fat-soluble components of the diet - fat-soluble vitamins (A, D, E & K) and cholesterol are also found inside these micelles Pancreas releases lipase (enzyme) and co-lipase (co-factor) in a 1 to 1 ratio

Co-lipase binds first to micelle, lipase then anchors to micelles by binding onto co-lipase Lipase then digest the fat inside the micelle

• Digestion results in: small molecules

• free fatty acids (various sizes)

• a monoglycerides (single fatty acid attached to glycerol) large molecules

• glycerol

• absorbed through villi

• Short chain fatty acids and glycerol can be directly absorbed by the intestinal villa into the bloodstream.

• Monoglycerides and long chain fatty acids are absorbed into cells of the villa. Inside these cells they are converted back to triglycerides and are packaged with:

• cholesterol, phospholipids, and a small amount of protein to form lipoprotein aggregates called chylomicrons Lipoproteins aid to transport fat in the blood.

Chylomicrons are molecules of triglycerides, cholesterol and protein surrounded by a phospholipid. Allows fat to become water soluble and travel through the bloodstream. From the intestinal cells chylomicrons travel via the lymphatic system to the blood.

• More than 99% of dietary fat is absorbed by the end of the small intestines, so there is little digestion or absorption in the large intestines

2. Ruminants

• Fats are first subjected to microbia activity in the rumen.

• Rumen microbes produce fat-digesting enzymes that break the triglycerides into free fatty acids and monoglycerides Produce VFA's as well Almost all unsaturated bonds in the fatty acids are saturated during the fermentation process

• As a result, virtually all fatty acids leave the rumen in a saturated form

• The products of microbial fat digestion, because of poor solubility, drift out of the rumen with the rest of the digesta into abomasum and on to small intestine.

• Pancreas lipase and co-lipase are not required

• Only bile is required to facilitate the process of diffusion. Micelles form allowing for the small fat molecules to be absorbed by the small intestine.

• Fats are reformed into triglycerides and packaged into chylomicrons to travel through the blood. Summary of fat digestion:

1. Fat digestion in the non-ruminant is initiated in the small intestine, whereas in the ruminant digestion is initiated by microbes in the rumen

2. Absorption in both cases occurs in the small intestine with the aid of bile, which serves to emulsify the fat

3. In the ruminant lipase and co-lipase are not required because the lipids that reach the small intestine are already in a form that can be absorbed.

4. Short chain fatty acids absorbed directly into blood by passive diffusion

5. Long chain fatty acids are too large - absorbed into fatty walls of intestinal villi, reassembled into triglycerides, coated with cholesterol, phospholipids and protein to form a chylomicron, absorbed into the lymphatic capillaries eventually to larger arteries into bloodstream, then transports triglycerides where needed

6. Virtually all fatty acids absorbed by the ruminant will be saturated, whereas the saturation of fatty acids absorbed in the non-ruminant will be similar to the saturation in the original feed

7. Fat soluble vitamins are stored in the liver

Additional notes: Fats in food sources are vulnerable to oxidation damage (rancidity) This can decrease palatability of food (rancid smell and flavor) Antioxidants included in the diet will prevent oxidation of fats: • Synthetic = Tocopherols (synthetic form of Vit. E) • Natural = Vitamin E, rosemary, ascorbic acid Very unstable and easily destroyed during processing, resulting in low effectiveness as an antioxidant. Vitamin E must be added at a very high concentration to compensate for loss during processing