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Animal Nutrition- 2


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Summary of Nutrient Absorption
1. Involves movement of end products of digestion from GIT to blood, lymph, or both

2. Occures by diffusion (higher conc.-->lower conc.) or active transport (movement of molecules that requires energy)

3. Most nutrient absorption takes place in the small and large intestines (villi aid in absorption)
adapted to a meat based diet and require a high quality, highly digestible source of nutrients.

Simple digestive tracts with little microbial activity. Require certain nutreints, such as pre-formed vitamin A and taurine (from consumed meat)
Animals that normally consume only plant material.

More complex digestive tract with symbiotic microbial activity that permits digestion of plant fiber
Animals that are not fastidious in their feeding behavior and consume a wide variety of animal and plant foods
Free choice water
maximum dry matter intake can be achieved only with free choice water available.

Inadequate water supply- when water is restricted, feed intake is reduced

Contaminated water- fould tasting water/water containing high level of total dissolved solids will result in reduced consumption of water and feed
acceptability of a feedstuff by an animal. Summation of taste, odor, appearance, texture and temperature of a feedstuff determine its degree of acceptance. Palatability may be affected by the chemical or physical nature of the food or both.
Chemical factors affecting palatability
1.Taste- probably the major component of the palatability complex. The major taste responses are:
sweet- enhances palatability
salty- ehance palatability
bitter/acidic- decrease palatability

2. Odors- produced by volatile materials. May serve as an attractant, but may not greatly influence total consumption

3. Secondary compounds- not involved in the primary processes of cellular metabolism, but have a secondary role such as in chemical defense:
alkaloids- N containing compounds
cyanogenic compounds- contain cyanide)
tannins- bind w/protein to make unavailable for animals
toxic amino acids

*chemicals protect plants from predators (bacteria, viruses, insects, and mammalian herbavores)
Physical factors affecting palatability
1. Prickliness or coarseness of various forages- can reduce palatability

2. Silica deposited in cell walls of many plant species- contribute to physical roughness/harshness; decrease palatability

3. Particle size- increased consumption observed if feed is creaced/rolled grain compared with whole grain
Dietary energy level
1.If there is sufficient palatability of feed most animals consume that quanity of feed needed to satisfy energy requirement until digestive tract can no longer accomodate the bulk in the diet.

2. Expenditure of energy- large amounts of energy expenditure will generally result in increased feed consumption

3. Dietary energy concentration- if a diet fed to an animal contains:
LOW concentration of energy- feed intake is high
HIGH concentration of energy- feed intake is low
*in either case, caloric intake is the same
Function, age, size of animal
1. Young/lactating animals generally have greater energy requirements and consume larger quantaties of feed per unit of body size

2. Size of animal- the larger the animal, the less feed it consumes per unit of body weight. Energy requirements of adult animals generally related to body weight to the .75 power
Environment Temperature
1. Zone of thermoneutrality or comfort zone- the metabolic rate of an animal is at a minimum when environmental temperatures are in a range that there is no energy demand on body temp. regulating mechanisms

2. As temp. decreases below comfort zone increases in metabolic rate necessary to maintain body temp and feed intake increases

3. Hot temps. have an inhibitory effect on food consumption

4. Specific dynamic action (SDA)- refers to the extra heat produced by the animal as a result of feed ingestion and the metabolism of its nutrients. SDA is the highest for protein, lowest for fat. Under conditions of high temps. dietary protein may need to be reduced and may be desirable to increase dietary fat levels.

5. Heat increment (HI)- sum of SDA and heat of fermentation. HI useful at temps. below comfort zone, and detrimental at high environmental temps.
Health of the Animal
1. Diseases and parasites reduce feed consumption

2. Certain metabolic problems (ketosis, bloat, diarrhea) and stresses (crowding, handling, noise) cause reduced feed consumption

3. Deterioration and contamination of feed/water cause reduced feed consumption
most abundant (non-water) nutrient

have characteristic ratio of atoms with empirical formula CH2O
Simple sugars that have only one molecule of sugar. These are grouped by number of carbons.

Most common sugars found in nature are pentoses and hexoses
Xylose- component of the plolysaccharide HEMICELLULOSE (cell wall of plants). found in other polysaccharides found in corn cobs and wood.

Arabinose- component of the polysaccharide PECTIN

Ribose- found in riboflavin and nucleic acids (RNA and DNA). Not needed in diet b/c synthesized from glucose within animal body.
GLUCOSE- blood sugar, also called 'dextrose' found in sucrose, lactose, maltose, and starch

GALACTOSE- 'milk sugar', component of lactose

MANNOSE- found in plant polysaccharrides

FRUCTOSE- 'fruit sugar' found in sucrose, honey, and semen

*Reducing sugars
Two monosaccharides linked by an acetal bond, the type of bond that links simple sugars into more complex carbohydrates
'table sugar'

most common disaccharide- GLUCOSE + FRUCTOSE

hydrolyzed by SUCRASE
'milk sugar'

GLUCOSE + GALACTOSE- beta 1,4 linkage

hydrolized by LACTASE

found mainly in mammory gland, enhance Ca uptake
created mainly when starch is broken down by amylase

GLUCOSE + GLUCOSE- alpha 1,4 linkage
component of cellulose

GLUCOSE + GLUCOSE- beta 1,4 linkage

No enzymes break beta 1,4 linkages in mammals or birds. Microbes produce enzyme to break bonds.
3-10 sugar units

Trisaccharide- Raffinose- occurs in small amounts in sugar beets, soybean, and cottonseed meals

Tetrasaccharide- stachyose- found in soybeans
many sugar molecules (>10)
alpha linkage of glucose units

3 types:
1. Amylose- unbranched plant starch, broken by amylase

*amylase breaks amylose into maltose which is broken by maltase into glucose molecules

2. Amylopectin- branched chain plant starch.

3. Glycogen- branched chain animal starch. similar to amylopectin, but more highly branched. Used as energy storage. 1/3 glycogen found in liver, other 2/3 found in muscles
most abundant polysaccharide in nature, has beta 1,4 linkage between glucose units.

linkage only broken by cellulase produced by microbes

mammals can't produce cellulase
mix of hexoses and pentoses

more digestable than cellulose
hexoses and pentoses mixed with salts of complex acids

found in fruits (sugar beets/citrus pulps)
mix of hexoses and pentoses
found in cell wall of plants, not considered a true carbohydrate, as proportions of C, H, and O are different from other polysaccharides.

Indigestable by all animals

found most commonly in forages of poor quality

lignification increases with age of the plant
Functions of Carbohydrates
simple sugars- especially glucose and ribose, are involved in energy transformation and tissue synthesis
starch- energy reserves in roots, tubers, and seeds
cellulose, hemicellulose- most important in providing support in living plants

source of energy
source of heat
building blocks for other nutrients
stored in animal body by converting to fat

*because most energy stored in the animal body is in the form of fat, dietary carbohydrates are not broken down immediately for energy and are stored in the animal body as fat or glycogen
Digestion and Absorption of Carbohydrates
Carbs. must be broken down to monosaccharides for absorption from the digestive system.

carbs absorbed in duodenum, broken into monomers by enzymes secreted by saliva and the pancreas. Glucose, galactose, fructose actively absorbed from the small intestine

carbs digested inside bacteria in the rumen. Broken down to glucose, galactose, and fructose then converted to pyruvic acid. Pyruvic acid is converted to volitile fatty acids (acetate, propionate, butyrate) with a loss of carbon dioxide and methane.
Volatile fatty acid production in rumen
glucose converted in the rumen to pyruvic acid via glycolysis by rumen microbes.

2 molecules pyruvic acid, each containing 3Cs, are formed from one molecule of glucose.

Pyruvic acid acid can be metabolized into any of the VFAs, which are absorbed from the rumen passively and rapidly
Acetate and Butyrate
Lipogenic- used for lipid synthesis
glucogenic- glucose synthesis after propionate in liver

*how animals obtain glucose

Propionate production is the most efficient conversion of feed energy to energy used by the ruminant animal.

Production of acetate and butyrate is less efficient because of greater generation of carbon dioxide and methane ( lost during eructation)
Evaluation of Carbs in plant cell wall
feed sample boiled with neutral detergent (loss of neutral detergent solubles) and left with Neutral Detergent Fiber (NDF).

NDF boiled with acid detergent (loss of acid dtergent solubles) and left with acid detergent fiber (ADF)

*NDF mostly cellulose and hemicellulose

*ADF mostly cellulose and lignin
Glucose Metabolism
glucose converted to energy within animal cells by 'final oxidative processes'- glycolysis, kreb cycle

1. glucose converted to two 3-C units (pyruvate) via GLYCOLYSIS which yeilds 8 ATPs and 1 glucose

2. Pyruvate converted to acetyl CoA which yields 6 mol ATP

3. Acetly CoA enters TCA or KREB CYCLE which yeilds 24 mol ATP


End result of kreb cycle is the oxidation of C and H to for carbon dioxide, water, and energy as ATP and heat. Energy contained within the high energy phosphate bonds of ATP used to drive various physiological processes such as:
muscle contraction
protein synthesis

*CO2 eventually exhaled by lungs and animal dissapates heat resulting from oxidation
Volitile Fatty Acids (VFA) metabolism
1. Acetate: not significanntly metabolized by the rumen mucosa or the liver, but rather by tissues such as muscle and adipose tissue.
Lipogenic- eventually oxidized in Kreb cycle, entering as acetly CoA. Also used in long chain fatty acid synthesis

2. Propionate: nearly all is metabolized in the liver where it gives rise to glucose or is metabolized via the Krebs cycle. Used to synthesize long chain fatty acids. Therefore indirectly contributes to fat synthesis

3. Butyrate: rumen converts ~50% of absorbed butyrate to beta- hydroxybuterate, which is an intermedieate in fatty acid oxidation that is eventually used in the krebs cycle as acetly CoA and the remaining butyrate is utalized by the liver. Very little butyrate found in blood, so not big role in fat synthesis

*only VFAs conveted to new molecule in rumen wall
insufficient intake of high priducing animals may cause catabolism of body reserves. Under these conditions, the 2C atoms from fat metabolism accumulate and produce toxic blood levels of ketone bodies.

cattle- early lactation
sheep- late pregnency
Diabetes mellitus
disease is diagnosed partly on the basis of higher than nromal levels of blood glucose when animal ISN'T eating.

common in humans, less common in animals

insufficient insulin production by pancreas

genetic basis; may be induced by overfeeding/obesity

high blood glucose
excess urinary loss of glucose
elevated mobilization of adipose tissue lipids
increased production of ketones
Organic compounds that are INSOLUBLE in water and SOLUBLE in organic solvents (ether).

Fats produce ~2.25 times MORE ENERGY than carbohydrates

Fatty acids are the basic units of fats
Fatty Acids
Consist of carbon chains 2-24 (or more) carbons long with methyl group at one end and carboxcylic acid group at the other end of the chain.
*General structure is:

Acetic Acid: CH3COOH
Myristic Acid: CH3(CH2)12COOH

*most fatty acids commonly found in animal tissues are strieght chained and contain even number of carbons.

*in wall of the rumen: branched chains and odd numbers of carbons mainly found in microorganisms)

Typical Formula:
Saturated Fatty Acids
Ex: acetic and myristic acid.

Each carbon has two hydrogens- NO DOUBLE BONDS
Unsaturated fatty acids
Have double bonds in the carbon chains

the greater the number of double bonds, the lower the melting point
alcohol component of all triglycerides commonly found in animal and plant tissues

Possible to have mono-, di-, or triglycerides--> and ester linkage with 1, 2, or 3 of the hydroxyld groups from glycerol
Simple Lipids
esters of fatty acids with various alcohols.

1. True fat: esters of fatty acids with glycerol

2. Waxes: esters of fatty acids with alcohols other than glycerol
Compound Lipids
esters of fatty acids containing nonlipid substances such as phosphorous, carbohydrates, and protein (+fatty acids +alcohol)

1. Phospholipids: fats containing phosphoric acid and nitrogen.

2. Glycolipids: contain carbohydrates and nitrogen (NO phosphoric acid)

3. Lipoproteins: lipids bound to protein in blood and tother tissues
Derived lipids
substances derived from simple or compound lipids by hydrolysis

fatty acids
other alcohols (sterol)- larger alcohols
Butyric Acid
Myristic acid
Stearic Acid
Oleic Acid
C18H34O2 (C18:1)
Linoleic Acid
C18H32O2 (C18:2)
Arachidonic Acid
C20H32O2 (C20:4)
Iodine Number
denotes the degree of UNSATURATION of a fat or fatty acid.

an unsaturated fat unites readily with iodine; 2 iodine atoms being added for each double bond

iodine number is the amount of iodine (g) that can be taken up by 100g of fat
Saponification number
measure of average chain length of the 3 fatty acids in a fat

lard and other high molecular weight fats contain practically no VFAs (RM# ~0)

Butterfat contains higher portion of VFAs (RM# ~20-33)
Melting point of lipids
temperature at which fat changes from a solid to a liquid state

MP dependent upon chain length and degree of unsaturation of molecule

As chain length increases, MP increases

As number of double bonds increases, MP decreases

*fats solid at room temp. (highly saturated)
*oils liquid at room temp. (highly unsaturated)
Phospholipids Composition
if X is choline- lecithin which is found in soybeans

if X is ethanoliamine- cephalin which is found in central nervous system
found in plant leaves

ruminents consume more than nonrumenents

Galactose is connected to glycerol

R=PUFAC (polyunsaturated fatty acids)
17 Carbons

If R group is:
glycine- glycochalic acid
Taurine- taurocholic acid

Types of hormones
Steroid- estrogen, progesterone, testosterone

Protein- insulin, somatotropin, glucagon
steroid that recieves bad press, but is essential to life

improtant in cell membranes for proper central nervous system function

precurser of other steroids- sex hormones and vitamin D
compound found in animals; precurser of vitamin D3
precurser of vitamin D2
Bile Acids
aid in digestion of fat
Physiological functions of fats and oils in the diet
1. Dietary energy supply

2. source of essential fatty acids:
linoleic acid (C18:2) and linolenic acid (C18:3)- can't be synthesized by animal tissues, so must be supplied in diet.
Arachidonic Acid (C20:4)- can be synthesized from linoleic acid- required if linoleic acid is absent

serve as carrier for absorption of fat soluble vitamins: during digestion, these vitamins absorbed along with fat in the diet.

Decreased efficiency of vitamin absorption if decreased fat

Other functions:
reduce dustieness- absorbs fines
enhances palatability- acceptance/eagerness with which an animal consumes its feed

lubricates pellet mill- results in harder, more firm pellets
functions of body fat for the animal body
protection of internal organs



energy storage
Location of fat
Animal body:
surrounding internal organs
marbling and milk

seed germ/embryo
Nautral sources of fat
most feeds contain low levels of fat (<10%)- cereal grains, forages, animal products

unprocessed oil seeds may contain up to 20% fat- soybean, cotton seed, sunflower seed
Basal Metabolism
minimum requirement of metabolism- only maintanance level

no nonvital work
not growing
not developing a fetus
storing no fat
yielding no product

requires work of:
the heart
other vital functions

Must have sufficient minerals

water required for all bodily functions

require linoleic acid and linolenic acid
Protein for muscle and connective tissue



minerals (Ca and P)

vitamin D (bone formation)
abdominal, intermuscular, and subcutanious deposition- undesireable

Intramuscular deposition (marbling desirable- make meat tender and juicy)
Provide nutrients for developement of fetus

build up nutrient reserves of animal's body to meet reuirements for milk production following parturition
protien- prolonged shortange decreases milk production

energy- fat and milk sugar

Ca and P

Vitamins A and/or carotine (precurser of vitamin A) and vitamin D

Assimilation of Ca and P for milk production
involuntary- heart and other vital organs

voluntary- work for recreation/economic production
wool fiber: practically pure fiber, high in sulfur.

Yolk:greasy part of wool make up of suint (potassium) and lanolin (wool fat)
Omega-3 and Omega-6 Fatty Acids
adipose tissue of fat contain several long chain unsaturated fatty acids not present in significant amounts in other fats. Important evidence indicates protective effect of fish oils against otheroschelerosis in humans

Consist of:
eicosapentoenic acid (C20:5)
docosahezoenoic acid-OHA- (C22:6)
Conjugated linoleic acid (CLA)
seceral isomers of linoleic acid exist in animal fats

In CLA double bonds are conjugated or adjacent to each other and are cis/trans rather than cis/cis as in linoleic acid

CLA isomers have been reported to be protective against cancer, diabetes, atherogenesis, and obesity as well as modulate immune function and bone growth
Nonruminent digestion and absorption of lipids
1. lipids etering the duodunum enter as a course EMULSION (dispersion of droplets of one liquid in another) with 2 IMMISCIBLE (not soluble in each other).

2. Bile Salts emulsify fat to increase surface area and make more available to LIPASE ( digests fat- breakdown triglyceride to get 2 non esterified fatty acids (NEFA) + one monoglyceride)

Bile cotains:
bile acids

3. Micelle- an aggregate of molecules of lipids and ile acids formed in the lumen of the GIT during preperation of dietary lipids for absorption

*5 types of fat in intestinal lumen:
bile acids, phospholipids, cholesterol, NEFA, monoglyceride: together form mixed micelle because different kinds of fat.

*micelles go to brush border, rupture, and are then absorbed
Ruminant digestion and absorption of lipids
Rumen- microbes modify lipids; very little escape unscathed

Fatty Acids-->free fatty acids + glycerol or other compounds

Bihydrogenation by microbes in rumen; follows lypolysis in rumen; results in addition of H to fatty acids with double bonds. Allows microbes to dispose of H; if carried to completion, all double bonds converted to single bonds and FA becomes saturated.
*Protozoa have largest effect on biohydrogenation
Ruminant synthesis of lipids
rumen microbes sythesize a wide variety of odd- carbon chain and branched chain FA, many with TRANS configuration.

*most plant material cis
Ruminent intestine
most fats enter small itestine as NEFA (non estrerified fatty acids), highly saturated and bound by insoluble complex to particulate matter

digest unsaturated FA to lower degree than nonruminent

*Saturated FA digested more completely in ruminents than non ruminents

mixed micelles do not have nonoglycerides because they are stripped off in rumen

primary lipids entering ruminent intestinal cells are saturated NEFA and phospholipids; only on occasion of rumen escape do monoglycerieds appear

*primary lipids absorbed into lymph system, not blood
Skin lesions
hair loss, poor feathering in chicks, reduced growth/reproduction

deficiency of certain essential FAs in monogastric diets
Fatty Livers
common problem of abnormal iver function is accumulation of lipids in the liver. Normally fat consititutes about 5% of weight of the liver, but may be as high as 30% in pathological conditions.

May arise from:
high fat/high cholesterol diet
increased liver lipogenesis caused by excess carbs.
increased mobilization of lipids from adipose tissues caused by starvation or hypglycemia
cellular damage to liver caused by infections/liver poisons like chloroform

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