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Animal Nutrition Test 3
Terms in this set (142)
polyhydroxy(OH), aldehydes, and ketones (C=O): constitute about 2/3 of the diet
Nutrient Requirements for Carbs
NO requirements for CHO, Carbohydrates are not required, will list energy requirements, CHO are the major suppliers of energy in most diets
CHO are usually
the cheapest source of energy, abundant in plants, and represent 70% of diets
Pentoses and Hexoses
Not a major CHO in feeds and very few exist as a monomer. Xylose(pentose) is a component of hemicellulose
Include glucose, galactose, fructose, and mannose
Carbs have no requirements b/c
carbs aren't needed to build anything specific, proteins can be used to do the duty of Carbs
Fiber Carbohydrates are usually
harder to digest
Connected by glycosidic bond (Sucrose(fructose and glucose)Lactose(glucose and galactose), Maltose(glucose and glucose), and Cellobiose(glucose and glucose))
include compounds with α 1-4 or α 1-6 linkages.
Amylose: glucose polymer with α 1-4 linkages (straight chain)
glucose polymer with α 1-4 and α 1-6 linkages(Not straight chain, because α 1-6 linkages cause branching)
α 1-4 vs α 1-6
#= position on chair configuration
Animal version of amylopectin (branch chained glucose polymer) Can be stored as glycogen in liver, muscle, and blood. Branched, both α 1-4 and α 1-6
Straight chain glucose polymer, but unlike amylose, it contains β 1-4 linkages.
Animal enzymes can hydrolyze
α 1-4 linkages but NOT β 1-4 linkages.
digest fiber because they have enzymes that can break the β 1-4 linkages.
2 monosaccharides together
Cellulose is another compound with
β 1-4 linkages, but it is a glucose dimer, not a polysaccharide.
Liver has more
glycogen per mass than muscles
1/2 glucose of monogastrics
Only microbes break
β 1-4 bonds (ruminants and hind-gut fermentors)
Composed of 5 and 6 carbon sugars and uronic acid in a polymeric form. Heterogeneous (not all hemicellulose are the same and that the ratio of 5 and 6 carbon sugars and uronic acid may vary depending on the plant) Often associated with lignin
a polysaccharide rich in galactouronic acid, rich in α 1-4 linkages. Similar to hemicellulose however, it is less lignified and, therefore, more digestible. The α 1-4 linkages result in greater digestibility. Examples of pectin= apples, citrus, fruit, carrots, beans, soybean hulls
A polyphenolic compound. One of the major polyphenolics present in lignin is hydroxy, methoxy, phenylpropane. Cell wall component is often assumed to be a "fibrous" carbohydrate. Lignin is NOT a true carbohydrate. Heterogeneous. Lignin forms cross linkages with cellulose and hemicellulose and this association is what provides the structural rigidity to plants.
As lignin content of the plant increases
the digestibility of cellulose and hemicellulose decreases. As age of plant increases the lignin content increases
Most abundant starch
Most abundant starch carb. and major CHOs in forages
cellulose and hemicellulose
Starch (glucose polymer)
The major CHO in cereal grains
more lignin than grasses
Primary vs Secondary Cell Wall
The primary cell wall is very thin and contains mainly pectins and hemicellulose, it is lignified. The secondary cell wall is thicker and comprised mainly of cellulose.
center of cell that contains water soluble CHO such as starch and sugars
In between the cells. About 70% lignin. Provides the strength to the cellulosic plant skeleton. Middle Lamella (along with lignin) provide the strength to the cellulosic plant skeleton
Crude Fiber (CF)
Is the organic residue remaining after digesting with 0.255N H2SO4 and then 0.313N NaOH. The compounds removed are predominantly proteins, sugars, starches, lipids and portions of both the structural carbohydrates and lignin.
Limitations of Crude Fiber
1) It treats all fiber components (cellulose, hemicelluose, and lignin) as uniformly digestible. Ruminants (microbes) can, however, utilize some cellulose and hemicelluose though lignin is essentially indigestible
2)Not all of the lignin and hemicelluose is recovered by the crude-fiber method. As a result, a portion of these components is included in the nitrogen-free extract (sugars and starches).
How can we improve fiber/plant digestibility?
Less lignin, find way to make plants with less lignin(Alfafa), but less lignin= less growth/more pests
Van Soest method
separate feed dry matter into two fractions (one of uniform digestibility and one of non-uniform digestibility). Feed samples are boiled in NDS and components are separated
Neutral-Detergent Solubles (NDS)
consisting mainly of lipids, sugars, starches, pectins, proteins, and NPN with a digestibility of about 98%
Neutral-detergent Fiber (NDF)
consisting of plant cell wall components: cellulose, hemicellulose, lignin, as well as minerals. more closely corresponds to the true fiber fraction than crude-fiber analysis. NDF= 100%- NDS. NDF is not a uniform chemical entity, its overall nutritive value is considerably influenced by the amount of lignin present. (better way to measure fiber)
Acid-Detergent Fiber (ADS) Analysis
ADF residue contains: cellulose and lignin
NDF- ADF= hemicellulose
Three major parts of corn kernel
endosperm, germ, and pericarp
80-84% of the kernel. Contains about 85% starch, and about 12% protein.
10-14% of the kernel. 85% of the oil in corn is found in the germ. There is some CHO and protein in the germ as well
The outside of the kernel. Approximately 6% of the kernel. Mostly non-starch CHO and contains small amounts of protein and oil. Waxylike appearance and protective coat. Microbial and host enzymes have a difficult time penetrating the pericarp. That is why it is imperative to process corn to break the pericarp so that enzymes may have access to the starch.
People can be vegetarian b/c
vegetables can have other nutrients like protein that is digestible along with lipids and minerals, even though cellulose and hemicellulose can't be digested but helps move food along digestive tract, pure cellulose and hemicellulose is undigestible to monogastrics and you can't live off of it.
When lignin is associated with cellulose and hemicellulose
it makes these carbs less digestible for microbes
Crude Fiber removes lignin so
crude fiber underestimates amount of fiber
Hydrolytic digestion of CHO begins in the mouth for many animals. Saliva contains amylase which hydrolyzes α 1-4 linkages to form dextrins and maltose. Dextrins are short glucose polymers. Salivary amylase is NOT a major contributor to starch degradation!
End Product of Amylase
In contrast to what many seem to think, the end product of amylase digestion is not glucose. It yields maltose, which is NOT further acted upon by amylase. Ruminant saliva does not contain amylase.
The low pH of the stomach or abomasum does lead to the
breakdown of some CHO, e.g. fructosans, but once again, this is of minor importance in the grand scheme of CHO digestion!
1st step of NDF
NDS(using neutral detergen that solulizes(removes) NDF
NDF IS NOT
a uniform chemical entity, its overall nutritive value is considered influenced by the amount of lignin presnt
Why do we want NDF for ruminants and Hind-get fermentors instead of CF like monogastrics?
b/c ruminants and hind-gut fermentors consume more fiber than monogastrics, and b/c ruminants and hind-gut fermentors can digest fiber b/c of microbes so need proper quantification of amount of true fiber in diet
NDF is a
truer fiber fraction than crude-fiber analysis
Maltase, isomaltase, sucrase, and lactase associated with the brush border (microvilli) along with pancreatic amylase act to hydrolyze CHO. Maltase cleaves α 1-4 linkages and isomaltase cleaves α 1-6 linkages.
In addition to hydrolytic digestion by enzymes produced by the host animal
there may be digestion by microbial enzymes as part of their fermentation.
Most microbes are
anaerobic, that is they survive only in the absence of O2 . Some are facultative anaerobes (can tolerate some O2 )
Condition required for adequate fermentation
Temperature of 38-39*C, Constant food(nutrient) supply, constant removal of fermentation end products, pH (5.5-7), constant mixing, and constant osmotic pressure
Further digestion of fiber
can be bad because destroys needed fiber
CF __ fiber amount
Older plants have bigger
NDF tells us
amount of fiber but not how digestible it is b/c exact lignin content is unknown
NO analysis for
cellulose and lignin
Low pH of stomach or abomasum leads to
some breakdown of CHO but very little b/c main CHO digestion occurs in small intestine
1 glucose -glycolysis-> pyruvate -->
lactase(3C) or: based on bacteria diet feed= formate(4C), lacetate(2C), or propionate(3C)
Bacteria, protozoa, and fungi. Most= bacteria least= fungi
There are a lot more bacteria than protozoa in the rumen, but
because protozoa are much larger, there is approximately equal biomass contributed from each.
Animals are born WITHOUT
bacteria, protozoa, or fungi in the GI tract. Microbes are introduced to GI tract during birth (microbes in birth canal), via food and air, and grooming
mobile (flagella or cilia), search for food (bacteria) in rumen, protozoa can float and stay in rumen longer. Are important because they eat starch and drop pH
Amount of bacteria > protozoa in SI b/c
unlike protozoa they cannot determine their movements and are washed out of rumen and digested into bacterial protein in abomasum
Feeding oils (and fatty acids and less protein) to cows
suppresses protozoa, bacteria grow more and replace protein as nutrient source
Protozoa-free (defaunated) ruminants can be created by
immediately isolating the newborn or can be created by treatments (lipids or detergent). They will stay protozoa-free unless they are brought into contact with an animal that has protozoa in the GI tract.
Protozoa- free ruminants
do just fine, showing protozoa is not required for fermentation
NEEDED in rumen
Pyruvate can be converted to
lactate (another 3 carbon compound), but more often it is converted to formate (1 carbon), acetate, (2 carbons), or propionate (another 3 carbon compound).
Formate can be converted to
CO2 and H2 and in turn, CO2 and H2 can be used to form methane (CH4).
Two moles of acetate can be used
to form one mole of butyrate (a 4 carbon compound)
Acetate and propionate can form
valerate (5 C compound)
The amount and ratio of end products of glucose fermentation vary
depending on the conditions in the rumen
1 mole of glucose (6 C sugar) is degraded via glycolysis to
2 moles of pyruvate (3 C compound)
little glucose in rumen b/c
eaten by bacteria
propionate, acetate, and butyrate
A function of amount and type of diet
dictate bacteria diet
Fermentation Balances can be used
to describe the conversion of glucose to end products as well as the conversion of glucose to end products
Fate of glucose depends on
diet and types of microbes present
energy, if not stays in epithelium
The efficiency in which energy is retained when glucose is converted to the major VFA
It is most efficient if glucose is converted to
propionate and least efficient if it is converted to acetate or butyrate.
Conversion of acetate and butyrate results in the
"loss" of a carbon and the production of methane
Fermentation diet depends largely on
DMI and diet. This affects the turnover rate of rumen contents, pH, and the microbial populations in the rumen.
Results in an acetate type fermentation (fat increases)
Results in a much closer ratio of acetate to propionate (fat and glucose)
Diets that have finely ground forages
will also result in a more even ratio of acetate to propionate. Diets with finely ground forage act like high grain diets because the animal does not ruminate as much; therefore, the rumen pH is lower.
Diets that result in high propionate production
favor fattening and low milk fat test
Too much grain in diet
About 60 to 70% of the energy absorbed from the ruminant GI tract is in the form of
About 70% of gas produced is -- and 30% --
There is lower energy loss as CH4 as
Ways to minimize energy loss as CH4
1) Feeding diets that favor propionate (glucose)
2) Stimulate butyrate formation from acetate b/c H2 consumed (2 acetate + 2H2 is converted into 1 butyrate and 2 H20). However is difficult to stimulate butyrate production when feeding practical diets
3) Feeding ionophores such as monensin and lasalocid which reduce CH4 production
4) Feeding PUFA may reduce CH4 production. PUFA are to a great extent saturated in the rumen. This event consumes H2 . However, due to the limited amount of fat that can be added to ruminant diets, this is not going to result in a significant reduction in CH4 production.
are antibiotics, which tend to eliminate hydrogen producing bacteria and shifts microbial populations such that propionate formation is favored.
In production agriculture, it is desirable to
maximize fiber digestion in the rumen
Why maximize fiber digestion?
.More fiber digested; more energy extracted from fiber
.More fiber digested; more energy extracted from fiber
.More fiber digested, higher production levels
•More fiber digested, more microbial growth
•More fiber digested, better rumen environment, which means healthy bugs and healthy animals
Factors affecting fiber digestion
. Degree of lignification (as lignification increases, fiber digestibility decreases)
. When the amount of grain in the diet increases, rumen pH decreases, and this discriminates against fiber digesting microorganism, which prefer higher pH
. Grinding or pelleting forages usually decreases fiber digestion due to the increase in rate of passage and reduction of retention time in the rumen
.Addition of fat, particularly those that are rich in PUFA may cause a decrease in fiber digestion. The exact reason for this is not known. It may be toxic to fiber fermenting bacteria. Fiber digestion is less affected by saturated fats. "Inert fats"
. physical effect (fullness)
Starch digestion is __ than fiber digestion and __ than that for simple sugars
In production agriculture it is desirable to
maximize fiber digestion as it increases production levels, microbial growth, and leads to a better rumen environment
High energy diet
less filling, but what is consumed is more satisfying
Neither silage or hay will be as nutritious as
The rate of starch digestion can vary considerably depending on the
nature of the starch
Starch can be present in a __ or __ form
crystalline, gelatinized. Gelatinized= more rapidly digested
Why are cereal grains processed?
to convert crystalline starch to gelatinized starch in order to increase the rate of digestion/fermentation. Heat and moisture are the most effective treatments (Steam-flaked)
Prior to domestication, ruminants evolved consuming
high forage diets. Therefore, it is not surprising that overconsumption of grains can lead to metabolic complications S
How come grinding corn is more/less digestible than grinded forage?
Starch digestion rate isn't as affected than fiber, breaking pericarp will take time
Acidosis can result when
excessive consumption of grain( too much fiber) results in a drop in rumen pH. As pH drops, lactic acid producing bacteria begin to predominate. Lactate production increases in the rumen and upon absorption from the rumen, it is slowly utilized by tissues. Consequently, the concentration of lactate increases in blood and blood pH drops. Hemoconcentration of blood occurs, blood pressure drops, and heart rate increases. If these reactions are severe, the animal may die.
Acidosis subclinical vs clinical cases
Subclinical=may cause daily fluctuations in intake that are undetected, yet detrimental to rates of production
Clinical= visible symptoms
Symptoms of Sub-acute ruminal acidosis (SARA)
Reduced rumination • Reduced DMI • Mild diarrhea • Foamy feces (gas bubbles) • Undigested grains (in large amounts)
Ionophores may be effective in controlling
subclinical acidosis. They can cause a reduction in the numbers of Streptococcus bovis, which is a major lactate producing bacteria in the rumen.
associated with over consumption of high grain diets (too much fiber). Chronic low pH in the rumen causes lesions or ulcerations of the rumen epithelium.
Over consumption of grain may cause
displaced abomasum (DA) in ruminants. The exact cause of DA is not known, but it may depend on a flaccid rumen due to the lack of high fiber feed (like a basketball without air) allowing the abomasum to shift position. It also may be related to increased gas production in the abomasum. The disorder is also called twisted stomach, because the movement of the abomasum from it normal position causes a twisting of the GI tract such that digest no longer flows through the animal. Death (via lack of feed intake) results unless the abomasum can be manipulated back to its normal position or surgery is done to correct it
Glucose is the primary
CHO monomer absorbed by the non-ruminant GI tract.
In the ruminant, very little glucose is absorbed
due to rumen fermentation
In ruminants, glucose is derived primarily from
propionate (end product of fermentation) or amino acids (Glutamate, glutamine, and alanine) via gluconeogenesis in the liver.
Ruminants typically have much lower
blood glucose concentrations than non-ruminants.
The primary pathway of glucose metabolism is
glycolysis and the TCA cycle. This occurs when there is an energy demand. The process yields 36 ATP and there is 7.3 kcal/mole of ATP. There are 673 kcal/mole of glucose. Therefore, the process is 39% efficient ([36 x 7.3] / 673). The rest of the energy in glucose is lost as heat during metabolism.
When caloric intake exceeds requirements for maintenance and production
glucose carbon can be converted to fat
Ways glucose carbon can be converted to fat due to caloric intake exceed
1)Glucose can be converted to glycerol 3-P. This serves as the "carbon backbone" to which fatty acids are esterified to during synthesis of triglycerides.
2) Glucose can be converted to fatty acids. Glucose can be converted through a multiple step process to pyruvate, which in turn can be converted to acetyl-CoA, the building block for fatty acid synthesis
Glycerol + 3 FA
The conversion of glucose to fatty acids is
irreversible. There is no net conversion of fatty acid to glucose.
Fatty acid oxidation (breakdown) yields
acetyl-CoA, however, it cannot be converted to glucose.
Although acetyl-CoA can enter the TCA cycle
there are two CO2 generated in the pathway to glucose synthesis. Consequently the two carbons present in the acetyl-CoA molecule resulting form fatty acid oxidation are lost and there is no net flow of carbon to glucose.
fatty acid synthesis (also called lipogenesis) requires the cofactor
NADPH. NADPH can be generated via glucose metabolism through the pentose shunt.
glucose roles in lipid synthesis are
1. Glycerol Synthesis 2. FA synthesis 3. NADPH supply
If the animal is being fed energy in excess of its requirements
glucose can be stored as glycogen, primarily in liver and muscle. However, the amount of energy that can be stored in this manner is limited.
Conversion of fat and storage of fat takes place
when capacity for glycogen storage has been exceeded.
Muscle stores glycogen for its own use, whereas the liver
can hydrolyze the glycogen and export the glucose to other tissues.
Liver glycogen mobilization in nonruminants typically occurs
between meals. There is less fluctuation in liver glycogen in ruminants because in contrast to most non-ruminants, they have a more continuous flow of digesta from the rumen to the small intestine.
Various intermediates of glucose metabolism can be used for the
synthesis of amino acids (e.g. pyruvate, glycerol-P, alpha-ketoglutarate)
When oxygen becomes limiting (e.g. horse racing)
lactate rather than C02 and H2 0 is the primary end product of glycolysis in muscle. Lactate can diffuse into blood and be transported to the liver.
Pain in muscles during exercise= lactate
The liver can convert
lactate to glucose. This glucose can re-enter the blood and be transported to muscle. The net cost is 4 ATP for every 2 moles of lactate that are converted to glucose. The ATP for this comes primarily from the oxidation of fatty acids in the liver. This process is referred to as the Cori cycle
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