Midterm Material Flashcards

Question

Pancreas

Answer 1

• Endocrine function (produce hormones which is released into the blood stream) – Produces hormones, insulin and glucagon for regulation of blood glucose • Exocrine function (produce a substance which is secreted out through a duct) – Major digestive enzymes for carbohydrates, lipids, proteins, nucleic acids – Sodium bicarbonate to neutralize stomach acids, stop action of pepsin, and increase pH in small intestine: Why is this important? – Pancreatic duct enters proximal duodenum

Answer 2

Largest gland in body (1 to 2% of BW); in contact with diaphragm • First organ or gland to process blood coming from GIT via portal vein carry products of absorption • Metabolic powerhouse of the body – CHO metabolism • Converts glucose to glycogen and TG (triglycerides) • Breakdown glycogen into glucose • Converts AA (amino acids), LA (lactic acid), and C3 (propionate) into glucose • Metabolic powerhouse of the body – Protein metabolism • Deaminate AA for use in ATP synthesis • Convert AA to CHO and fats • Synthesize plasma proteins (albumin, prothrombin, fibrinogen) • Metabolic powerhouse of the body – Lipid metabolism • Hepatocytes can store TG • Use FA to make ATP • Synthesize Lipoproteins and cholesterol • Cholesterol used to make bile salts –Detoxification •Detoxifies alcohol and AB •Detoxify NH3, converting it to urea –Synthesize bile salts which are used to emulsify lipids in the s.i. –Storage of fat soluble vitamins (A, D, E, and K) and B12, Fe, Cu, and glycogen • Metabolic powerhouse of the body –Helps in the activation of active form of Vitamin D •Converts cholcalciferol into 25 hydroxycholcalciferol •Kidney converts 25 hydroxycholcalciferol into 1,25 dihydroxycholcalciferol which acts on intestinal cells to increase Ca absorption •Includes largest part of macrophage system with the presence of Kupffer cells which remove foreign materials that enter the blood from the stomach and intestines – Kupffer cells also remove tissue debris such as old and fragile RBC (erythrocytes).

Answer 3

• Found in all domestic animals except the horse • Used to store bile which is needed for fat digestion – Emulsifies lipids to enhance action of pancreatic lipase – Bile enters proximal duodenum via common bile duct near where pancreatic duct enters

Answer 4

• Excrete metabolic byproducts/toxins • Reabsorption – Urea, etc. • Acid/Base balance

Answer 5

``` • Ingestion • Ruminal Fermentation – VFA absorption – Microbial protein synthesis • Intestinal digestion – Nutrient absorption – Fecal excretion • Liver Metabolism • Incorporation into tissue • Urinary excretion ```

Answer 6

- constant supply of nutrients - water - continuous removal of products of digestion/fermentation (gases, VFA's, NH3 - Regulation of PH to prevent acidosis (problems if this doesn't occur)

Answer 7

``` Substrate availability/Ruminal Volume – Feed fermented to volatile fatty acids “VFA” – Passage and absorption – no build-up of non-digestible substrate for the most part – Microbial biomass produced • Temperature – 38 - 42C • Regulated pH – Saliva – VFA absorption (passive) • Oxygen limiting – Anaerobic; does this mean there is no O2 in the rumen? ```

Answer 8

``` • Symbiotic relationship – With each other – With the host • Bacteria – 109 – 1012/g – > 200 species – Can be strict anaerobes or facultative anaerobes • Protozoa – 103 – 106/g • Anaerobic Fungi ```

Answer 9

• Major contributor to microbial fermentation – One of major focuses in ration fermentation for high and low producing animals is to ensure the nutrient requirements of the microbes are met • Most dynamic population with large diversity of species and activities • Symbiotic relationship with each other – Crossfeeding – Cellulolytic bacteria (fiber digesters) outnumbered by noncellulolytic (digest starch & sugars) yet the latter benefit from the actions of the cellulolytics • Most extensively studied, yet much yet to learn

Answer 10

• Fibrolytic – Cellulolytic • Cellulose – Hemicellulytic • Hemicellulose (HC) – What is the difference between cellulose & HC? • Cellulose made up of β 1-4 glucose linked polymer • Hemicellulose is a heterogenous collection of polysaccharides which can be β 1-2, 1-3, and 1-4 linked polymers – Xylan – Arabinose – Uronic acid • Hemicellulose more closely bound to lignin than cellulose

Answer 11

• Not a CHO but a polyphenolic compound • Protects the plant – Chemical + biological (disease) resistance – Provides mechanical strength • Only binds to hemicellulose • Found in stems rather than in leaves • Concentration in plants influenced by: • Maturity • Ambient temp: Hi temps increases lignin synthesis Major factor limiting digestion of forage cell walls • Physically encrusts fiber • Protects cell wall CHO from attack • Alters stereochemistry of plant CHO • May be toxic to specific cellulolytic bacteria • Which chemical analysis or analyses will we find lignin?

Answer 12

``` • Fibrobacter succinogenes: Most common cellulolytic bacterium • Butyrivibrio fibrisolvens • Ruminococcus albus • Ruminococcus flavefaciens • Prevotella ruminicola – Digests plant cell wall polysaccharides (ie. xylans and pectins) but not cellulose • Succinivibrio dextrinosolvens: Ferments hemicellulose and pectin • Ruminococcus sp. – Degrade fibre – Colonize plant tissues ```

Answer 13

``` • Keep CO2 and hydrogen low • Interspecies hydrogen transfer • Produce methane • Compete with acetogens (use CO2 for acetate production) • Target of extensive research: Why ? • Methanogens – Methanobacterium formicicum – Metanobrevibacter ruminantium – ETC ```

Answer 14

• Butyrivibrio fibrisolvens • Streptococcus bovis: capable of rapid growth – Plays role in lactic acidosis development • Ruminobacter amylophilus: usually in low numbers but is a major starch digester • Prevotella ruminicola: makes up 60% of total rumen bacteria • Selenomonas ruminantium: found in high numbers on cereal grains • ETC!!!

Answer 15

``` – Lactobacillus: ferments sugars to produce lactate • Role in lactic acidosis – Prevotella ruminicola – Butyrivibrio fibrisolvens – ETC • Acid Utilizers – Selenomonas ruminanium – Veillonella alcalenscens – Megasphaera elsdenii – ETC ```

Answer 16

– Selenomonas ruminanium – Veillonella alcalenscens – Megasphaera elsdenii – ETC

Answer 17

* Butyrivibrio fibrisolvens * Prevotella ruminicola * Ruminobacter amylophilus * Selenomonas ruminantium * ETC!!!

Answer 18

``` • Anaerobic, Approximately 104/ml • Much lower numbers than rumen bacteria • Vary considerably with feed type • May contribute up to 40% of ruminal microbial N • Role in Soluble CHO fermentation • Engulfment and digestion of bacteria – Two groups: • Entodiniomorphids • Vestibuliferids ```

Answer 19

 Engulf particles or other protozoa/bacteria  Digest starch, cellulose, hemicellulose  Entodinium  Epidinium  Ophryoscolex  Polyplastron

Answer 20

``` • Approximately 20% of protozoa in rumen • Numbers increase before feeding • Non-structural polysaccharide and soluble sugar digestion • Colonize plant tissue • Consume bacteria • Isotricha • Dasytricha ```

Answer 21

``` • Neoallimastix, Caecomyces, Pyromyces, Orpinomyces, Anaeromyces • <8% of total microbial mass • Access and colonize plant tissue • Greater with increased fibre, longer forages • Cellulolytic activity • May contribute up to 30-40% of ruminal fibre digestion • Certain species can digest lignin • Proteolytic ```

Answer 22

Alpha glucose linked polymer: animal enzymes can digest if it is available to the animal enzyme Beta glucose linked polymer: digested by microbial fermentation In lectures, often will refer to alpha-linked and betalinked glucose polymers

Answer 23

``` • NDR or NDF: Hemicellulose Cellulose Lignin Some Protein Bound N Minerals Cuticle Hemicellulose and Cellulose are beta glucose linked polymers • ND Solubles = Cell contents Sugars Starch Lipids Fructans Pectin Beta Glucans Proteins Which of the CHO here are alpha vs. beta linked polymers? ```

Answer 24

``` • 100 - %NDF in feed = Cell contents Cell contents fraction will be completely available to microorganisms (pregastric and hindgut) Cell contents less pectin and beta glucans will be completely available to animal enzymes ```

Answer 25

• Fibre (definition can be vague) – High in forages or roughages (hay, pasture, silage) – Not digested by mammalian enzymes – Cell wall components or structural CHO in plants – NDF, ADF • Hemicellulose • Cellulose • Lignin (mostly not digested) – What about soluble fibres? What do they include? • Pectin: rich in galacturonic acid – α 1-4 linked polymers – Fermented and not digested by animal enzymes • β glucans – β 1-3 and β 1-4 linkages – Fermented and not digested by animal enzymes • Sugars – In byproducts such as molasses • Starch – High in grains: grain to grain variation; relate the amount of starch to which nutrient value? • 47% to 95% digested in R-R • Action of alpha-amylases (extracellular enzyme) – Found in cell-free rumen fluid but 70% associated with particulate-bound microorganisms • Both bacteria and protozoa will engulf CHO and contain storage polysaccharide

Answer 26

• Approximately 90% occurs in R-R • 2 step process – Microbial attachment – Hydrolysis • Lag period (delay) in digestion as: – Substrate must be exposed: how does that happen? – Bacteria must get to the fiber (slow process) – Feed particle must be wet (in 3120, how did you prep your bags before incubation?) – Bacteria must attach to the fiber – Bacteria need to use extracellular enzymes

Answer 27

• The fraction of the feed that stimulates chewing activity • Chemical & Physical characteristics • Particle size • Effect on rumen pH & fiber digestion • Feed composition guides will often state the eNDF content

Answer 28

• Why do rumen microbes make volatile fatty acids (VFA)? – Anaerobic pathways to provide ATP for microbes • Sometimes called Short Chain Fatty Acid (SCFA) – 2 – 5 Carbons in length • Acetate, Propionate, Butyrate, Isobutyrate, Valerate, Isovalerate – Absorbed in rumen and anywhere else? – Metabolized, used as energy source, precursor for other molecules, signal for metabolic activity?, tissue health – 50-85% of metabolizable energy comes from VFA • Forage diet

Answer 29

``` Key points on this slide: 1) Microbes are converting BOTH α- and β-linked CHO into hexoses 2) Hexoses are being converted to pyruvate which is a central intermediate in rumen bacterial metabolism 3) What about pentoses? ```

Answer 30

• Carbohydrate breakdown products (glucose, etc.) are the primary precursors for Acetate, Propionate, and Butyrate – Relative proportion of VFA dependent on microbial populations which are dependent on substrate, etc. • Where is this substrate coming from? – What about VFA production from AA? • Protein breakdown products precursors of Isobutyrate, Valerate, and Isovalerate – Fermentation products of valine, proline, and leucine – Valerate also minor product of CHO fermentation – May also stimulate growth of fibrolytic bacteria • 3 primary cellulolytic species can not synthesize BC AA unless they have BC VFA available as substrates

Answer 31

``` • F/C ratio: high concentrates C2, CH4 while C3 • Buffers: C3, while C2 and CH4 • Decreasing PS: C2, CH4 while C3 • Ionophores: C2, CH4 while C3 • USFA: CH4 while C3 ```

Answer 32

``` • More propionate increases energy (and potentially glucose) available to animal – Decrease energy lost as methane • High concentrate diet? • Ionophores – Inhibit H producing bacteria such as Ruminococcus & Butyvibrio • Reduce growth of methane producers – Promotes C3 production • Milk fat? ```

Answer 33

• Butyrate and tissue growth and health – Inhibits inflammation and carcinogenesis, increases colonic defence barrier/decreases intestinal permeability, and oxidative stress (Hamer et al. 2008) • Signal metabolic activity – May influence insulin and glucagon secretion (Bergman 1990) – May influence pancreatic exocrine secretion (Katoh, 1989) – May be receptors located in GIT that could influence motility, GI hormone production, etc. (Tazoe et al 2008)

Answer 34

``` • Lactate – Is this product usually important? metabolized to c2 and c3 • Methane – Large amounts of H2 produced in rumen but methanogens use it to produce CH4 • Heat of fermentation ```

Answer 35

``` •Passive transport •Also likely facilitated transport •pH influences absorption •↓ pH ↑ absorption •Free acids> anion form of the acid •Efficient absorption from GIT still occurs at normal rumen pH (approx 6 - 7) but may occur in abomasum •Differences in opinion on order of absorption •Chain length: C4 > C3 > C2 •Epithelial cell metabolism •Amounts produced: C2> C3 > C4 ```

Answer 36

• Acetate - oxidized as energy source and precursor for fat synthesis • Propionate – oxidized as energy source and precursor for glucose production • Butyrate – oxidized as energy source and converted to ketone bodies (Beta hydroxubutyrate)

Answer 37

* Used by peripheral tissues as energy source or FA precursor * Main precursor for lipogenesis in ruminants * What is the main source in nonruminants?

Answer 38

• Variety of colored salts for food animal production species – White: plain NaCl Red: Iodized salt – Brown: TM salt Blue: Co-Iodized salt

Answer 39

• Species differences – Nonruminant: 80 to 120 mg/ 100 ml plasma – Ruminant: 60 to 80 mg/ 100 ml plasma • Can handle levels as low as 40 mg/ 100 ml plasma – Why the differences • Where does blood glucose come from? – Nonruminant: predominant source would be ? – Ruminant: • Glucose absorbed from GIT; is this important? • C3 • Glycerol from ? • AA (especially ASP, ALA, GLN)

Answer 40

* Diet Composition & Particle Size * Intake * Passage Rate * Rumen pH * Others ?

Answer 41

• Diet Composition & Particle Size – Intake of cell contents vs. NDF – Presence of heat damage – Call microbial enzymes access nutrients (function of particle size & integrity) – Large PS require ??? to increase access to microbes – Small PS: particles escape R-R before ? • Intake (speed up R of P which limits RRT) • Passage Rate • Rumen pH: affected by Intake of cell contents vs. NDF which will impact digestion of ? • Others ?

Answer 42

• Ranges from 5.5 to 7 usually unless there is a problem • Different bacteria have different pH optimums – Why is this important for feedstuff utilization? • CHO: Low pH affects digestion of ? • NPN: high pH allows ammonia to leave the R-R – Impact on utilization of ammonia in the R-R? • Low pH – Lactate producers – “Lactic Acidosis” High pH: more cellulolytic activity and C2 production Low pH: more amylolytic activity and C3 and lactic acid production

Answer 43

– Presence of rumen mat: site of partially digested, long fiber particles that get tangled amongst themselves as too large of a particle size to leave R-R – Mat formed by contractions of R-R which mixes recently ingested feed with mat – Microbial fermentation occurs here releasing gasses which get trapped in mat which makes the mat buoyant

Answer 44

Feed particles stay in mat until physical and(or) chemical digestion reduces the particle size such that they fall thru mat into the ventral rumen – Mat may also contain concentrate particles which get trapped in the mat • Presence of the mat – Stimulates increases retention of articles in R-R and increases feed utilization – Stimulates rumination which leads to more saliva flow, increased amounts of buffers entering rumen, and better control of pH • Integrity of mat affected by: – Particle size of forages fed • Grinding, pelleting, chopping, or over-mixing reduces PS which leads to mat breaking up – Affects rumination, saliva production, and pH • Feeding of high concentrate /low roughage diets will lead to essentially no ruminal mat present – Affects rumination, saliva production, and pH and the predisposition to acidosis

Answer 45

``` • A sequence of amino acids connected by peptide bonds • Contain Carbon, Hydrogen, Oxygen and Nitrogen – Some contain Sulfur and phosphorus • Amino acids precursors of body protein – Main component of muscle • Also can be oxidized for an energy source or converted to other molecules such as glucose (gluconeogenesis) ```

Answer 46

• In general, feedstuffs made up of high MW compounds including CHO, proteins, and lipids – Most microbes can not directly use these compounds • Must be broken down into lower MW compounds such as sugars, oligosaccharides, peptides, AA before they are of value – Extracellular microbial enzymes can now handle these compounds • All 3 microbe classes can digest proteins – Bacteria are most important – Protozoa are headhunters of bacteria

Answer 47

• Feeds differ in the degradability of protein – Rumen degradable protein (RDP) or Degradable Intake Protein (DIP) – Rumen undegradable protein (RUP) or Undegradable Intake Protein (UIP) bypass protein – Heat damaged protein • Microbes contain enzymes which break down DIP to peptides, amino acids, and ammonia • Feeding urea (NPN)? – Providing a source of N for ?

Answer 48

• Not all of the breakdown products from fermentation of DIP are used by all bacteria – Many rumen bacteria utilize ammonia as a source of N – Some bacteria require amino N in the form of amino acids or peptides as a source of N • Free AA catabolized quickly into NH3, C2, C3, isobutyric acid (from valine), isovaleric acid (from leucine) and 2-methyl-butyric acid (from isoleucine)

Answer 49

``` • Incorporate ammonia, amino acids, peptides into bacterial protein • Amounts of fermentable carbohydrates influences bacterial protein synthesis – How? – Which CHO better promote MP synthesis? ```

Answer 50

``` • Large Hydrophobic molecules • Often found as mono-, di-, or triglycerides – Fatty acid(s) bound to glycerol backbone • Fats are biohydrogenated in the rumen – Reduce double-bonds to make more saturated – Lipids flowing to small intestine are more saturated than in non-ruminants ```

Answer 51

• Why is fat added to diets? • Problem is that added fat of more than 8% of the diet DM can decrease rumen fermentation – Coating of fiber & other feed components – Inhibits microbial activities • Poly-Unsaturated fatty acids are more toxic although also may be beneficial as a H sink thus reducing CH4 production – Fat inhibits bacteria that produce H » Decrease acetate/propionate ratio – Fat has major effect on fibrolytic bacteria

Answer 52

• Extensive lipolysis to free fatty acids – By bacteria and protozoa • Hydrogenation of free fatty acids – Slower rate than lipolysis, but few polyunsaturated fatty acids present in rumen – Detoxification rxn to get rid of double bonds • Bacteria incorporate fatty acids into cells and also synthesize fatty acids • May be some absorption and breakdown of fatty acids by rumen epithelia but is thought to be minimal

Answer 53

• Lipids will leave the ruminant stomach as free fatty acids, bacterial lipids, and bypass lipids for intestinal digestion & absorption • Composition of fatty acids flowing to small intestine quite different than dietary fatty acids due to hydrogenation

Answer 54

• Plant based feedstuffs will almost always contain: – CHO – Protein – Lipids – Vitamins & Minerals – Feedstuffs may also contain anitiquality components or antinutritional factors that may affect nutrient availability or cause problems – The question is how do all of these contribute quantitatively & qualitatively for balancing the intended ration • Can we make the same claim for animal-based feedstuffs in regards to nutrient composition and the presence of antiquality components (antinutritional factors)? – Are all of these nutrients found in animal-based feedstuffs? – One can find NDF values for meat meals. How is that possible?

Answer 55

• The summation of processes by which macromolecules in food are degraded to simpler compounds which are absorbed from the gastrointestinal tract. • Apparent digestibility (%) = {[nutrient consumed (g/d) – nutrient excreted in feces (g/d)] / nutrient consumed (g/d)} * 100 – [(In-Out)/In] * 100 – Total tract vs specific segments of GI tract – Why do we call it apparent digestibility?

Answer 56

``` • Similar to monogastrics • Starch, Protein, Lipid, and Nucleic Acids • What happens to fiber in small intestine? ```

Answer 57

``` • Heterogeneous polysaccharide composed of amylose and amylopectin • Glucose polymer which contains -1,4 and -1,6 linkages – How does this compare to cellulose? • Storage form of carbohydrate in seeds • High concentrations in grains • Dietary energy source – Primary source of energy in feedlot diets ```

Answer 58

``` • -Amylase – Secreted by pancreas • Maltase & Isomaltase – Small Intestinal brush border • Sodium dependent glucose transporter (SGLT1) – Small Intestinal brush border ```

Answer 59

``` Hexoses, glucose, galactose, and fructose can not diffuse across cellular membranes by themselves. Need help of transporter proteins for entry or exit into cells. SGLT1: transporter for glucose to cross into blood. Na dept. transporter which couples glucose transport to an inwardly directed Na gradient maintained by Na+ K+ ATPase ``` ``` GLUT2, another transporter which serves as the major transport process for absorption of glucose from the intestinal lumen ```

Answer 60

``` • Limited -amylase, maltase, or isomaltase activity • Limited glucose absorption • Insufficient time for complete starch hydrolysis (fast Rate of Passage from the small intestine) • Inadequate access of enzymes ```

Answer 61

``` • HCl & Pepsin – Secreted by abomasum – Initiates post-ruminal digestion • Trypsin, Chymotrypsin, Elastase, Carboxypeptidase – Secreted by pancreas into small intestine • Small Intestinal Brush Border Peptidases – Endopeptidase, Aminopeptidase, Carboxypeptidase, Dipeptidase • Peptide, Amino Acid Transport ```

Answer 62

``` Peptide and AA transport similar to glucose in that it involves Na ions for cotransport. Some AA do not require the Na co-transport mechanism ```

Answer 63

``` • Peptide transporters – PepT1, PepT2 • AA transporters – Anionic • EAATs, xCT – Cationic • CATs – Neutral • GlnT, ATAs, ASCTs, LATs – Neutral & Cationic • ATB0+, BAT1 ```

Answer 64

``` • Large Hydrophobic molecules • Fats are biohydrogenated in the rumen – Reduce double-bonds to make more saturated – Lipids flowing to small intestine are more saturated than in non-ruminants ```

Answer 65

• Salivary Lipase? – Limited importance for adult ruminants but more important for newborn ruminants • Abomasal Lipase? – Can attack emulsified fat and convert it to FA and glycerol. However most fat entering abomasum is not emulsified so little action there • Bile – Emulsifies lipids and forms lipid droplets • Pancreatic Colipase & Lipase – Colipase displaces bile acids – Lipase cleaves fatty acids • Absorption of fatty acids by diffusion

Answer 66

1. Stage of Growth 2. Size of Animal 3. Environment 4. Genetics 5. Disease 6. Activity (in drylot or on pasture as examples) 7. Condition of Animal - How much fat? 8. Ration Imbalances - Nutrient Ratios 9. Species/ Breed Differences /Sex –MANY OTHERS!

Answer 67

``` • A subcommittee of North American Scientists is formed to update requirements every few years depending on advancements in the field • 1st NRC to include computer model to predict requirements and performance of several classes of beef cattle ```

Answer 68

``` • Determine nutrient requirements for various classes of beef cattle – Cattle types (think of the variation) – Body sizes (think of the variation) – Milk production levels – Environmental conditions • Predict animal production – Energy and protein deposition – Examine diets for economic and environmental benefits ```

Answer 69

``` • Improve nutrient management via animal feeding – Minimize Overfeeding – Increase Efficiency – Maximize Performance – Reduce Nutrient excretion – Reduce Methane production – Reduce Manure production • How do the above affect dollars going back into the producer’s pockets? • Improve nutrient management via animal feeding – Overfeeding – Efficiency – Performance – Nutrient excretion – Methane production – Manure production • How do the above affect dollars going back into the producer’s pockets? ```

Answer 70

``` • Cost of production – Feed costs: 50 - 80% of production costs in feeding operations – Manure disposal: up to $20 per animal • Environmental concern – N, P – Methane – Odor ```

Answer 71

• Level 1 – Empirical (based on observation and experience) – Higher in predictive accuracy – Simpler to use – CowBytes based on level 1 • Level 2 – Mechanistic – Increases information about digestion and passage rates for CHO and N – Incorporates information about amino acids – Developed to increase understanding of process

Answer 72

• Responsibility of User: Accurately define animals, feeds, and environmental conditions • Nutrient requirements can change relative to the specific diet fed – Dynamic: we are going to see continuous change as we learn more and more about digestion, metabolism, physiology, & behavior – Older versions of the requirements were discrete & could easily be looked up in tables

Answer 73

``` • The potential to perform work • Energy is not a nutrient – Provided by which nutrients? – Role of other nutrients? • Units – calorie = the heat required to raise the temp of 1 g of water from 16.5 to 17.5C • Kcal (Cal), Mcal • 1 calorie = 4.184 joules • 1 joule = 1 newton per metre ```

Answer 74

``` 1. Feed quantity/quality – How much is offered? – Nutrient content and balance – Digestibility 2. Animal Characteristics – Feed Intake Regulation • Dependent on dietary and non-dietary factors • Fill, energy density • Behavior, environment – Social hierarchy: Round bale feeder feeder or roll the bales out? – Size – Animal Genetics • Potential to utilize energy – Animal Physiological State • Potential to utilize energy 3. Environment – Temperature, wind, humidity, etc. – Housing ```

Answer 75

* Physiological Fuel Value System * TDN: Total Digestible Nutrients * DE: Digestible Energy * ME: Metabolizable Energy * NE: Net Energy

Answer 76

• Carbohydrate 4 kcal/g • Fat 9 kcal/g • Protein 4 kcal/g • Used in human and lab animal guidelines • These are estimates which can vary greatly depending on source of nutrient • Ruminant?

Answer 77

• TDN: measure of relative energy value of a feed (in tables as a %) • Sum of digestible CP, CF, NFE plus (digestible EE x 2.25) • What is missing here ? • Need digestion coefficients to do this” • Does not include energy losses from urine, fermentation, gases, heat losses • Useful because of a long history of using this system but not as accurate as other systems

Answer 78

``` • Gross energy (GE) – Heat of combustion • Digestible energy (DE) – DE = GE - fecal energy (FE) • Metabolizable energy (ME) – ME = DE - (urinary energy And combustible gas losses) • Net energy (NE) – NE = ME - heat increment • Maintenance • Production ```

Answer 79

``` • GE = gross energy Total heat of combustion (kcal) • Determined using bomb calorimeter What do we know about the availability of that energy? • CHO: grain versus straw • Fat vs carbohydrate • Is it really that simple with ruminants? • Rumen vs. S.I. availability • Physical form of the feed • Starch by fibre interactions • FE = fecal energy Undigested food, microbial cells, & endogenous losses ```

Answer 80

``` • DE = GE – FE The portion of the GE in a feed that is not excreted in feces • Reflects diet digestibility • Does not accurately assess all diets Overestimates value of high-forage diets (Why?) Doesn’t account for several major losses of energy associated with digestion & metabolism of food • 1 kg TDN = 4.4 Mcal DE (approximately) ```

Answer 81

``` • ME = DE – (GAS Energy + Urine Energy) • A measure of the dietary energy available for metabolism • Going one step further than DE and taking into account urinary and gaseous losses, ME provides a more satisfactory measure of nutritive value than do TDN or DE. • Ratio of ME to DE = .8 (average) Dependent on DMI, rates of digestion &passage, age, feed source ``` • Urinary losses • N compounds (urea, creatinine, allantoin, etc.) • How are these important for beef cattle? • Non-N compounds: citric acid & glucuronic acid • Gaseous losses • Methane – CH4 • On average, 8% of total energy intake. • Methane contains 13.34 Kcal per gram. • Ruminants gaseous losses are larger than urinary losses • Gaseous losses of energy are greater on roughages than concentrates

Answer 82

• NE = ME - HI • A certain portion of the feed energy is lost as heat related to ingestion and digestion. After accounting for this portion, one arrives at the portion which is completely useful to the body -- NET ENERGY. • NE is the portion available for sustenance of life and productive purposes. • Preferred method for measuring energy nutritive value for ruminants ``` • NE = ME - HI HI = Heat increment • Includes Heat of fermentation Heat from nutrient metabolism »Varies with feeds + nutrients »Voluntary activity, thermal regulation, and product formation if you agree with Ferrell & Oltjen • Can be useful or detrimental • Portion of ME used for maintenance and production: Includes NEm and NEp ```

Answer 83

* Maintenance | * Production

Answer 84

• The amount of feed energy intake that will result in no net loss or gain of energy from the tissues of the animal body In theory, the animal should not be changing weight

Answer 85

``` • Includes NEm and NEp • NEm Basal metabolism Voluntary activity for maintenance Heat to warm or cool body • NEp (NEg the main one for beef cattle) Work Tissue gain Product synthesis ``` ``` • Most precise measure of feed nutritive value for energy Animal requirements independent of the diet (may be a good thing?) Estimate energy requirements for different physiological functions • NEm • NEg • NEl – In beef cattle, efficiency of ME use for lactation similar as for maintenance so express both as NEm ```

Answer 86

• NEm requirements of beef cattle 0.077 Mcal/EBW.75 • EBW = kg empty body weight • General equation, adjustments then made • What does this mean? For unit EBW.75, NEm requirements will be similar but heavier animals are going to need more energy than lighter animals ``` • NEm requirements of beef cattle Not constant varies with • BW • Genotype • Sex • Age • Temperature • Physiological state • Previous nutrition Compensatory Growth ```

Answer 87

• Bos Indicus breeds (eg Brahman, etc.) require about 10% less energy for maintenance than beef breeds of Bos taurus cattle (eg angus, hereford, charolais, limousin) • Dairy or dual-purpose breeds of Bos taurus cattle (eg Simmental, Holstein) require about 20 percent more energy than beef breeds • Suggested there is a positive relationship between maintenance requirements and genetic potential for measures of productivity (rate of growth or milk production)

Answer 88

``` • Maintenance requirements for bulls are 15% higher than that of steers or heifers of the same genotype • Age effects less clear although it seems that maintenance requirements decrease with age in most species – NRC & Cowbytes do not take age into account for estimating maintenance requirements ```

Answer 89

• Thermoneutral zone: heat production dependent on feed intake and efficiency of feed utilization – Body temperature affected primarily by regulation of heat dissipation • Upper Critical Temperature – Feed intake decreases – Maintenance requirements increase - Increased respiration and metabolic rates to get rid of heat • Lower Critical Temperature – Feed intake increases – Maintenance requirements increase - Increased requirement to maintain body temp by increasing heat Previous Temperature (Acclimation) – Adaptive changes that the animal follows in response to changes in climatic conditions • Utilizing terrain, fellow animals, modifying own behavior – Huddling in groups or by windbreaks – Shade seeking – Hill seeking for wind exposure – Wading in water to dissipate heat • Cold Stress – surface area & insulation, temp & wind • Heat Stress – Above 30C and animal panting – Increase in maintenance requirement - 7% with rapid shallow panting, 11-25% with deep open-mouth panting

Answer 90

• Lactating vs nonlactating – 20% increase in maintenance requirements – Separate from milk NE – Assume efficiency of use for NEm = NEl • Grazing can increase maintenance requirements by 10 – 20% – Dependent on terrain, forage availability, and forage quality – Other Activity? Weather, water location

Answer 91

``` • Greater than normal feed intakes • Decrease maintenance costs so improve feed conversion • Shrink GIT which uses lots of energy • Decrease metabolic rate • Lower costs of production • Ideal is to have similar time on feed as conventional finishing ``` ``` • Dependent on length and severity of restriction – Restricting vs stunting growth • A general estimate is that restricted feeding reduces maintenance requirements by approx. 20% during restriction and for 60 – 90 days of compensation – High variation - dependent on length & severity of restriction – Why? ```

Answer 92

• Pasture or range cattle will lose weight when forage resources are limiting – Limited quantity & often lower quality • Efficiency of use of this energy differs dependent on body condition – Protein vs fat • More energy from fat vs. lean cows as muscle will be mobilized in the latter • Approximately 80% efficiency of use of energy from body tissue loss for maintenance or milk production

Answer 93

``` NEg requirements of beef cattle The amount of energy deposited as nonfat organic matter (mostly protein) plus that deposited as fat. • Fat contains 9.367 kcal/g and nonfat organic matter contains about 5.686 kcal/g Takes more energy to deposit fat but less energy to maintain fat than protein Dependent on intake of energy above maintenance, impetus to grow (genetics, sex, etc), stage of growth (lean vs fat deposition) ```

Answer 94

• Use feed for NEm and then NEg • 250 kg steer fed 5 kg of a diet containing 1.9 Mcal/kg NEm and 1.4 Mcal/kg NEg. • NEm required = 4.84 Mcal • 4.84 Mcal / (1.9 Mcal/kg) = 2.5 kg feed • 2.5 kg feed * (1.4 Mcal/kg) = 3.5 Mcal • 3.5 Mcal then can be used for growth • Look on 1984 NRC table (next slide) to predict average daily gain possible with 3.5 Mcal – depending on animal type, etc.

Answer 95

• Feed energy cannot be determined using standard analytical techniques of the feed • Calorimetry experiments • Estimation from feed analysis – Estimation of TDN • Based on digestible CP, CF, NFE plus (digestible EE x 2.25) – Must know digestibility • Based on models of feed composition – Eg. (NDF, lignin, CP, ash, EE, acid detergent insoluble fiber, and neutral detergent insoluble fiber) - Weiss et al., 1992 – Conversion of feed TDN values to NE values based on relationship between TDN and NE as determined through calorimetry

Answer 96

``` 1 kg TDN = 4.4 Mcal DE 1 lb TDN = 2.0 Mcal DE ME= DE times 0.82 NEm = 1.37ME –0.138ME^2+0.0105ME^3 -1.12 NEg = 1.427ME –0.174ME^2+0.0122ME^3 -1.65 ```

Answer 97

``` • Balance studies – Digestion (Fecal Energy) – Urinary energy • Calorimetry – Direct – measure heat production • Estimate fasting heat production = maintenance requirement – Indirect – measure oxygen consumption • Comparative Slaughter – Body energy content – Body composition ```

Answer 98

• Limitations – Feed values difficult to predict from typical analysis – Additive effects only (i.e. depending on other ingredients, nutrient flow, digestion and metabolism could change resulting in differing NE values for that feed) – Energy system does not account for differences in site of digestion • What Next? – Nutrient-based system rather than energy-based system

Answer 99

• Fermentation in the rumen results in heat production and methane losses • Difficult to predict post ruminal carbohydrate flow – Dynamic system – NRC level 2 begins to examine the dynamics of digestion

Answer 100

``` • Energy sources are broken down further based on chemical + physical properties CHO • Nonfiber CHO (NFC) Sugars Starch • Fiber Available and Unavailable fiber »NDF, lignin, NDIP ```

Answer 101

``` Rates of ruminal digestion – CHO • A (sugar) • B1 (starch) • B2 (available fiber) – How to determine? • Passage rate to estimate nutrient flow – % forage and eNDF used to calc passage rate ```

Answer 102

``` • Visceral tissue (gut, liver, heart, lungs, pancreas, mesenteric fat, etc.) – 6 – 10% of BW – 40 – 50% of oxygen consumption • Gastrointestinal tract – 20 – 25% of oxygen consumption • Skeletal Muscle – Approx 40% of empty body weight – Approx 21% of energy use – What is responsible for the low energy use for muscle? ```

Answer 103

``` • Epithelial cell turnover (small intestine) • Na+,K+ ATPase – Nutrient transport • Protein synthesis & turnover – Digestive enzymes – Structural proteins • Nucleic acid synthesis – Cell proliferation ```

Answer 104

• Net nutrient flux across tissues – Placement of catheters in blood vessels feeding and draining visceral tissues – Measure net nutrient use of nutrients and oxygen • In vitro approaches – Oxygen consumption – Ion transport, protein synthesis, etc.

Answer 105

• Do we want some energy sources to bypass nutrient digestion? –CHO – Lipids • Limitations of lipid digestion in the R-R • Potential to increase energy supply to the ruminant • Potential to alter fatty acid composition

Answer 106

• Crude Protein (CP) = N * 6.25 • Ruminally Degradable Intake Protein (DIP) = portion of CP degraded in the rumen • Ruminally Undegradable Intake Protein (UIP) = portion of CP not degraded in the rumen and thus available for post-ruminal digestion. • Microbial Crude Protein (MCP) = Protein produced by the microbes in the rumen • Metabolizable Protein (MP, absorbable protein) = that protein that is digested and absorbed by the animal (Includes digested MCP and UIP).

Midterm Material Flashcards

(135 cards)