Term
What are major VFA components from microbial fermentation of cellulose and
hemicellulose in rumen and the large intestine? |
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Definition
Cellulose: Acet, Prop, But
Hemicellulose: Bute, some acet, very low prop |
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Term
Please briefly discuss the major biological steps of lignocellulose polymer
complex degradation by microbes (primarily bacteria)? |
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Definition
Lignocellulose - cellulose polymer - cellodextrin - D-Glucose - ATP + HI + VFA (mainly acet)
*laccase & lignin peroxidases, cellulases & cellulosome, bacterial uptake
Lignocellulose - hemicellilose - pligomers - hexoses + pentose - ATP + HI + VFA (mainly but)
*laccase & lignin peroxidases, free hemi cellulases, hemi cellulases, bacterial uptake
Also get direct fecal lignin residue |
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Term
What are the major biological and chemical factors limiting the breakdown of
lignin (4) and cellulose in feeds? |
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Definition
-very few types of bacteria carry/express the lignin degradation enzymes (lignin is a limiting factor)
-lignin degradation enzymes only operate in strictle anaerobic conditions (some O2 in rumen still)
-laccase & lignin peroxidases (lig deg enz) are relatively very low in hydrolytic activities
-cross linking limits enzyme accessibility
-unique structure of cellulose & hemi-cellulose slows enzyme digestion vs starch
-tough quasi-crystalline structure prevents enzyme access
-hemicellulose has a tough matrix vs starch |
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Term
Please discuss if we can feed high performance animals such as double
muscle steers, race horses, and high yield lactation cows just on high quality
hay without grain to meet their energy requirements and briefly explain why? |
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Definition
-high producing herbivores have high glucose needs (ATP for biosynthesis, NADPH for other rxns)
-even fermentation of high quality hay does not happen fast enough to produce adequate amounts of acetate (for ATP) & propionate (for glucose prod.)
-acetate is also needed for lipogenesis for milk & body fat
-glucose is needed to synth lactose, brain function, NADPH, glycerol in body/milk fat
-need starches in diet to meet needs of beef steers, lactating cows, race horses etc |
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Term
Please discuss what is the well established factor in assessing if soluble
fibre components have “prebiotic effects” in animal nutrition? |
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Definition
-Gut microbe populations will have large amounts of beneficial bacteria, low/no pathogenic bacteria
-Fibre fermentation will have high butryate production (high prebiotic effects, signalling molecule)
-overall beneficial health effects (esp from viscous soluble fibre) |
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Term
What are the major limiting factors that are currently limiting the effective
utilization of lignocellulose complex in feedstock for both animal nutrition and
biofuel industries? |
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Definition
lignin digestive enzymes laccase & lignin peroxidases are limited, can only operate in anaerobic environment & hydrolytic activity is low, not many bacteria prod these enzymes
cellulase & hemicellulase activities are also low
-limits ability of feedstock to utilize linocellulose complex as a source of energy, as well as ability biofuel industry to produce ethanol |
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Term
Please discuss what are the major metabolic fates of VFA arising from
fermenting NDF components in ruminants and in monogastrics. |
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Definition
Produces acetate, butyrate, propionate (primarily acetate)
-all are used for energy production in the form of ATP
-acetate: lipogenesis (cholesterol & LCFA)
-butyrate: signalling molecule, some lipogenesis
-propionate: gluconeogenesis |
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Term
Please discuss the nutritional biochemical mechanisms of essential roles of
plant cell wall NDF components in lipogenesis in ruminants. |
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Definition
ruminants are deficient in the 2 key enzyme activities of "ATP-citrate lyase" and "malate dehydrogenase" cannot use other substrates such as propionate for lipogenesis
Acetate primarily, some butyrate
-used for synth of long chain fatty acids (lipogenesis) essential to produce milk fat, and for marbling in beef
-also to prod metabolic energy in the form of ATP |
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Term
What are the major nutritional and biological effects that insoluble fibre
components may have on monogastrics (ie. NDF)? |
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Definition
-decrease energy density as microbial fermentation is limited
-increase the bulk of diets & fecal material
-increase water holding capacity
-abrasive, increase mucosal cell turnout (endogenous protein output) |
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Term
What are the major viscous soluble fibre components and what are the major
nutritional and biological effects they may have on monogastrics? (10) |
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Definition
Beta Glucan, Pectin, Guar Gum
-fermentation produces large amounts of But, + Acet & Prop
-readily fermentable, enhance microflora activity in intestines (prebiotic)
-But is effective energy substrate, also acts as signalling molecule to upregulate gene expression for bowel health & colon cancer prevention
-lowers pH of LI to increase mineral absorption (Ca)
-increases water holding capacity & fecal volume
-may decrease microbe prod. of odor-causing volatile compounds in meats, milk & feces
-negative effects on digestion & absorb of protein/AA, sugars
-increases endogenous protein secretions
-lowers glycemic index (good for Type II diabetes control)
-flushes out cholesterol, disrupting entero-hepatic cholesterol circulation & reducing blood cholesterol |
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Term
What are the major non-viscous soluble fibre components and what are the
major nutritional and biological effects they may have on monogastrics? |
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Definition
Inulin, Fructo-oligosaccharides, Resistant Starch
-readily fermentable in gut
-prebiotic effects on gut microflora
-prod lots But, some Acet + Prop
-But is effective energy substrate, also acts as signalling molecule to upregulate gene expression for bowel health & colon cancer prevention
-lowers pH of LI to increase mineral absorption (Ca)
-increases water holding capacity & fecal volume
-may decrease microbe prod. of odor-causing volatile compounds in meats, milk & feces
-negative effects on digestion & absorb of protein/AA, sugars
-no antinutritive effects
-no effects on glucose absorption
-not effective in flushing out cholesterol |
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Term
| Why is it essential to feed high-performance herbivores such as double-muscle steers, race horses, lactation mares, and high-yield lactation cows with rations that have a balanced ratio of high-quality fibre feeds (e.g. hay or corn silage) to concentrates including cereal grains and protein supplements (e.g. corn grain and soybean meal)? |
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Definition
-need high quality protein to meet needs & support protein synthesis for muscle growth & milk proteins
-high quality fiber to provide acetate for lipogenesis, cholesterol & milk fat prod
-grain (starch) to provide propionate for gluconeogenesis (ATP, NADPH, glucose for lactose)
-hay alone would be too slow to support whole body needs |
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Term
Please discuss the roles of bile salts in lipid digestion and lipid digestive
end-product absorption. |
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Definition
-amphipathic molecules
-serves as an emulsification agent in splitting luminal lipid droplets into micelles for increasing lipid digestive surface areas
-help lipid absorption by splitting insoluble hydrophobic end products to form micelles to increase absorptive & transport process across intestinal apical mmb |
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Term
| Discuss the key enzymes involved in triglyceride (TG) digestion and major steps of intestinal TG absorption. |
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Definition
key enzymes: lingual, gastric & pancreatic lipases (mainly pancreatic)
Location: lipoproteins synth in RER, TGs synth & packed in SER, further modification in Golgi
1. TG processed in lumen of upper SI
2. Bile salts secreted into lumen, emulsify TGs so enzymes can be effective
3. LCFA & monoacylglycerides released, transported across apical mmb via putative transporter into cytosol
4. Majority are converted back into TGs, packed into CM, exported to lymph system via exocytosis (bypasses liver) then enter systemic circulation
5. Some are packed into VLDL particles, exported to blood capillary via exocytosis, flow into hepatic vein blood circulation |
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Term
| Please discuss the key enzyme(s) involved in cholesterol ester (CE) digestion and major steps of intestinal cholesterol absorption. |
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Definition
Key enzymes: pancreatic cholesterol esterase, acyl-CoA cholesterol acyltransferase
1. Primarily processed in lumen of upper SI
2. Bile salts secreted to emulsify cholesterol ester & allow cholesterol esterase to act effectively
3. Free cholesterol transported across apical mmb via putative transporter into cytosol
4. Some transported back into gut lumen via ABC cholesterol transporter
5. Majority of free cholesterol converted to chol. esters by acyl-CoA cholesterol acyltransferase in cytosol, packed into CM, exported into lymph capillary via exocytosis to enter systemic circulation
6. Small amount of CE are packed into HDL/VLDL and exported into blood circulation then sytemic circ.
Locn: lipoproteins in RER, cholesterol esters synth & packed in SER, modification in Golgi |
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Term
What are chylomicrons and VLDL and their roles in long-chain fatty acids and
cholesterol absorption? |
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Definition
-blood soluble proteins which serve as transport vehicles for lipid molecules which are insoluble in blood
CM transport TG, PL C & CE from the intestine using proteins Apo B,C,A & E
VLDL transport TG, C, CE coming from the liver using proteins Api B,C & E |
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Term
| Please discuss the key enzyme(s) involved in phospholipid (PL) digestion and major steps of intestinal PL absorption. |
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Definition
Key enzymes: Phospholipase A1 & A
1. Primarily processed in lumen of upper SI
2. Bile salts secrete into lumen, emulsify PLPs for effective digestion by pancreatic PLP A1 & A2
3. Long chain free FAs & lysophospholipids released, transported across apical mmb via putative transporter into cytosol.
4. Majority converted into PLPs, packed into CM & exported into lymph capillary via exocytosis then systemic circulation.
4. Small amount of re-synth PLPs packed into VLDL, exported into blood capillary via exocytosis & into systemic circulation
Intracellular: lipoproteins synth in RER, PLPs synth & packed in SER, further processing in Golgi |
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Term
| Please discuss the nutritional biochemical rationales for optimizing fibre feed to cereal grain ratio in rations in order to maintain a normal lipogenesis in mature ruminants. |
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Definition
-ruminants have poor malate dehydrogenase & citrate lyase activity
-required for the citrate pathway & converting malonyl CoA into LCFAs
-cannot use gucose, propionate, AAs etc for lipogenesis
-acetate prod by fermentation of cellulose is the primary lipogenic precursor
-need to balance grain:fibre ratios so that adequate amounts of propionate (gluconeogenic) & acetate (lipogenic) are being produced |
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Term
| Discuss why mature ruminants (e.g. cows) are not susceptible to the development of obesity and artherosclerosis compared with monogastric species of pigs, poultry, rabbits, horses, and humans. |
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Definition
-other species can use all energy substrates (glucose, AAs, acetate, lactate, glycerol, ethanol) for lipogenesis
-ruminants have poor malate dehydrogenase & citrate lyase activity so cannot convert these precursers into lipogenic products
-ruminants are less susceptible to obesity & atherosclerosis (excess blood cholesterol) |
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Term
| Discuss why HDL concentration is considered a good cholesterol biomarker in blood in animals concerned with atherosclerosis and cardiovascular health. |
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Definition
-many extrahepatic tissues synthesize cholelsterol
-liver (and some SI) produce HDL which picks up excess cholesterol & transports it into liver cells through the hepatic Scavenger Receptor B1 (SR-B1)
-only the liver expresses SR-B1
-cholesterol is disposed of via the ATP-powered ABC-1 cholesterol pump for exporting cholesterol into HDL
-HDL cholesterol is good, lower risk of build up in peripheral tissues such as blood vessels |
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Term
| iscuss why LDL concentration is considered a bad cholesterol biomarker in blood animals concerned with atherosclerosis and cardiovascular health. (5 points) |
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Definition
-LDL are remaining particle after TGs are removed via VLDL by extrahepatic tissues, rich in cholesterol / CE
-LDL receptors are expressed by wide range of extra-hepatic tissues
-uptake LDL particles & obtain the cholesterol/cholesterol ester being transported
-excessive uptake of LDL particles by CV sytems increases risk of atherosclerosis |
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Term
| What are the major routes of body cholesterol disposal in animals in order to maintain a healthy blood cholesterol homeostasis? (7) |
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Definition
IN LIVER
MAJOR 99%
-cholesterol used to synthesize bile acids & salts, secreted via entero-hepatic circulation
-cholesterol secreted in liver via enterohepatic circulation
-viscous fiber is required to flush out bile acids containing cholesterol
MINOR 1%
-membrane structure & function
-stored a cholesterol ester in all tissues
-steroid hormone & Vit D synthesis |
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Term
| Discuss the nutritional biochemical bases of ketosis in high-milk yield dairy cows with poor appetite and low voluntary feed intake and its impact to their health. |
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Definition
-animals often go off-feed at peak lactation & post-parturition
-extensive LCFA catabolism in skeletal & cardiac muscle via beta oxidation to produce ATP in mitochondria
-generates ketone bodies
-exceeds the liver's capacity to handle byproducts
-inefficient means of supplying energy
-blood pH lowers due to presence of ketone bodies
-lower pH demineralizes bone
-need to ensure animals are taking in enough glucose to meet energy requirements so they don't suffer metabolic acidosis/ketosis |
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Term
| Discuss the major factors affecting intestinal Ca absorption and specifically the effect of less optimum dietary Ca to P ratio in animals. (6)? |
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Definition
-phytase must be present to release Ca2+ bound in phytate (plant sources)
-if Ca:P is suboptimal, insoluble Ca-P complexes are formed in gut which cannot be absorbed
-luminal & physiological factors affect Ca2+ uptake, expression of the apical transporter, intracellular Ca2+ binding proteins and the basolateral Ca2+-ATP pump |
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Term
| Discuss relative importance of the major routes of excretions in maintaining whole body Ca and P homeostasis in animals. (4) |
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Definition
Calcitriol: stimulates Ca resorption in renal tubule, reduces CA excretion in urine, enhances intestinal absorption
-increases Ca availability & mineralization in bones
-excreted through indigestible fecal loss, post-absorptive fecal loss of endogenous Ca, post-absorptive metabolic urinary loss
-40-60% of Ca is retained |
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Term
| Discuss how bowel or other local organ and tissue infection or inflammation influence bone mineral resorption and bone health in animals. |
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Definition
-infection results in increased levels of cytokines in the blood as an inflammatory response
-cytokines cause mobilization of bone minerals, increased bone resorption
-increases endogenous loss of Ca from the gut |
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Term
| Discuss relative importance of the major routes of excretions in maintaining whole body K, Na, Cl, Mg, and S homeostasis in animals. |
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Definition
-primarily secreted through the urine
-often fed in excess
-very little fecal/endogenous losses |
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Term
| Discuss the major routes of Fe excretions and why animals especially young animals are susceptible to Fe toxicity. (6) |
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Definition
-Fe is difficult to excrete
-minimal losses through feces, urine, sweat or blood
-excess Fe is stored as hemosiderin
-endogenous iron is recycled between tissues, can be secreted into gut lumen via bile secretion by is often reabsorbed, may be excreted in feces
-if Fe injections are too high in young animals, they are highly susceptible to toxicity
-no active excretion mechanisms available |
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Term
Please discuss relative importance of the major routes of excretions in
maintaining the whole body Cu, Mn, Zn, Se, and Cr homeostasis in animals. |
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Definition
Cr: primarily secreted & excreted in urine
Cu: bile secretion then excreted in feces
Mn: bile + pancreatic & intestinal secretions then excreted in feces
Se: urinary secretion as trimethyl selenium essential, but primary excreted in feces
Zn: excreted via feces, inorganic salt complexes with indigestible fiber as well as pancreatic & intestinal secretions
Other than Cr, the others must be pumped out via intrahepatic circulation (bile). Cannot be excreted through the urine as they are charged ions, and would need binding proteins to be able to be transported in blood |
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Term
| Discuss why and how a considerable amount of metabolic energy ATP is used for maintaining whole body homeostasis. |
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Definition
Active nutrient transport
-carries nutrients across mmbs via pumps powered by ATP (eg Na/K pump)
Secondary Active Nutrient Transport
-transport proteins directly coupled with other charged ions & [%] gradient established by ATPase or ion pumps
-costs energy to use these pumps, and if ions are present in excess then there will be a significant energy cost required to maintain homeostasis |
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Term
| Discuss how dietary (both synthetic supplemental or natural forms in feeds or foods) individual lipid-soluble vitamins are digested (if needed) and absorbed in animals. |
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Definition
-all lipid soluble vitamins are released from fat tissue via hydrolysis by lipases
-they are then packed into CM with cholesterol, transferred into lymphatic circulation bypassing the liver
-fat/oil loading in diets promotes absorption
*ADE, K1, K2 |
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Term
Please discuss how dietary (both synthetic supplemental or natural forms in
feeds or foods) individual water-soluble vitamins are digested (if needed) and
absorbed in animals. |
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Definition
-often require some hydrolysis or release from proteins in feed matrix by enzymes
Dietary individual water-soluble vitamins are digested and absorbed again through
specific transporters. They are absorbed via specific saturable transport systems across
the small intestinal gut apical membrane and is absorbed via the portal vein.
-enter blood circulation |
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Term
| vitamins in maintaining their whole body homeostasis in animals. |
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Definition
excreted via bile secretion & leaves body via feces
-often are not able to be completely catabolized (D3, E)
-some A can be excreted in urine |
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Term
Please discuss the major routes of excretions of individual water-soluble
vitamins in maintaining their whole body homeostasis in animals. |
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Definition
-some B2/B3 bile secretion in feces
-mainly urinary secretoin
-B12 , B9 via bile secretion in feces (too large a molecule for urinary secretion)
-all others are readily excreted in urine |
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Term
| Discuss the biological reasons of excreting certain lipid-soluble and water-soluble vitamins via the route of the biliary secretion (entero-hepatic circulation) in maintaining their whole body homeostasis in animals. |
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Definition
-lipid soluble are not soluble in blood, renal excretion is not possible
-B9 & B12 are large molecules so cannot pass through renal tubules
-bile duct is large enough to accommodate larger compounds |
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