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Metabolism and Regulation of Body Temperature
Dr Than Kyaw
23 October 2011
Physiology I
• Nutritional Food and Energy MetabolismWhat are nutritional food?Types of foodHow they are used in the body?
• Body Temperature and ThermoregulationHeat productionHeat exchange form and to the bodyThermal controlHypothermia and hyperthermia
Nutritional feeds
• Food or Feed?• Feed: edible things containing nutrients
essential for animal’s growth and production• Basic feeds
Protein sourcesCarbohydrate and lipid sourcesVitamins and mineral sourcesWater
• Concentrates (mainly mono-gastric animals)What are they?
• Roughages (mainly – ruminant animals) What are they?• Digestion and fate of the digested material
Nutritional feeds
Intake of feed Digestion
productsAbsorption
Use store
GUT INSTESTINE BODY TISSUES
BLOOD
- Bacteria: digestion of sugars, starch, fiber, and protein for the cow.
- Protozoa: swallow and digest bacteria, starch granules, and some fiber.
- Fungi: a small fraction of the rumen microflora
but important in splitting plant fibers open to
make them more easily digested by the bacteria.
Rumen microbes (micro flora)
Protozoan covered with chains of bacteria
Bacteria attacking a strand of Fiber taken from a cow’s rumen.
- Bacteria – account for about 80% of rumen metabolism - 1011 bacteria/ml of rumen fluid
- Protozoa – 20% (106 protozoa/ml of rumen content)
- Fungus - very small number
Metabolism
Metabolism
AnabolismConstructive processe.g. Synthesis of proteins from a/a
CatabolismDestructive processe.g. Break down of protein into individual a/a
Both processes take place in the body at the same time
- chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material
Basal metabolism (BM)
- minimum amount of energy required to maintain vital
functions in an animal at complete rest
- BM - measured in a fasting individual who is awake and
resting in a comfortably warm environment
- Many hormones contributes to the regulation of metabolism
Metabolism
- Two periods of metabolism 1. Absorptive state - the period shortly following a meal during which
nutrients are being absorbed from GI tract2. Post-absorptive state
- the period during which there is no net absorption
Metabolism
Many hormones contributes to the regulation of metabolism
- During absorptive state blood level of glucose, amino/a, triglycrides
increase (product of starch, glycogen, protein and cellulose)
- Overall goals of metabolic processes during this period is to
increase the use of these nutrients by cells of the body OR store
them for later use
Metabolism
Glucose
- predominant product of C/H digestion following a typical meal
- blood glucose level – about 150% of fasting level
- Insulin (produced by pancreas) – primary stimulant
endocrine regulator
- It affects – C/H, Protein (amino/a), lipid metabolism
MetabolismAbsorptive state
Portein
Glycogen, lipid
Chylomicron = tryglyceride+ cholesterol+ Intracellular protein
Absorptive periodMetabolic fate of glucose, amino/a, and tryglycrides absorbed form GI tract
Blood Glucose
MetabolismAbsorptive state
uptake of glucose by Muscle, Liver
(Stored as glycogen)Insulin
Amino acids
uptake of amino/a Used for protein
synthesis by all cellsInsulin
- All essential amino/a are needed (balanced ration)
- Protein synthesis is slow; not all amino/a used up
- Excess amino/a - cannot be stored as in glucose
MetabolismAbsorptive state
Enters
Triglyceride synthesis path way mainly in hepatocytes and secreted into the blood stream as lipoproteins (VLDLs, very low density lipoproteins)
Gluconeogenesis (liver, kidney)
Chylomicrons – produced in Intestinal cellsLipoproteins – produced in liver
Chylomicrons ,Lipoproteins in blood
LDLs (low density lipoproteins)
Higher cholestrol
Lipoprotein lipase
MetabolismAbsorptive state
Formation of chylomicrons in an intestinal cell
MetabolismPost-absorptive state
After digestion & absorption - blood glucose level
Insulin ( cell) secretion
Glucagon (α cell) secretion
- Glucose storage- Synthesis of glycogen, protein, lipids
stop
- Release of stored glucose- Glucogenolysis
stimulate
What happened after stored glucose and glycogens are used up?
MetabolismPost-absorptive state
FastingMaintenance
Lipolysis - Adipose tissueGluconeogenesis - proteins
Growth hormoneGlucocorticoids
ExerciseWork
Rapid depletion of stored glycogen in muscle ( within 2-3 min)
Other energy supplies1. Glycogenolysis in liver &
non-working muscles2. Lypolysis in adipose t/s
- Catecholamines- Glucagon - Insulin
Rapid mobilization
MetabolismPost-absorptive state
Ruminants 45 – 80 mg/dL
Dog 70 - 110 mg/dL
Horse 60 – 110 mg/dL
-lower than other animals (Why?)
-Relatively small amount of glucose-yielding C/H digestion in S/I-Most C/H consumed – fermentative digestion in rumen – products – VFAs (not glucose)
- acetic, propionic, butyric/a
Blood glucose in Ruminants
Maintenance of blood glucose level
Continuous, high rate of gluconeogenesis (liver)VFA (propionic/a)
Glucagon
Blood glucose is maintained by
MetabolismPost-absorptive state
PropionateCO2
(Phosphoenolpyruvate)
Simplified gluconeogenesis in ruminants
2 ATP lost
4 ATP gained
SIMPLIFIED GLYCOLYSIS
8 ATP from glycolysis 6 ATP from oxidation of pyruvate24 ATP from Kreb cycle
Total: 38 ATP for each molecule of glucose
• One mole of glucose, this reaction releases 2.80 MJ of energy • That translates to 15.6 kJ, or 3.75 kcal, per gram.
• generally rounded to 4 kcal/g of sugar
• On a per-gram basis, all carbohydrates yield essentially the same amount of energy as glucose
C6H12O6 + 6O2 −→ 6CO2 + 6H2O.
Combustion of glucose molecule
Summary of metabolic organs and mechanisms
Ketosis
Ketone Body FormationAcetoneAcetoacetateβ-hydroxybutyrate
High in blood, urine, and milk
• High milk production• Starvation – Negative Energy Balance (BCS 4 or 5)• Massive Fat Mobilization
• More common in dairy cows (peak milk production)• Rapid need of glucose for milk sugar synthesis• Increased mobilization of fat depot leads to ketone body
production
Ketosis
• Treatment – glucose infusion• Glucocorticoides injections
- enhance gluconeogenesis• Feeding sodium propionate (unpalatable)
PropionateCO2
(Phosphoenolpyruvate)
Simplified gluconeogenesis in ruminants
Body Temperature and Heat regulation