Metabolism and Regulation of Body Temperature Physiology I Metabolism and Regulation of Body Temperature Dr Than Kyaw 23 October 2011

Nutritional Food and Energy Metabolism What are nutritional food? Types of food How they are used in the body? Body Temperature and Thermoregulation Heat production Heat exchange form and to the body Thermal control Hypothermia and hyperthermia

Nutritional feeds Food or Feed? Feed: edible things containing nutrients essential for animal’s growth and production Basic feeds Protein sources Carbohydrate and lipid sources Vitamins and mineral sources Water

Nutritional feeds Concentrates (mainly mono-gastric animals) What are they? Roughages (mainly – ruminant animals) Digestion and fate of the digested material GUT INSTESTINE BODY TISSUES Intake of feed products Absorption BLOOD Use store Digestion

Rumen microbes (micro flora) - 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.

Protozoan covered with chains of bacteria Bacteria attacking a strand of Fiber taken from a cow’s rumen. Protozoan covered with chains of bacteria

- 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 Catabolism - chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material Anabolism Constructive process e.g. Synthesis of proteins from a/a Metabolism Catabolism Destructive process e.g. Break down of protein into individual a/a Both processes take place in the body at the same time

Metabolism 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 tract 2. Post-absorptive state - the period during which there is no net absorption Many hormones contributes to the regulation of metabolism

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 Absorptive state Portein 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 Glycogen, lipid

Absorptive period Metabolic fate of glucose, amino/a, and tryglycrides absorbed form GI tract Chylomicron = tryglyceride+ cholesterol+ Intracellular protein

Used for protein synthesis by all cells Metabolism Absorptive state uptake of glucose by Blood Glucose Muscle, Liver (Stored as glycogen) Insulin uptake of amino/a Amino acids Used for protein synthesis by all cells Insulin - All essential amino/a are needed (balanced ration)

(low density lipoproteins) Metabolism Absorptive state - Protein synthesis is slow; not all amino/a used up Excess amino/a - cannot be stored as in glucose Triglyceride synthesis path way mainly in hepatocytes and secreted into the blood stream as lipoproteins (VLDLs, very low density lipoproteins) Enters Gluconeogenesis (liver, kidney) Chylomicrons – produced in Intestinal cells Lipoproteins – produced in liver Chylomicrons , Lipoproteins in blood LDLs (low density lipoproteins) Higher cholestrol Lipoprotein lipase

Metabolism Absorptive state Formation of chylomicrons in an intestinal cell

Metabolism Post-absorptive state After digestion & absorption - blood glucose level - Glucose storage - Synthesis of glycogen, protein, lipids stop Insulin ( cell) secretion Release of stored glucose Glucogenolysis Glucagon (α cell) secretion stimulate What happened after stored glucose and glycogens are used up?

Metabolism Post-absorptive state Lipolysis - Adipose tissue Fasting Maintenance Lipolysis - Adipose tissue Gluconeogenesis - proteins Growth hormone Glucocorticoids Exercise Work Rapid depletion of stored glycogen in muscle ( within 2-3 min) Other energy supplies Glycogenolysis in liver & non-working muscles Lypolysis in adipose t/s Rapid mobilization - Catecholamines - Glucagon - Insulin

Metabolism Post-absorptive state Blood glucose in Ruminants 45 – 80 mg/dL Dog 70 - 110 mg/dL Horse 60 – 110 mg/dL Blood glucose in Ruminants 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

Metabolism Post-absorptive state Blood glucose is maintained by Glucagon Continuous, high rate of gluconeogenesis (liver) VFA (propionic/a) Maintenance of blood glucose level

Simplified gluconeogenesis in ruminants Propionate (Phosphoenolpyruvate)

SIMPLIFIED GLYCOLYSIS 2 ATP lost 8 ATP from glycolysis 6 ATP from oxidation of pyruvate 24 ATP from Kreb cycle Total: 38 ATP for each molecule of glucose 4 ATP gained

Combustion of glucose molecule C6H12O6 + 6O2 −→ 6CO2 + 6H2O. 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

Summary of metabolic organs and mechanisms

Ketosis Ketone Body Formation Acetone Acetoacetate β-hydroxybutyrate High in blood, urine, and milk High milk production Starvation – Negative Energy Balance (BCS 4 or 5) Massive Fat Mobilization

Ketosis 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 Treatment – glucose infusion Glucocorticoides injections - enhance gluconeogenesis Feeding sodium propionate (unpalatable)

Simplified gluconeogenesis in ruminants Propionate (Phosphoenolpyruvate)

Body Temperature and Heat regulation