Lecture 5- The hind gut or large intestine and maintenance energy Flashcards
What is the general description of the large intestine?
large intestine= colon, cecum, appendix and rectum -cecum= pouch below the junction of the small and large intestines (at the ileocecal vave) -appendix lymphoid tissue= houses good bacteria? -colon= most of the large intestine -not coiled (unlike the small intestine) -3 sections- ascending, transverse and descneding -terminal portion is S shaped then straignthens to form recturm -one line missing
What are the 2 types of post gastric fermentations?
- Caecal fermenters • Mainly rodents, rabbits and other small herbivores • Often associated with coprophagy and caecotrophy (eat their shit again= caecotroph -coprophagy= eating shit of other species) 2. Colonic fermenters • Includes true herbivores (e.g., horse), omnivores (e.g., pig and human), and carnivores (e.g., cat and dog) • Horse has some expanded caecal fermentation in addition to greatly expanded colonic fermentation • Degree of colonic sacculation is related to importance of fibre digestion and fermentative capacity
What are some examples of caecal digesters?
-capybara: grazer -rabbit: selective herbivore -rat, mouse: omnivores
What are some examples of colonic digesters?
-sacculated: -Elephant, horse, zebra: grazers -New World monkeys: folivores -Pig, human: omnivores -unsacculated: -panda: herbivore -dog, cat: carnivore
What are the functions of the large intestine (3)?
• Re-absorption of water and compact indigestible matter into faeces • Site of absorption of vitamins produced by bacteria (e.g. fermentation) • Storage of faecal matter prior to defecation -main function is the storage of fecal matter but also absorption of water, condense the waste material
What does the large intestine look like?
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What is the histology of the large intestine?
• Absence of villi – unlike the small intestine (no enzymatic function only to protect the wall of the large intestine) • Presence of goblet cells for mucus secretion • Deep intestinal glands present in the wall
What is the physiology of the large intestine?
• Re-absorption in the large intestine includes:
- Water • Vitamins – K, biotin, and B5
- Organic wastes – urobilinogens and sterobilinogens
- Bile salts
- Toxins
• Mass movements of material through colon and rectum
• Defaecation reflex triggered by distention of rectal walls
-organic waste= from blood etc. -mass movements of material through colon and rectum=eating a meal triggers defecation quite often (viz PIC- stretch reflexes!)
What is maintenance energy?
the energy you need to keep yourself alive
- just to keep going
- need to memorise this diagram
- what you cannot digest, and also need e to get rid of fecal matter
- then energy that you can digest and then the energy that
- maintenance costs energy
What is a respiration calorimeter?
• Measures heat produced by an animal • Lavoisier and Laplace developed the first animal calorimeter in 1780 • Guinea pig in a chamber surrounded by ice -the can not if one animal is more efficient in digestion -the 1st is for guineapig
What does direct and indirect calorimetry do?
• Direct calorimetry actually measures the amount of heat given off • Indirect calorimetry measures oxygen consumption and carbon dioxide production and estimates heat given off mathematically
What is a Douglas bag?
-bag you put on a human and measure the respiration -can limit activity of the subject and the duration of measurement (extremely uncomfortable to wear)
What is the PowerLab?
-modified Douglas bag, used for sheep -The modified PowerLabTM exercise physiology system allows the measurement of acute, real time gas exchange in sheep.
What is maintenance?
- The amount of energy (or protein) needed to maintain an animal in zero energy (or protein) balance
- Strictly speaking, maintenance requirement is only measurable in a mature, non-pregnant, non-lactating animal
- But in practice the concept is widely applied to productive animals
What is efficiency?
• Maintenance feed requirements have a major effect on efficiency of feed utilisation • For instance >40% energy intake is used to support maintenance
What are the components of maintenance?
-basal metabolism, muscular work and temperature metabolism
What is basal metabolism?
- Metabolic rate in post absorptive state, with minimal activity, thermal and behavioural stress
- Affected by:
- Body size
- Species
- Age
- Previous level of nutrition
- Climate
What is the relationship between body size and heat?
- The bigger an animal, the more heat it produces
- Relationship is curvilinear
- Plotted on logarithmic scale = relationship becomes linear
What is this: log H = 1.84 + 0.75 log W?
• H = 69 W0.75 • H is heat production (kcal/d) • W is body weight (kg) • W0.75 is termed metabolic body weight -• Considerable species variation around the mean; 69 W0.75 • Sheep 75 -calculation to get the basal metabolic rate
What is dimensional analysis?
-the relationship between BMR and body mass -The relationship between surface area (A) and length (L) is: A α L2 -The relationship between mass (m), density (ρ) and volume (V) is: m = ρV -The relationship between length (L) and volume (V) is: V α L3 -The relationship between mass (m) and length (L) is: m α L3 -Length is therefore proportional to the cube root of the mass L α m0.33 -If the area is proportional to the square of the length then A α m0.67 -An animal gives up its heat to the environment in proportion to the surface area (m x constant k) – therefore ΔE/Δt = k. m0.67 -Heat generation is proportional to the metabolic rate – therefore BMR = k. m0.67 -•Actually the relationship is not quite as first noted by the theory, Kleiber observed that the relationship between mass and metabolic rate was: -BMR = k. m0.75 -The relationship holds true over 27 magnitudes of mass – from the simplest enzyme system to the metabolic performance of a whale!!
What is the relationship of basal heat production and age?
• Basal heat production, corrected for metabolic body weight, declines quickly from birth to weaning, then more slowly to maturity -metabolic rate goes down as you age -cannot eat as much
What is the relationship of basal heat production and climate?
• Prolonged cold causes increased basal heat production • Prolonged heat caused decreased basal heat production
How does muscular work affect the maintenance?
- Effects of exercise on maintenance requirements depend on
- Work intensity
- Work duration
- NRC tables usually add a correction factor of 10% of fasting heat production to account for effects of activity
- Would be higher in grazing animals
How does temperature regulation affect maintenance?
• When environmental temperature falls below the animal’s lower critical temperature, heat production must increase if normal body temperature is to be maintained
- thermoneutral zone
- between lower and upper critical zones
- above or below= will need more energy to maintain energy
What is lower critical temperature affected by?
• Lower critical temperature is affected by • Level of feed intake • Body size • Tissue insulation (condition) • Coat insulation -smaller people= colder quicker -tissue insulation= fat = if little= get colder faster
What affects the rate at which heat production increases with environmental temperature decreasing?
• Rate at which heat production increases with decreasing environmental temperature below critical is independent of feed intake
What is the effect of energy intake on energy balance?
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