Animal Nutrition

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Chapter 41

• Animal Nutrition

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Nutritional Requirements

• Adequate diet supplies three things
• Fuel for all cellular work
• Carbon skeletons raw materials for biosynthesis
• Essential nutrients substances the animal cants
  make themselves

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Glucose regulation

• Glucose major form of fuel molecule for cells
• Excess glucose is stored as glycogen in the liver
  and muscles of an animal

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Caloric Imbalance

• Undernourishment taking in fewer calories than
  the body needs
• Breakdown of proteins for energy
• Brain becomes protein deficient
• Muscle breakdown
• Overnourishment taking in more calories than
  the body needs
• Storing excess food as fat

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Obesity

• Human body can store fat for energy
• There is a genetic limit on how much
• Due to a hormone called leptin
• High levels of leptin depresses appetite

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Essential nutrients

• Supply the raw materials for biosynthesis
• Malnourishment (different than
  undernourishment) organism that is missing an
  essential nutrient in the diet
• Herbivores and osteophagia
• Essential Amino acids
• There are 20 amino acids (these are carbon
  skeletons for proteins)
• We can synthesize about half of these
• Sources of amino acids are meats, eggs, cheese,
  and other animal products

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Essential nutrients cont.

• Essential fatty acids most fatty acids can be
  made by the body
• Linoleic acid must be present in the diet
• Vitamins organic molecules required in the diet
  in small quantities

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Essential nutrients

• Minerals simple inorganic nutrients, required
  in small amounts
• Calcium and phosphorous for bone
• Calcium for muscles

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Food Types and Feeding Mechanisms

• All animal eat other organisms
• Herbivores eat mainly autotrophs
• Carnivores eat mainly heterotrophs
• Omnivores eat both plants and animals
• Most animals are opportunisitc eating what is
  available

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Feeding Mechanisms

• Suspension feeders sift small food particles
  from the water.
• Substrate feeders live in or on their food
  source
• Maggots, leaf miners

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Feeding Mechanisms

• Fluid feeders make a living by sucking nutrient
  rich fluids from a living host
• Mosquitoes
• Bulk feeders eat relatively large pieces of food

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Food Processing

• Ingestion act of eating
• Digestion breaking food down into molecules
  small enough to absorb
• Absorption absorbing the monomers of molecules
  broken down during digestion
• Elimination undigested materials passes out of
  the digestive compartment

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Digestion

• How do animals digest food without digesting
  their own cells
• Food is made of the same stuff your stomach is
  made of
• Specialized compartments allow for food to be
  digested without digesting yourself
• Intracellular Digestion food vacuoles

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Digestion

• Extracellular digestion breakdown of food
  outside cells
• Enables animals to eat larger pieces of food
• Gastrovascular cavities
• End to end digestion complete digestive tracts

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Mammalian Digestive System

• Consists of alimentary canal (end to end
  digestion)
• Peristalsis - smooth muscle wave contractions to
  push the food through
• Sphincters close off tube like drawstrings
  between chambers
• Accessory glands
• Salivary glands
• Pancreas
• Liver
• Gall bladder

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Oral Cavity

• Physical and chemical digestion begins here
• Presence of food stimulates salivary glands to
  secrete saliva
• Mucin protects the lining of the mouth and
  lubricates the food
• Antibacterial agents
• Salivary amylase hydrolyzes starch
• Pharynx throat, opens to both esophagus and the
  lungs
• Esophagus conducts food from the pharynx to the
  stomach

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Stomach

• Elastic organ that stores food and digests food
• Can hold about 2 L of food and fluid
• Secretes gastric juice
• pH of 2 (acidic enough to dissolve iron nails)
• Breaks apart molecules held together in food
• Secretes pepsin
• Breaks down proteins
• Secreted in an inactive from called pepsinogen
  from chief cells
• Parietel cells secrete hydrochloric acid, which
  then activates the pepsinogen
• Lined with mucus, lining is replaced every 3 days
• Closed off at both ends during digestion
• Pyloric sphincter allows little bits of the food
  at a time to enter the small intestine (takes
  about 2 or 6 hours after each meal to empty the
  stomach)

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Small Intestine

• Major organ of digestion and absorption
• 6 m long in a human
• The acidic chyme from the stomach mixes with
  digestive juices from the pancreas, liver and
  gallbladder
• Pancreas neutralizes the acid so your small
  intestine will not be digested
• Liver produces bile aid in digestion of fats

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Small Intestine

• Absorption of nutrients

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Large Intestine

• Joins the small intestine at a t-shaped junction
• One arm of the T is a pouch called the cecum
• Humans have a small cecum compared to most
  mammals
• Major function is to recover water secreted by
  the small intestine
• E. coli inhabits the large intestine producing
  vitamins