Animal Nutrition The need to feed'

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Animal NutritionThe need to feed.
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Animals Drives Eating Behavior

• Animals can be Herbivores, Carnivores or
  Omnivores, and have adaptations to match the type
  of food they eat.
• Animals are also diverse in how they obtain their
  food. They can be suspension feeders, substrate
  feeders, fluid feeders or bulk feeders

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A Need to Maintain Homeostasis

• The regulation of glucose in the blood is an
  example of negative feedback control.

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Caloric Balance and Nourishment

• An adequate diet includes enough fuel to do
  cellular work and organic monomers for organic
  molecules (called essential nutrients)
• If an organism is chronically consuming less than
  it is expending it is undernourished.
• If an organism is chronically consuming more than
  it is expending then it is overnourished.
• An organism can be malnourished and overnourished
  at the same time.

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Excess Energy

• If excess energy is taken it is stored as
  glycogen in the muscles and as fat.

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Fat as an Adaptation

• Fat hording as an adaption The body tends to
  store excess fat molecules rather than use them.
  This is a survival mechanism for survival in
  times of need.
• Fat storage-
• Leptin is a hormone made by adipsose tissue that
  regulates fat storage and use.
• High leptin levels tell the brain to decrease
  appetite. Loss of body fat decreases leptin,
  stimulating hunger. Research has shown some
  animals have a defect in the gene that makes
  leptin.
• In most obese people, however, leptin levels are
  high, but the brian doesnt detect it. This has
  lead to the hypothesis that leptin is used in
  humans to prevent weight loss rather than weight
  gain.

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Essential Nutrient
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The Journey of Food as it Travels from Mouth to
Anus

• 1. Food enters oral cavity where mechanical
  breakdown occurs (chewing). Salivary glands
  excrete saliva that has amylase and carbohydrate
  digestion begins. Mucin (a slippery
  glycoprotein) is also excreted which protects
  the lining of the mouth and lubricates the food.
  Food saliva a bolus which is pushed to the
  back of the throat and into the esophagus. When
  swallowing, the epiglottis covers the glottis
  preventing food from entering the trachea. The
  top of the esophagus is voluntary and the rest
  involuntary, moving food by peristalsis.

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Digesting Cont

• 2. The bolus enters the stomach through the
  cardiac sphincter. Gastric juices with HCl and
  Pepsin are excreted. ( pepsinogen (inactive) ?
  pepsin (active) in the presence of HCl). Acid
  breaks down the extracellular matrix of food, and
  pepsin breads down protein. Mucus is secreted by
  the stomach to protect the lining of the stomach.
  Bolus is now acid chime, and exits the stomach
  via the pyloric sphincter.

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Digestion Cont

• Acid Chyme enters the small intestine at the
  duodenum.
• Chyme is mixed with enzymes and bicarbonate from
  the pancreas.
• Pancreatic trypsin and chymotrypsin for
  protein digestion
• Pancreatic nucleases for nucleotides
• Pancreatic lipase for fat.
• Bile made in the liver and stored in the gall
  bladder is added to the small intestine to
  emulsify fat.
• Most digestion is completed in the duodenum.

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Digestion Cont

• In the Jejunum and ileum portion of the small
  intestine nutrients are absorbed. The villi and
  micro villi increase the surface area for
  absorption.
• Anatomy of Villi and absorption
• The villi have capillaries and a lacteal.
• Sugars can pass directly into the capillaries
  that empties into the hepatic portal vein that
  leads to the liver.
• Glycerol and Fatty acids are absorbed by
  epithelial cells and recombined into fats. These
  fats are mixed with cholesterol and proteins to
  make chylomicrons which enter the lacteals via
  exocytosis. The lacteals empty into the
  lymphatic system.
• See p. 859 for a good summary of digestion.

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Digestion Cont

• 6. All material left over enters the large
  intestine where water is reabsorbed. Bacteria
  digests cellulose and releases Vitamin K, biotin,
  folic acid and Vitamin B.
• 7. Anything left over exits through the rectum.
  Two sphincters control this process voluntary
  and involuntary. Contractions of the large
  intestine open the involuntary sphincter putting
  pressure on the voluntary one.

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Special Adaptations for Different Diets

• Teeth Cutting , grinding, hollow fangs ect all
  adapted to a particular organism feeding habits
  in its niche.
• Digestive tract adaptations
• Herbivores tend to have longer digestive tracts
  to digest vegetation. Ex. The cecum of a rabbit
  is much larger proportionally than ours.
• Many herbivores work symbiotically with microbes
  to break down the cellulose of cell walls. EX.
  Ruminates.
• Carnivores tend to have larger stomachs because
  the often go for a long time between meals.