• Chapter 41

Animal Nutrition

Nutritional requirements• Undernourishment: caloric

deficiency• Overnourishment (obesity):

excessive food intake• Malnourishment: essential

nutrient deficiency• Essential nutrients: materials

that must be obtained in preassembled form

• Essential amino acids: the 8-10 amino acids that must be obtained in the diet (Arginine, Histidine – Infants)

• Essential fatty acids: unsaturated fatty acids

• Vitamins: organic coenzymes

• Minerals: inorganic cofactors

Food types/feeding mechanisms• Opportunistic

• Herbivore: eat autotrophs

• Carnivore: eat other animals

• Omnivore: both

• Feeding Adaptations

• Suspension-feeders: sift food from water (baleen whale)

• Substrate-feeders: live in or on their food (leaf miner)

(earthworm: deposit-feeder)

• Fluid-feeders: suck fluids from a host (mosquito)

• Bulk-feeders: eat large pieces of food (most animals)

Overview of food processing• 1-Ingestion: act of eating• 2-Digestion: process of food break down • enzymatic hydrolysis • intracellular: breakdown within cells (sponges)• extracellular: breakdown outside cells (most animals)• alimentary canals (digestive tract) • 3- Absorption: cells take up small molecules• 4- Elimination: removal of undigested material

Mammalian digestion• Peristalsis: rhythmic waves of contraction by smooth muscle• Sphincters: ring-like valves that regulate passage of material• Accessory glands: salivary glands; pancreas; liver; gall bladder

Mammalian digestion

• Oral cavity•salivary amylase •bolus

• Pharynx•epiglottis

• Esophagus• Stomach

•gastric juice•pepsin/pepsinogen

(HCl) •acid chyme•pyloric

sphincter

Figure 41.3 Homeostatic regulation of cellular fuel

STIMULUS:Blood glucose

level risesafter eating.

Homeostasis:90 mg glucose/100 mL blood

STIMULUS:Blood glucose

level dropsbelow set point.

When blood glucose level rises, a gland called the pancreas secretes insulin,a hormone, into the blood.

1

Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops.

2

When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin.

3

Glucagon promotes the breakdown

of glycogen in the liver and

there lease of Glucose into the blood,increasing

blood glucose level.

4

Figure 41.19 The duodenum

Liver Bile

Acid chyme

Stomach

Pancreatic juice

Pancreas

Intestinaljuice

Duodenum of small intestine

Gall-bladder

Mammalian digestion

• Hormonal Action:• Gastrin food---> stomach

wall ---> gastric juice• Enterogastrones

(duodenum)• 1-Secretin

acidic chyme---> pancreas to release bicarbonate

• 2-Cholecystokinin (CCK) amino/fatty acids---

> pancreas to release enzymes and gall bladder to release bile

• Large intestine (colon)• Cecum• Appendix• Feces• Rectum/anus

Figure 41.22 Hormonal control of digestion

Amino acids or fatty acids in the duodenum trigger the release of

cholecystokinin (CCK), which stimulates the release of digestive

enzymes from the pancreas and bile from the gallbladder.

Liver

Gall-bladder

CCK

Entero-gastrone

Gastrin

Stomach

Pancreas

Secretin

CCK

Duodenum

Key

Stimulation

Inhibition

Enterogastrone secreted by the duodenum inhibits peristalsis and acid secretion by the stomach, thereby slowing digestion when acid chyme rich in fats enters the duodenum.

Secreted by the duodenum, secretin stimulates the pancreas to release sodium bicarbonate, which neutralizes acid chyme from the stomach.

Gastrin from the stomach recirculates via the bloodstream back to the stomach, where it stimulates the production of gastric juices.

Mammalian digestion• Small intestine •duodenum •bile• Intestinal digestion: a-carbohydrate b-protein c- nucleic acid

d-fat

Mammalian digestion• Villi / microvilli• Lacteal (lymphatic)• Chylomicrons (fats mixed with cholesterol)• Hepatic portal vessel

Evolutionary adaptations• Dentition: an animal’s assortment of teeth• Digestive system length• Symbiosis• Ruminants