Nonruminant Herbivore Digestion/Absorption

Mouth (see monogastric)

1. Food acquisition

2. Mechanical breakdown - mastication

3. Saliva

Esophagus - transportation

Stomach (see monogastric)

Small Intestine (enzymes from SI and Pancreas) – See Monogastric

Large Intestine

Cecum ~same as rumen, a pocket off of the LI

CP – already digested and Absorbed

Starch - already digested and Absorbed

Cellulose – VFA produced and some absorbed

B vitamins synthesized, but not absorbed in cecum

L.I. = H₂O absorption (minor mineral and H₂O soluble vitamins)

Pre-gastric VS. Post-gastric digestion of cellulose

Poultry Digestion/Absorption

Mouth (beak)

1. Food acquisition – no teeth

2. Poorly developed salivary gland

Esophagus - transportation

Crop – part of esophagus – ingesta holding and moistening, some species have a little fermentation

Proventriculus – ingesta passes through quickly

Gastric juice produced - HCl & pepsinogen

Ventriculus = Gizzard – very muscular to contract for physical ¯ particle size

Contains stones (grit) to assist in this physical breakdown

No enzymes, but HCl and pepsin from Proventriculus

Small Intestine – see monogastric

Enzymes ?? Lactase??

Ceca – 2 "cecums" – same as in horse, but not as extensively used

Large Intestine – see monogastric

Feces and urine (uric acid) are both excreted through same opening (vent)

The Pancreas

Two types of tissue

Acini = secrete the various digestive enzymes

Islets of Langerhans = secrete hormones – two types of islet cells

a = secrete glucagon

b = secrete insulin

glucagon and insulin are antagonistic, play key roles in blood glucose concentration

The Liver

Gland: largest and probably the most important gland in the body

Functions:

Bile synthesis = emulsifies fat – allows for digestion and absorption

Glucose regulation (blood)

Glycogen – storage and release (animal starch)

Gluconeogenesis – synthesis of glucose

Deamination of AA = remove amino group from aa, be used for energy – N goes to Urea cycle

Fatty Acid synthesis – from CHO and protein

Formation of ketones

Formation of lipoproteins, phospholipids, & cholesterol

Storage = Vit. A, ~D, B12 , Fe

Detoxification = first place nutrients from SI go to via blood, toxins detoxified (hopefully)

Formation of plasma proteins = fibrinogen, prothrombin, (blood clot formation)

Degradation and Excretion of Hormones = steroid hormones, cholesterol

Bile

Produced = continuously by the liver

Stored = gall bladder

Secreted = into SI as ingesta enters from the stomach (cholecystokinin)

Functions

Fat Emulsification = detergent action (break down particles (globules)

Fat Absorption = fat and fat soluble vitamin absorption

**Increase fat solubility in water

Digestive Enzymes

Enzymes: catalysts for normal spontaneous reactions (slow rate). Catalysts are not permanently affected by the reaction. Enzymes act as organic catalysts. All physiological function intimately linked to enzymes. (digestion, kidney excretion, muscle contraction, tissue growth/breakdown ® turnover, cellular respiration)

Nature & Characteristics:

Protein: All enzymes are proteins

Produced: by living cells

Heat Labile: destroyed by heat

Specificity:

a. 1 bond 1 molecule - maltase

b. >1 bond 1 molecule - lipase

c. cross boundaries?? - No crossing of boundaries, ie. Lipase will not work on CHO or CP

pH: - most have optimum pH: slower (less active) at ¯ or pH

example: pancreatic amylase optimum pH is ~7.0 (neutral). If stomach contents not neutralized, amylase activity would be slow therefore incomplete starch digestion.

Temperature: - like pH, optimum temperature. Temperature is usually constant in warm-blooded animals (98.6 to 102 ^oC)

Activity:

Secreted form: (proenzyme or zymogen) have to be activated from the form they are secreted as. Pepsinogen in the presence of HCl converted to pepsin

Co-"?": some need help from "other" factors to be active

Cofactor = if enzyme requires a mineral, then the mineral is a cofactor

Coenzyme = if an enzyme requires a vitamin, the vitamin is a coenzyme

Mechanism of Action:

Substrate: compound to be acted on by the enzyme

Active Site: lactation on the enzyme where it attaches to the substrate

Product: the released result of the reaction

Maltose acted on by maltase to form 2 glucose

Amylose acted on by amylase to form X glucose

Protein acted on by pepsin to form oligopeptides

Fact acted on by lipase to form fatty acids