Monogastric Digestion/Absorption

Mouth

1. Food acquisition

2. Mechanical breakdown - mastication

3. Saliva

- add moisture (lubrication)

- buffer (bicarb)

- taste

- Amylase (start starch digestion – pigs and primates only; very minute roll)

Esophagus - transportation

Stomach

1. esophageal, cardiac, fundic, and pyloric regions

2. Two secretions

- HCl – perietal cells (pH ~ 2.0; chemical reaction NOT enzymatic)

- pepsinogen – chief cells (¯ pH = pepsin (active enzyme) HCl)

3. Pyloric region regulates passage of feed (digesta)

Small Intestine (enzymes from SI and Pancreas)

1. CHO

- starch ® glucose

- fiber ® fiber

2. Fats

- triglycerides ® glycerol + fatty acids

3. Protein

True Protein ® amino acids, (some not digested)

NPN ® out (some absorbed, not good)

4. Minerals ® absorbed

5. Vitamins ® absorbed

Large Intestine = H₂O absorption (minor mineral and H₂O soluble vitamins)

Ruminant Digestion/Absorption

Mouth

1. Food acquisition – tongue primary importance

2. Mechanical breakdown – mastication (no front upper teeth) remastication

3. Saliva

- add moisture (lubrication)

- **buffer (bicarb)

Esophagus - transportation

Reticulirumen * No enzymes from animal (25-30 billion bacteria/mL and 200,000-500,000 protozoa/mL)

1. CHO

- starch ® energy for microbes – VFA byproduct

- cellulose ® energy for microbes – VFA byproduct

VFA absorbed through wall of rumen, primary source of energy for the animal (up to 100% of energy needs)

2. Fats

- triglycerides ® glycerol (® VFA)+ fatty acids

3. Protein

True Protein ® amino acids ® microbial protein, (some not digested and goes to SI – by-pass or undegradable protein)

NPN ® microbial protein

4. Vitamins ® B vitamins synthesized

Omasum - H₂O absorption

Abomasum – True stomach, HCl, pepsinogen – see monogastric notes

Small Intestine (enzymes from SI and Pancreas)

1. CHO – already digested and absorbed

2. Fats - fatty acids absorbed

3. Protein

Microbial and by-pass Protein ® amino acids

4. Minerals ® absorbed

5. Vitamins ® absorbed

Large Intestine = H₂O absorption (minor mineral and H₂O soluble vitamins)

Young Ruminants: Essentially monogastric – only abomasum is functional

3 weeks: Rumen begins to become fumctional

3 months: (4 mo.) fully functional

Esophageal Groove: muscle, during first 3-4 months of life active. Nursing stimulates it closing – milk by-passes rumen and goes into abomasum.

Terms

Regurgitate: to cast up "digested" feed to the mouth

Ruminate: Regurgitation, chewing, reswallowing

Eructate: Elimination of gas via belching

Gas produced by bacteria and protozoa

CO₂ and CH₄

Bloat = inability to expell gas

Swallow

Regurgitate

Chew bolus

Swallow

Another bolus regurgitated