Avian & Ruminant Digestion & Applied Nutrition

avian digestive system

• crop

• proventriculus

• gizzard

• caeca

• cloaca

the crop

• secretes mucus to lubricate food

• expanded part of esophagus that stores food

proventriculus

• glandular part of the bird’s stomach where feed digestion begins

• considered the “true stomach”

  • HCL and pepsin begin digestion

gizzard

• mechanical part of stomach

• consumed feed and digestive “juice” pass into this organ for grinding, mixing, mashing

intestines and accessory organs

• function the same as any monogastric

ceca

• birds have 2

• some water in the digested material is reabsorbed here

• site of fermentation of any remaining coarse materials

cloaca

• digestive wastes mix with wastes from the urinary system

ruminant’s digestive system

• the nutrients presented to the animal after ruminal fermentation are vastly different than those entering the rumen as feed

• can utilize dead bacteria as well

1. rumen

• fermention vat

• aerobic and anaerobic microrganisms present

  • digestion → volatile fatty acids, absorbed → liver to make glucose

  • papillae lining

  • muscular pillars (mixing)

  • not functional at birth

volatile fatty acids

molecules that bacteria make as they digest cellulose

1. proprionate

2. butyrate

3. acetate

3. omasum

• “manyplies” - like folds of cloth

• no enzymes

• accepts only small particle sizes

• absorbs water

4. abomasum

• “true stomach”/ gastric stomach

• secretes enzymes

• mucus

• digestion of macromolecules

rumen microbes

• bacteria, fungi, protozoa

protozoa

• large (unicellular) organisms

• ingest bacteria and feed particles

• engulf feed particles and digest carbohydrates, proteins, fats

• # of these is affected by diet

2. reticulum

• honeycomb

• no enzymes

• contracts to help regurgitate food for rumination

rumination process

1. swallow

2. rumen/ reticulum

3. regurgitate

4. rechewing/ mastication

5. reswallowing

fungi

• number is usually low

• digest recalcitrant fiber (hard to regurgitate)

• found in a higher number if the organism eats more fibers

bacteria

• 200 species w/ many subspecies

• 1010—1012 cells/mL

• 99.5% obligate anaerobes

2 types of bacteria

cellulolytic and amylolytic

cellulolytic bacteria

fiber digesters

• produce cellulase

• ph 6-7

• byproduct of digestion is VFAs

amylolytic bacteria

starch + sugars

• ph 5-6

• byproduct of digestion is VFAs

• lactate is also a byproduct of digestion

lactic acidosis

too much grain too fast

• rapid drop in rumen pH

3 main volatile fatty acids

acetate, proprionate, butyrate

liver

proprionate becomes glucose in the

specialized finishing operations

high quality, high energy feeds

• designed to bring cattle to market weight in as little time as possible

• usually cattle fed 120-150 days

displaced abomasum

• may occur after calving

• can occur when cows are quickly transitioned to a high energy diet

  • rumen bugs dont have time to adapt, intake is lower, more opportunity for abomasum to move

• move out of place and “twist” the intestine

symptoms of displaced abomasum

• loss of appetite

• drop in milk yield

• reduced rumination

• mild diarrhea

microbe benefit to ruminant

symbiotic

• digestion of cellulose + hemicellulose

• provision of high quality protein

• production of VFA

• production of vit. B

• detoxification of toxic compounds

ruminant benefit to microbes

• housing

• garbage

• nutrients

• optimal environment for growth

endogenous enzymes

• originate in the organism

pepsin, lipase, amylase

exogenous enzymes

• originate outside of the organism

cellulase, hemicellulase

microbiome (in ruminant gut)

bacteria

carbohydrates

amylase breaks down

lipids

lipase breaks down

proteins

pepsin breaks down

HCl

____ activates protein digesting enzymes in stomach

secretin and cck

hormones from duodenum that signal to pancreas to release digestive enzymes

secretin

signals pancreas to release bicarbonate secretion

cck

signals to pancreas to release enzymes and bile

• from duodenum

cells that line the stomach

1. chief cells

2. parietal cells

chief cells

release pepsinogen

parietal cells

release HCl

pepsin

HCl breaks pepsinogen into _______

amylase

pancreatic enzyme that breaks down carbs

trypsin

pancreatic enzyme that breaks down proteins

lipase

pancreatic enzyme that breaks down lipids

maltase

brush border enzyme that breaks down carbs

peptidase

brush border enzyme that breaks down proteins

trypsinogen

inactive enzyme for protein digestion

• produced in pancreas, converted to trypsin in SI

sodium bicarbonate

_______ _____________ from duct cells buffers stomach acid

enterokinase

trypsinogen is broken down into trypsin by

cells that line duodenum

secretin and cck are produced by ______________

proprionate

VFA that is utilized in liver for glucose production

• necessary for ruminant to produce sugar