Ruminant GIT (Pelzer) Flashcards
Ruminants are ? fermenters
foregut (rumen, reticulum and omasum)
Why do ruminates ruminate (chew their cud)?
to break food down into smaller particles so that fermentation in rumen can take place on a larger surface area
How many gallons/liters can can cow’s stomach hold?
60 gallons // 240 liters
why don’t lambs, kids and calves ruminate?
Forestomach hasn’t fully developed yet. Also, they drink milk, so no need for fermentation yet.
Describe the flow of milk in ruminant stomach
Esophagus -> esophageal groove -> thru reticulo-omasal opening ->-> abomasum
What stimulates closure of the esophageal groove?
- anticipation of suckling
- act of suckling
- fluid containing salts (Ca2+ and Na+– signal receptors in pharynx)
What diminishes closure of esophageal groove?
- after weaning and age
- can be stimualted by antidiuretic hormone (ADH – production stimualted by hypothalmus – animal becomes dehydrated -> ADH rises -> seeks out water -> water bypasses rumen and into abomasum)
When do the rumen papillae begin to develop?
when animal begins to eat solid material and volatile acids are produced (VFAs)
What diet helps the development of rumen musculature?
Solid food – Grain diets
How are microbes, which are required for rumen fermentation, obtained?
They are obtained post-natally
1. environment (eating/putting random things into their mouths)
2. mother licking baby @ time of birth
3. presence of other ruminants (shared water, shared grazing or feeding areas)
5 functions of forestomachs
- Catch all of the feed and water consumed
- Provide a vat for fermentation to occur (keep process “warm” @ 97ºF)
- Form cud (so that food can be rechewed into smaller pieces
- Absoprtion of VFAs
- Control outflow
What forage do cows eat?
Pasture Forage
- Legumes (highest in protein; alfalfa)
- Grass (10-20% dry matter)
Processed Forage
- Hay (90% dry matter)
- Silage (fermented)
increase in plant maturity = decrease in digestibility
- grass more digestible if cut in spring (immature) versus in/after summer (mature)
- herbivores require concentrate to meet adequate vitamin/mineral needs (concetrate sources: grain/non-fortified or commercial/fortified)
Structural components of forage
- Complex CHOs: cellulose, hemicellulose and pectin
- Lignin: not a CHO and is not digestible; content increases as the plant matures + warmer temps
- Fiber = cellulose, hemicellulose, lignin
- Protein (legumes+++)
- Soluble CHOs (simple sugars)
incr. in plant maturity = decr. in digestibility (e.g. spring vs summer)
Contents of grain
- Soluble CHOs – rapid fermentation
- Protein (legumes/soybean meal > wheat/oat > barley > corn)
- little fiber
Grain overload -> grain is highly digestible = highly fermentable -> decreases the pH b/c of VFA production -> injected sclera, sloshy rumen, tachycardia and tachypnea
Role of microbes in ruminant stomach (4)
- Produce cellulase (breaks down complex CHOs into mono/oligosaccharides)
- Break sugar down into VFAs (acetate, propionate, butyrate)
- Break down soluble CHOs into VFAs
- Break down proteins into AAs and NH3
microbes produce enzymes that are required for fiber digestion
Microbes are comprised of what?
- Lots of bacteria (mostly anaerobic) that produce enzymes which break down fiber, soluble CHOs and proteins
- Fungi (yeast) for plant cell wall digestion
- Protozoa (anaerobic) to ingest bacteria, as well as starch and protein
3 associations of bacteria
- Fluid-associated
- Particle-associated
- Epithelium-associated
What provides 60-80% of energy requirements in ruminants?
Volatile Fatty Acids (VFAs)
- different from dogs/cats, humans, etc. who utilize on glucose
Ratio of VFAs on a high-fiber diet
70% acetate, 20% propionate, 10% butyrate
How is fat digested in ruminants?
- only partially fermented; get digested in SI like in monogastric species
- free fatty acids cannot be absorbed from rumen; get absorbed in SI
- rumen protected fat pass directly to SI to be absorbed
How is protein absorbed in ruminants?
Most is fermented: microbes break down protein into peptides, which then get absorbed:
- absorbed and turned into microbial protein
- absorbed and degraded into NH3 (ammonia), then into microbial protein
How is urea produced and where is it excreted in ruminants?
Produced by protein breakdown, excreted in the SALIVA (other species: excreted in urine) –> urea in saliva gets recycled and incorporated into microbial protein
How much saliva is produced in cows daily and why?
25-50 gallons/day
- saliva recycles water
- recycles NH3 via urea
- has HCO3- (a buffer)
- recycles electrolytes (K and P)
- helps when eating forages
What temperature must forestomach be for fermentation?
37ºC (98.6ºF)