Day 6 Ruminant Digestion and Fermentation

What is the true stomach?

abomasum

What are the components of the forestomach?

rumen, reticulum, omasum

Where does fermentation occur?

rumen

Where do heavy items settle in the forestomach?

reticulum

Where does absorption occur in the forestomach?

omasum

What organisms make up the microbiome in a ruminant?

bacteria, protozoa, archaea, fungi

What 3 basic plant structures are fermented?

cellulose, hemicellulose, pectin

What are the basic nutrients needed for life?

oxygen, water, energy, protein, fats, vitamins, minerals

Which 2 nutrient groups most impact a cows daily performance?

energy (starch/carbs), protein

Are ruminants fed meals?

free fed

Is the ruminant diet often changed?

no

What are the basic feedstuffs for michigan dairy cows?

fermented feeds and dry feeds

What composes the fermented feeds?

corn silage, haylage

What composes the dry feeds?

ground corn, soy bean meal, by-products

How is the feed presented?

TMR or PMR (total mixed or partial mixed ration)

What key ingredient does corn silage, corn, grasses, and some by-products add?

starch

What key ingredient does alfalfa, bean meals, and some by-products provide?

protein

Who determines how much of each ingredient is included in TMR?

nutritionists

What are starches fermented into?

volatile fatty acids

What are the "big 3" VFAs?

acetate, propionate, butyrate

What VFAs enter into krebs cycle as acetyl-CoA?

acetate and butyrate

What VFA enters the liver for conversion to glucose?

propionate

What is taken up by microbes for cell wall formation?

protein

Microbes pass to true stomach and intestines digested and provide _______% of animals protein needs

80

What are some examples of ruminant digestive upsets?

bloat, indigestion, diarrhea, acidosis, displacement

Primary causes of digestive upset are due to what?

diet

What is the primary causes for displacement?

inadequate fiber, no rumen mat, too much starch

What are the secondary causes for displacement?

metritis, mastitis, lameness, pneumonia

How can acidosis from grain overload occur?

cow sorting TMR, jail break

Clinical signs of acidosis in cattle?

depressed, dehydrated, bloat, cool ears, no ruminations, diarrhea

Ruminant saliva is alkaline and contains what?

bicarbonate and phosphate

What types of contractions does the reticulorumen undergo?

primary/mixing, rumination, eructation

What contraction type ensures adequate movement of contents back and forth between the reticulum and the rumen?

mixing

What provides the force necessary to move the liquid contents from the reticulorumen into the omasum?

mixing contractions

Chewing the cud is also known as

rumination

Rumination involves four steps. summarize them.

regurgitation, cardiac sphincter relaxes while rumen contracts moving bolus toward mouth, then re-insalivation, re-mastication, and re-swallowing occur

In rumination, the bolus is moved back towards the oral cavity by what type of contraction?

antiperistaltic wave of esophageal smooth muscle

What occurs during re-insalivation and re-mastication?

saliva added and bolus chewed

The number of chews during re-mastication is based on what?

diet

Which animal will ruminate longer, one that eats fiber-rich forage or low-fiber?

fiber rich diet

Animals consuming mostly hay ruminate approximately ____ hours.

8

What type of contraction is responsible for release of gases produced during fermentation, such as carbon dioxide and methane?

eructation

Eructation is known as ______________ contractions.

secondary

Methane-producing bacteria uses what to produce methane?

carbon dioxide produced as the microorganisms breakdown carbs and amino acids

What can happens if gasses are not released during eructation?

bloat

What can happen if bloat is not treated?

tissue hypoxia, death

The amount of gas produced by fermentation in a single dairy cow can be as much as __________ in a 24hr period.

4000L

Where does eructation begin?

secondary contractions in the caudal blind sac

The gas expelled during eructation occurs how?

during expiration

What plays a more important role in in regulating motility, enteric nervous system or central nervous?

CNS via vagus nerve

what creates the low-oxygen environment of the rumen?

small amounts of ingested oxygen are consumed by microorganisms

What allows for facultative anaerobic and protozoa to thrive in the rumen?

low-oxygen environment

When a ruminant is born, the GI tract is sterile. True/False

True

What breaks down starch and soluble carbohydrates into VFAs?

amylolytic bacteria

What breaks down components of cell walls including cellulose and pectin into VFAs?

cellulolytic bacteria

The protozoa in the rumen are usually of what tpe?

unicellular, anaerobic, ciliates

Can the ruminant live without protozoa in the GI tract?

yes

What role are protozoa thought to play in the ruminant GI tract?

slowing digestion of starches and proteins

Cellulolytic bacteria break down carbs by what process?

hydrolysis

Cellulolytic bacteria break down carbs, releasing what?

monosaccharides such as glucose and simple polysaccharides

Are the saccharides produced by starch or cellulose breakdown immediately available for use by the ruminant?

no, they are absorbed by microorganisms and metabolized to pyruvate via NAD reduction and production of 2 ATP, then converted to VFAs

Most of the VFAs are absorbed from where?

reticulorumen

What is released by rumen bacteria that breaks down proteins to form small peptide chains?

peptidases

What happens to the broken down small peptide chains in the rumen?

hydrolyzed by microorganisms to amino acids

What happens if the amino acids yielded by protein breakdown are not used to make microbial proteins?

further broken down by microbes and deaminate them into ammonium to produce VFAs

What are the two ways ammonium can be produced by microbes?

deamination of amino acids, NPN compounds (urea, nitrates)

Proteins synthesized by microbes are transported to the small intestine where they are broken down by what?

proteolytic enzymes

What are bypass proteins?

proteins that pass unaltered through the forestomach

The end products of protein breakdown are amino acids and are absorbed across intestinal mucosa into the bloodstream and taken where?

liver for protein metabolsim

What is unique about urea in the ruminant?

urea travels back to rumen and saliva to be used by microbes