Ruminant Digestive Anatomy and Function

Ruminant digestive system

• uniquely qualifies ruminant animals such as cattle to efficiently use high roughage feedstuffs, including forages

• Mouth

• Tongue

• Salivary glands

• Esophagus

• Four-compartment stomach (rumen, reticulum, omasum, abomasum)

• Pancreas

• Gallbladder

• Small intestine (Duodenum, Jejunum, ileum)

• Large intestine (Cecum, Colon, Rectum)

Anatomy of the Ruminant Digestive System

Oral cavity

Uses this to harvest forages during grazing or to consume harvested feedstuffs

tongues

• Cattle harvest forages during grazing by wrapping their _ around the plants and then pulling to tear the forage for consumption.

25000 to more than 40000

• On average, cattle take from _( prehensile bites to harvest forage while grazing each day.

• Grazing

• Ruminating

• Idling

They typically spend more than one third of their time _ , one third of their time _ , and slightly less than one third of their time _, that is neither of the two aforementioned

• roof

• lower jaw

The of the ruminant mouth is a hard/soft palate without incisors. The _ incisors work against this hard dental pad.

narrower and chisel-shaped

Incisors of concentrate selectors

wide with a shovel-shaped crown

Incisors of grass/roughage selectors are?

• Premolars

• Molars

_ and _ match between upper and lower jaws. These teeth crush and grind plant material during initial chewing and rumination.

Saliva

aids in chewing and swallowing

fats

What does salivary lipase breakdown?

• Salivary lipase

• Salivary amylase

Saliva enzymes in ruminants include

Starch

What does salivary amylase breakdown?

Saliva

is involved in nitrogen recycling to the rumen.

• buffer pH levels in the reticulum and rumen

Saliva’s most important function is to ?

50 quarts

A mature cow produces up to _ saliva per day

• sodium

• potassium

• phosphate

• bicarbonate

• urea

Forage and feed mixes with saliva containing what when consumed, to form a bolus.

Bolus

moves from the mouth to the reticulum through a tube-like passage called the esophagus.

Rumination

Also known as chewing the cud

chewing

Ruminants eat rapidly, swallowing much of their feedstuffs without _ it sufficiently (< 1.5 inches)

bidirectionally

The esophagus functions _ in ruminants, allowing them to regurgitate their cud for further chewing, if necessary.

rumination or chewing the cud

is where forage and other feedstuffs are forced back to the mouth for further chewing and mixing with saliva.

reticulum

This cud is then swallowed again and passed into the _.

rumen

The solid portion left behind in the _ typically remains for up to 48 hours and forms a dense mat, where microbes can use the fibrous feedstuffs to make precursors for energy.

• fermentation

Then the solid portion slowly moves into the rumen for _, while most of the liquid portion rapidly moves from the reticulorumen into the omasumand then abomasum.

75 percent

The ruminant stomach occupies almost _ of the abdominal cavity, filling nearly all of the left side and extending significantly into the right side.

• rumen and reticulum

• omasum

• abomasum

the _ comprise 84 percent of the volume of the total stomach, the 12 percent, and the _ 4 percent.

Rumen

is the largest stomach compartment, holding up to 40 gallons in a mature cow

Rumen

is sometimes called the “paunch.”

Rumen

It is lined with papillae for nutrient absorption and divided by muscular pillars into the dorsal, ventral, caudodorsal, and caudoventral sacs.

Rumen

acts as a fermentation vat by hosting microbial fermentation.

starch and soluble sugar

About 50 to 65 percent of _ consumed is digested in the rumen.

• Methanobrevibacter ruminantium

• Fibrobacter succinogenes

• Ruminococcus albus

• Ruminococcus flavefaciens

• Prevotella ruminicola

Some of the most important microbes in the ruminant stomach

• Cellulose digestion

• Protein metabolism

• Volatile fatty acid production

• Methane production

• They help ruminants extract nutrients from plant-based foods.

• Microbes play crucial roles in:

• Methanobrevibacter ruminantium

A methanogen that produces methane.

• Fibrobacter succinogenes

• Ruminococcus albus

• Ruminococcus flavefaciens

Cellulolytic bacteria that breaks down cellulose

Prevotella ruminicola

A bacterium that breaks down proteins and carbohydrates.

Reticulum

holds approximately 5 gallons in the mature cow.

Rumen and reticulum

are considered one organ because they have similar functions and are separated only by a small muscular fold of tissue.

Omasum and abomasum

hold up to 15 and 7 gallons, respectively, in the mature cow.

Reticulorumen

is home to a population of microorganisms (microbes or “rumen bugs”) that include bacteria, protozoa, and fungi.

volatile fatty acids (VFAs)

These microbes ferment and break down plant cell walls into their carbohydrate fractions and produce _, such as acetate (used for fat synthesis), priopionate (used for glucose synthesis), and butyrate from carbohydrates. The animal later uses these for energy

Reticulum

is called the “honeycomb” because of the honeycomb appearance of its lining.

reticulum

It sits underneath and toward the front of the rumen, lying against the diaphragm. Ingesta flow freely between the reticulum and rumen

reticulum

collect smaller digesta particles and move them into the omasum, while the larger particles remain in the rumen for further digestion.

reticulum

also traps and collects heavy/dense objects the animal consumes.

reticulum

sometimes referred to as the hardware stomach

hardware disease

During normal digestive tract contractions, this object can penetrate the reticulum wall and make its way to the heart, where it can lead to _.

omasum

is spherical and connected to the reticulum by a short tunnel.

Omasum

It is called the “many plies” or the “butcher’s bible” in reference to the many folds or leaves that resemble pages of a book.

Omasum

Water absorption occurs here. Cattle have this as highly developed and large.

Abomasum

is the “true stomach” of a ruminant. It is the compartment that is most similar to a stomach in a nonruminant.

Abomasum

produces hydrochloric acid and digestive enzymes, such as pepsin (breaks down proteins),

Abomasum

receives digestive enzymes secreted from the pancreas, such as pancreatic lipase (breaks down fats).

Abomasum

This has secretions that help prepare proteins for abso rption in the intestines.

3.5 to 4.0

The pH in the abomasum generally ranges from _

chief cells

The _ in the abomasum secrete mucous to protect the abomasal wall from acid damage.

small intestine

is a tube up to 150 feet long with a 20-gallon capacity in a mature cow

7 and 8

Digesta entering the small intestine mix with secretions from the pancreas and liver, which elevate the pH from 2.5 to between _.

small intestine

higher pH is needed for enzymes in the _ to work properly.

Bile from the gallbladder

is secreted into the first section of the small intestine, the duodenum, to aid in digestion.

Large intestine

absorbs water from material passing through it and then excretes the remaining material as feces from the rectum.

Cecum

s a large blind pouch at the beginning of the large intestine, approximately 3 feet long with a 2 gallon capacity in the mature cow.

Colon

is the site of most of the water absorption in the large intestine

acetate

VFA used for fat synthesis

propionate

VFA used for glucose synthesis

butyrate

VFA from carbohydrates.