The document summarizes the anatomy and functions of the ruminant digestive tract. It describes the four compartments of the ruminant stomach (rumen, reticulum, omasum, and abomasum) and explains their roles in fermenting feed, absorbing nutrients, and breaking down material. Key functions of the rumen like microbial fermentation of fibers into volatile fatty acids and belching of gases are also outlined. Common digestive disorders like bloat and acidosis are briefly discussed.

1. Diseases of the Ruminant digestive
tract
Dr Karima Al Salihi

2. Anatomy of bovine digestive tract
Quick facts
• Ruminant stomachs have four
compartments: the rumen, the
reticulum, the omasum and the
abomasum.
• Rumen microbes ferment feed
and produce volatile fatty acids,
which is the cow’s main energy
source.
• Rumen microbes also produce
B vitamins, vitamin K and
amino acids.

3. The digestive tract of the adult cow
The cow's digestive tract consists of the following.
• Mouth
• Esophagus
• A four-compartment stomach, which
includes
◦ The rumen (paunch)
◦ The reticulum (“honeycomb”)
◦ The omasum (“manyplies”)
◦ The abomasum (“true stomach”)
• Small intestine
• Large intestine

4. Stomach comportents
1. The rumen
The rumen (on the left side of the animal) is the largest stomach
compartment and consists of several sacs. It can hold 25 gallons or
more of material depending on the size of the cow. Because of its
size, the rumen acts as a storage or holding vat for feed.
Aside from storage, the rumen is also a fermentation vat. The
rumen’s environment favors the growth of microbes. These microbes
digest or ferment feed within the rumen and make volatile fatty acids
(VFAs). The rumen absorbs most of the VFAs from fermentation.
A good blood supply to the rumen walls improves absorption of VFAs
and other digestion products. Tiny projections (papillae) line the
rumen, which increases the rumen’s surface area and the amount it
can absorb.

5. 2. The reticulum
The reticulum is a pouch-like structure in the forward area of the body, close to the
heart. The tissues in the reticulum form a network similar to a honeycomb. A small
tissue fold lies between the reticulum and rumen, but the two aren’t separate
compartments. Together they’re called the rumino-reticulum.
Heavy or dense feed and metal objects eaten by the cow drop into this compartment.
Nails and other sharp objects may work into the tissue and cause “hardware disease.”
You can use magnets to prevent disease or correct the problem through surgery.
Leaving it untreated may lead to infection and possibly death.
3. The omasum
The omasum is a globe-shaped structure containing leaves of tissue (like pages in a
book). It absorbs water and other substances from digestive contents. Feed material
(ingesta) between the leaves will be drier than ingesta found in the other compartments.
4. The abomasum
The abomasum is the only compartment lined with glands. These glands release
hydrochloric acid and digestive enzymes, needed to breakdown feeds. The abomasum
is similar to a nonruminant stomach.

6. The small intestine
• The small intestine consists of three sections:
the duodenum, jejunum and ileum.
• It measures about 20 times the length of the
animal.
• Secretions from the pancreas and gallbladder
aid in digestion within the small intestine.
• The small intestine completes most of the
digestive process and absorbs many nutrients
through villi (small finger-like projections).
• From the villi the nutrients enter into the blood
and lymphatic systems.

7. Cecum
The cecum is the large area
where the small and large
intestine meet. The cecum
breaks down some
previously undigested fiber,
but the exact importance of
the cecum remains unknown.

8. Large intestine
The large intestine is the last section
of the tract that undigested
feedstuffs pass through. Microbes
digest some undigested feed here,
but the main digestive function of
the large intestine is to absorb
water.

9. Digestive tract functions
1. Belching ( eructation)
Digestion produces 30 to 50 quarts of gas per hour in the rumen. Carbon dioxide and
methane are the main gases present. Cows must release this gas to avoid bloating. Under
normal conditions, swelling from gas formation causes the cow to belch and release the gas.
2. Rumination
Cows may spend 35 to 40 percent of each day ruminating (cud chewing). The amount of
time spent ruminating depends on the diet. Little ruminating occurs when cows eat grain or
finely ground rations. But when eating long hay, cows may ruminate for several hours.
Mature cattle spend little time chewing while eating feed. Thus,
during rest periods, cows regurgitate (bring up) soft feed wads
(cud) to re-chew and break into smaller pieces. They also re-
salivate the feed and re-swallow it. This process makes the feed
easier for the microbes to digest.

10. 3. Feed movement in the rumen
The rumen contracts and moves continuously. Healthy cows
have one to two rumen contractions each minute. Poor rumen
movement may indicate a sick animal.
When the rumen contracts it
• Mixes contents
• Brings microbes in contact with new
feedstuffs
• Reduces flotation of solids
• Moves materials out of the rumen

11. 4. Saliva production
A cow’s salivary glands can make and add 50 to 80 quarts
of saliva to the rumen daily. Saliva has several functions
in cows.
• It provides liquid for the microbes.
• It recirculates nitrogen and minerals.
• It buffers the rumen.
◦ Saliva keeps the rumen pH between 6.2 and
6.8 for best digestion of forage and feedstuffs.

12. 5. VomitingCattle rarely vomit.
Sometimes certain feeds will
induce vomiting. A few pasture
plants, usually weeds, contain
compounds called alkaloids
that can cause vomiting. Work
with a veterinarian if this
problem continues.

13. 6. Energy feed digestion in the rumen
Rumen microbes digest simple and complex carbohydrates (fiber)
and convert them into VFAs. VFAs mainly consist of acetic,
propionic and butyric acids and provide 50 to 70 percent of the
cow’s energy.

14. Diet can affect the amounts of each VFA microbes produce.
• High forage diets result in more acetic acid forming (60 to 70
percent of total) than propionic (15 to 20 percent) and butyric
acids (5 to 15 percent).
• More grain or finely ground forages can cause the amount of
acetic acid to decline to 40 percent, while the amount of
propionic acid may increase to 40 percent.
Such changes in VFA production usually relate to a
reduction in milk fat test.
Microbes digest about 30 to 50 percent of the fiber
units, cellulose and hemicellulose, in the rumen. Sixty
percent or more of the starch is degraded depending on
the amount fed and how fast ingested materials move
through the rumen. Most sugars get completely
digested within the rumen.

15. VFAs absorb into the bloodstream from the
rumen and move to the body tissues
including the udder. Once in the tissues, the
cow uses VFAs as a source of energy for
• Maintenance
• Growth
• Reproduction
• Milk production

16. Protein and nonprotein nitrogen use in
the rumen
Not all consumed proteins get broken
down in the rumen, (see figure 2).
Through fermentation, protein is
converted to ammonia, organic acids,
amino acids and other products. About
40 to 75 percent of the natural protein in
feed gets broken down.

18. The amount of breakdown depends on many factors including:
• The ability of the protein to dissolve
• How resistant the protein is to breakdown
• How fast the feed passes through the rumen
Aside from protein breakdown, nonprotein nitrogen (NPN) sources
also provide ammonia. NPN sources include urea, ammonium salts,
nitrates and other compounds. Many rumen microbes need ammonia
to grow and build protein. Rumen microbes convert ammonia and
organic acids into amino acids to use for building protein.
Most of the extra ammonia absorbs into the bloodstream from the
rumen. But small amounts may pass into the lower digestive tract and
absorb there. Feed protein (not broken down in the rumen) and
microbial protein pass to the abomasum and small intestine for
digestion and absorption.

19. Vitamin Production
Rumen microbes make vitamin K and all
B vitamins. Microbes make enough of
these vitamins for cattle growth and
maintenance. Thus, under most
conditions, cattle with healthy rumens
don’t need added B vitamins or vitamin K
in their diet. Cows under stress may need
added niacin (B3) and thiamine (B1).

20. Fat digestion
Most fat digestion and absorption occurs
in the small intestine. Cows absorb more
saturated fat than simple-stomach animals.
This is because rumen microbes change
unsaturated fatty acids to saturated fatty
acids by adding hydrogen molecules.
Feeding a lot of unsaturated fatty acids
can be toxic to rumen bacteria, slow fiber
digestion, and lower rumen pH.

21. Calf digestive system
The rumen, reticulum and omasum
remain undeveloped at birth and during
the first few weeks of life. The calf’s
largest stomach compartment is the
abomasum. At this stage of life, the
rumen doesn’t function and thus some
feeds that mature cows can digest,
calves can not.

22. Esopageal groove
During nursing or bucket feeding milk
bypasses the rumen and directly enters
the abomasum via the esophageal
groove. Reflex action (e.g. when the
calf nurses) closes the groove to form a
tube-like structure. This prevents milk
or milk replacer from entering the
rumen. If the calf drinks milk rapidly,
some may overflow into the rumen.

23. Rumen development
The rumen will remain undeveloped as long as the calf
stays on milk. Once the calf begins eating grain and
forage, a microbial population will develop in the rumen
and reticulum. The end products from microbial
fermentation are responsible for developing the rumen.
Calves don’t need cud inoculation to start rumen
development.
Feeding grain with or without forage during the first few
weeks of life will result in larger and heavier papillae
growth in the rumen. Thus, the rumen will begin
functioning like the adult’s when the calf is three months
old.

24. Diseases of the Digestive System
1. Bloat ( Tympany).
Bloat is the accumulation of free gas or froth in the rumen. Bloat is less common in small ruminants
than in cattle, and it occurs less frequently in goats than in sheep. Bloat can occur from ingesting
diets such as high-legume diets or cereal grains that promote the formation of froth in the rumen.
Some diets, again such as those high in grain, promote the formation of free gas. Sometimes an
animal will have an accumulation of free gas in the rumen because of a failure to eructate.
CLINICAL SIGNS
• Abdominal distension, especially apparent in the left paralumbar fossa
• Signs of abdominal pain
• Anxiety
• Respiratory distress
DIAGNOSIS
• Observation of obvious abdominal distension
• In the case of free gas bloat, a “ping” can be heard in the left paralumbar fossa
• If an orogastric tube is passed, free gas can be heard (and smelled) escaping through the tube.
Frothy bloat will result in froth being seen on the tube.
TREATMENT
• Bloat is an emergency situation and requires immediate attention
• Passage of orogastric tube
• Diocctyl sodium succinate (DSS), mineral oil, vegetable oil for frothy bloat
• Trocarization of the rumen
• Rumenotomy

25. RUMEN ACIDOSIS
Rumen acidosis is caused by the rapid fermentation of highly digestible carbohydrates. The problem occurs more often
with finely ground grains because the bacteria can more rapidly ferment the carbohydrate. The condition is more
commonly seen in animals that have been fed a primarily forage-based diet, and then have received a large amount of
concentrate feed. As the carbohydrates are digested, the pH declines. The decline in pH causes the normal resident
microfauna and flora of the rumen to die. Water is drawn into the rumen, and the animal becomes dehydrated and may
die. The acid buildup causes damage to the rumen epithelium. This allows the leakage of bacteria into the system, and
the animal may become septic.
CLINICAL SIGNS
• Vary with the amount and type of feed
• Signs first appear from 12 to 36 hours after ingestion of feed
• Signs include shock, anorexia, weakness, depression
• Severe dehydration
• Signs of sepsis
• Diarrhea
DIAGNOSIS
• Examination of rumen fluid shows the following:
pH < 5.5
Protozoa reduced in number
Large, Gram-positive rods
TREATMENT
• Treatment is aimed at reversing hypovolemia and shock, removing offending feedstuffs, and correcting the acidosis
and sepsis
• Intravenous (IV) fluids containing sodium bicarbonate
• Flunixin meglumine
• Rumenotomy to remove feedstuffs
• Transfaunation of rumen microflora
• Thiamine subcutaneously (SQ)

26. DIARRHEA
Diarrhea involves loose to runny
feces, and it is defined as the increase
in the volume and frequency of
defecation. Dehydration and
electrolyte imbalances are the
concerning sequelae to diarrhea,
especially in very young kids and
lambs. Animals of certain ages are
more prone to specific infectious
causes of diarrhea

28. Enterotoxigenic Escherichia coli
Enterotoxigenic E. coli causes diarrhea mainly in neonatal lambs and, to a lesser extent, in kids. This type of
bacteria has two main methods by which it causes disease. The first is by attachment and colonization of the
intestinal villi. As these villi are destroyed, the intestine loses its absorptive capabilities. The second method
is by production of an enterotoxin, which interferes with normal gut function. E. coli causes disease in
young animals younger than 10 days, with 1 to 4 days of age being the most common age of onset.
CLINICAL SIGNS
• Usually presents as an outbreak, rather than in a single animal
• Diarrhea
• Dehydration
• Recumbency
• Many animals die before development of diarrhea
DIAGNOSIS
• Fecal culture and serotyping for K99 and F41 antigens
• Histopathology from necropsy confirms
TREATMENT
• Fluid therapy: PO, IV, SQ
• Antibiotics (amoxicillin, ampicillin, neomycin, trimethoprim/sulfa [TMS]) may be beneficial, but may
also kill off beneficial gut flora
• Flunixin meglumine