AVS-4100 Study Guide - Midterm Guide: Hindgut Fermentation, Abomasum, Omasum

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Compiled Notes for Exam 4
16 Cow Behavior
What are cattle?
o Cattle are:
Herbivores ruminant; which means their natural diet
consists mainly of plant materials and their stomach
composed of 4 compartments
Reticulum, rumen (largest and most important),
omasum, and abomasum
o Microbial fermentation normally happens in
the rumen and the reticulum
o Enzymatic digestion happens only in the
abomasum
o
In horses: hindgut fermenters most of the
microbial fermentation of the food/fibers happen in
the large intestine, which is why they have a large
intestine composed of a very large cecum and colon
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o Enzymatic digestion happens in stomach and
small intestine
The rumen which is the largest compartment acts as a
fermentation chamber that breaks down cellulose and
allows them to digest plant materials such as grass,
grains, and husks
Rumen perform 1-3 cycles of contractions per
minute
Size of rumen is ~49 gallons, size of reticulum only is
around 4 gallons
High producing dairy cow needs to eat around 110
to 120 pounds of wet feed per day or 50-55 lbs of
dry matter (roughly 30 lbs of hay and 25 pounds of
grain mix)
Need to drink ~39 gallons of water a day
Rumen contains microorganisms: bacteria, protozoa,
archaea, and fungi
o Microbial Population depends on the quality of
the forage and the amount of grain in the diet
Role of rumen microorganisms
o Fiber digestion
o Production of VFAs
o Breakdown of nutrients
o Methane production
Rumen contains a large amount of rumen projection
called rumen papillae. The main function of this is to
increase the surface area of food digestion and
exposure to microbes
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o The microbes in the rumen will break down
the feed into volatile fatty acids and microbial
protein and also produce hydrogen and carbon
dioxide that usually bind together to form
methane. This results in 3 layers in the rumen:
Liquid bottom layer which is the
digestive food that will be transferred to
the omasum and then the abomasum
A middle solid level which contains
today’s food that is still in digestion
Upper layer of gases that needs to be
expelled through ruminal activity
Expelling the gas eruptation
Ingestive Behavior
o Feeding mechanism: rely for food intake on the high mobility of
the tongue, which is used to encircle a patch of grass and then
to draw it into the mouth, where the lower teeth and the
tongue are used to hold the bound grass while it is broken by a
head movement
Cattle have only 4 pairs of incisors at the lower jaw and a
dense fibroelastic tissue (dental pad), in the upper jaw
used as a grinding surface, the upper lip is not movable
o this is why? the nature of a cow’s eating process is such that it
is virtually impossible for the animal to take pasture plants
closer than 1 cm from the ground
o why have the upper incisors been lost in ruminants?
Scott and Janis (1993) suggest this happened in parallel
with the lengthening of the ruminant jaw, tongue, and
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