Rumen Function and Microbiology
Shane
Horrocks M.S.
Wildlife
Nutritionist
MaxRax
Wildlife Nutrition
Whitetail Deer, like other ruminant animals, have a stomach
with four compartments: the rumen,
reticulum, omasum and abomasum. The
rumen is the largest compartment with a volume of approximately 1.85 gallons in
a 225lb deer, and it maintains a pH between a 6 and 7.2 depending on feed, age
and season. It serves as a storage site for ingested feed that is later
regurgitated and re-chewed and as a fermentation vat for the production of volatile
fatty acids (primary energy source in ruminants). The micro environment is capable
of producing proteins and vitamins (B, and K) and it houses a large, diverse
microbial population (beneficial bacteria, protozoa and fungi). The rumen is
comprised of a muscle layer that contracts and relaxes to assist the mixing of
ingested feed, which allows microorganisms to attach to and utilize swallowed feed
particles. The muscle layer also assists with regurgitation of feed for further
mastication and passage of feed material out of the rumen and eventually into
the intestines. The inner wall of the rumen is made up of specialized
epithelial tissue responsible for absorbing volatile fatty acids produced in
the rumen and nitrogen from plants. Volatile fatty acids are eventually used as
energy and the nitrogen is eventually recycled to the rumen via the saliva to
be assimilated into more rumen microorganisms and protein for the deer to use. Consistency
of rumen function is critical to overall animal health. Indicators like pH level, microbial density,
and nutrient quality and quantity must be optimal to achieve desired animal
performance.
Factors like diet, stress level, and a healthy rumen
microbial population contribute to the efficiency of the rumen and its ability
to produce nutrients for the deer. Microorganisms are needed to produce energy,
proteins and vitamins essential for proper tissue growth, reproduction, and
lactation. When a deer consumes hay or grain, the beneficial microorganisms in
the rumen will ferment the fibrous (cellulose and hemicellulose) portions of
the grain and produce energy products called volatile fatty acids. Volatile
fatty acids are made into sugars, like glucose, which are then used to sustain
the deer’s energy needs. Microorganisms can also utilize non protein nitrogen
from the grains or hay to reproduce and make microbial proteins, which are
critical components of rumen microorganisms. Microorganisms that are passed out
of the rumen and into the deer’s intestine are digested and the protein from
the cells are absorbed just like protein from soybeans or alfalfa. The deer can
then use the microbial protein to meet some of their daily protein
requirements. For this reason, ruminant feeds are specifically developed and
balanced to maintain optimal amounts of protein, non protein nitrogen, and
carbohydrates that can be used for efficient production and turnover of rumen
microorganisms.
High quality, well
balanced feeds can improve rumen health by promoting a diverse microbial population
capable of utilizing carbohydrates, proteins, and fatty acids, and can decrease
potential rumen problems. For example, as carbohydrates (fibrous and
non-fibrous) and proteins are utilized by the microorganisms in the rumen, gases,
such as carbon dioxide and methane, will be produced. A healthy functioning rumen
is capable of expelling these gases; However, unbalanced diets, like high grain
or high legume diets, or the use of drugs can impact the rumen’s ability to
function correctly and inhibit the deer’s ability to release the gases. Grain
overload in ruminant diets can alter the rumen microbial population many ways. Some
grains utilized by rumen microorganisms will produce lactic acid. If a ruminant
consumes too much of a particular grain, like corn, a high amount of lactic
acid will be produced causing a drop in rumen pH. An acidic rumen environment can
kill microorganisms, like fiber degrading organisms, because they are unable to
survive under highly acidic conditions. Consequently, cell death can create an imbalance
in the microbial population and lead to lactic acidosis. Acidosis can destroy
the epithelial tissue responsible for absorbing nutrients through the rumen
wall and into the blood stream. Other problems that can occur with an unbalanced
microbial population are bloat (acute or chronic) and reduction or elimination
of B vitamin synthesis (which can cause blindness) within the rumen. These
potential health threats can all be avoided by feeding a sound and balanced
daily feed. A good quality feed has safe concentrations of soluble
carbohydrates (starch), adequate levels of fiber, and is well balanced to
provide accurate levels of ingredients to not only the animal consuming it, but
also the microbial population living in the rumen.
