The Importance of Fiber in Deer Diets
Shane Horrocks
M.S.
Wildlife
Nutritionist
MaxRax Wildlife
Nutrition, Inc.
Whitetail
Deer are adapted to utilize fibrous plant material as a daily source of energy
or carbohydrates. Fibrous material is composed of cellulose, hemicellulose,
pectin, and lignin, where hemicellulose and cellulose are the primary sources
of energy. Fiber is broken down in the rumen by enzymes produced by
microorganisms, then converted to energy, proteins, and vitamins. But why feed fiber if you are already
providing the deer with protein, energy, and vitamins?
The
importance of feeding adequate fiber in deer diets (total daily consumption) is
to maintain optimal rumen function. In order to maximize deer production, the
correct concentrations and ratios of protein, energy and fiber must be present
in the diet.
Fiber
must be of good quality and quantity to facilitate rumen health. Crude fiber, or total fiber, is important to
consider, but accurate amounts of Neutral Detergent Fiber (NDF) and Acid
Detergent Fiber (ADF), two different qualities of fiber, must also be
considered and balanced to achieve proper rumen health and accurate use of the
total fiber. Neutral Detergent Fiber is more digestible fiber, while Acid
Detergent Fiber will promote cud chewing. When a deer chews their cud, they are
mechanically breaking down the fiber which allows greater fermentation of the
fiber in the rumen. As fermentation
occurs, acids are constantly produced and secreted into the rumen, which lowers
rumen pH. However, saliva contains an antacid known as sodium bicarbonate, that
balances the acidity of the rumen. Saliva production increases as a result of
more cud chewing, which occurs when accurate amounts of good quality fiber are
present in the diet.
Particle
size is also critical to fiber digestion and utilization. If fiber particle size is small, it is more
easily passed through the rumen and into the intestine. Good fiber should remain
in the rumen long enough to be fermented, which is why supplemental hay and
grass (or natural browse) can be beneficial. Particle size also impacts rumen
muscle stimulation. The rumen tissue is partially comprised of muscle that is
constantly contracting and relaxing, allowing for proper mixing of feed and
hay. When fiber particles rub or scratch the inside of the rumen wall, they
stimulate muscle contraction. Without muscle contraction, feed digestion in the
rumen is reduced and can lead to inefficient bacterial growth.
Additional
benefits from fiber are the production of volatile fatty acids like acetate and
butyrate. Acetate and butyrate are produced from the fermentation of fiber and
are used as an energy sources. During lactation, does can utilize acetate to
produce more milkfat, and acetate is also responsible for the development and
growth of the rumen in fawns, which occurs approximately two weeks after birth.
Butyrate helps to facilitate the growth
of rumen villi responsible for absorbing energy and nitrogen. Butyrate can also
cause the villi in the small intestine to grow in length, which increases the
intestinal surface area available for absorption of nutrients (amino acids,
fat, carbohydrates) from the feed.
Finally,
fiber present in the small intestine can also help to irreversibly bind toxins circulating
in the bloodstream so they are safely excreted in the feces.
A
good quality plane of nutrition for deer always has good fiber quantity and
quality. Deer should always consume appropriate amounts of good quality fiber on
a daily basis. If fiber is not present in the feed, be sure to supplement fiber
in the form of hay or high quality browse/grass. The amount of fiber needed in
the feed on a daily basis will depend on several factors such as animal age,
sex, stage of production, current diet, available browse, and amount of hay
supplemented daily. Consult a wildlife nutritionist to determine appropriate
fiber concentrations in your feed.