There are those who like chili without beans and some poor, misguided souls who prefer chili without meat. The latter choose that option based on ideology and the former out of deference for those who will be spending time with them the next few hours. Yes, beans are a notorious food, but so too can be salads loaded with leafy vegetables. So what's the common denominator? Probably the bigger question in your mind is, “Why in heck is he talking about foods that cause gastrointestinal issues?”
The answer to both
questions is digestibility. These food sources are high in fiber, and our
monogastric stomachs have trouble digesting some of the fiber found in these
types of foods. That's why people with “slow movement” issues are encouraged to
eat more fiber. A large part of the fiber component is not digested and passes
quickly through the system. Aside from those types of issues, people often shy away
from particular types of food that “don't agree with them.” There can be
multiple reasons why a particular food doesn’t sit well on someone’s stomach,
but in many cases, it boils down to that person’s inability to properly digest
it. The title of this article is a fairly bold statement. After all, nearly every
food plot product touts the protein level or some other nutrient level that the
product can provide. Without question, nutrient level is extremely important,
but if a deer cannot digest the food source or can only digest a small portion
of it, nutrient level becomes obviously less beneficial. Let’s say, for
example, that a food plot is providing 25 percent protein and that food plot
will make up about two pounds of the deer’s daily intake. That equates to about
0.5 pounds of protein provided by the food plot. Now let’s say that the food
plot has a digestibility level of only about 50 percent. The protein amount the
deer is actually using is 0.25 pounds. Let’s say you have a food plot that provides
20 percent protein but is 70 percent digestible. If the deer eats the same
amount of the food plot, that deer will receive 0.28 pounds of protein. So even
though the protein level is lower, the digestibility level offsets it, and the
total protein the deer uses is greater. Keep in mind that these are just
arbitrary numbers, but they illustrate the point that digestibility must be
considered along with nutrient level.
The Rumen Bear with me in this section as I get deep into the science of digestibility.
To understand digestibility, you first have
to understand how a deer’s digestive system works. Deer are ruminant animals. What
this means is their stomach is comprised of multi-chambered sections including
the reticulum, omasum, rumen and abomasum. Of these four, the rumen comprises
the largest portion and is the core of a deer’s digestive system. When you are
field-dressing a deer and accidentally cut into the grayish balloon-like thing
and aroma springs forth, you have found the rumen. The rumen is a large
fermentation sack that is home to millions of microbes. The microorganisms
depend on the deer as a host, and the deer depend on the microorganisms to break
down food into nutrients that can be digested and used by the deer. This is
called a symbiotic relationship, meaning that each party is dependent on the
other. The two largest groups of microbes are bacteria and protozoa. Bacteria
can be broken down into cellulolytic bacteria, which degrade cellulose;
hemicellulolytic bacteria, which degrade hemicellulose; amylolytic bacteria,
which degrade starches; proteolytic bacteria, which degrade proteins; and
lipolytic bacteria, which degrade lipids, or fat. Protozoa can be grouped into
two categories: ciliate and flagellate protozoa, with the majority of rumen
protozoa falling under the ciliate group. Protozoa species specialize in the type
of nutrient they degrade and use, much like bacteria. The rumen environment is
typically not static and shifts in the population amounts of the types of
bacteria and protozoa, with these changes often caused by the food sources
being consumed by the deer. If a deer has a predominantly fiber-based diet,
cellulolytic bacteria will be abundant. If starches such as grains become a
large portion of the overall diet, amylolytic bacteria will increase, and the
percentage of other bacterial types will decrease. This decrease is caused by
amylolytic bacteria proliferating more because of starch availability and also
a slight drop in pH, which does not favor cellulolytic bacteria. For a deer to
be healthy it must have a healthy rumen microbial population that can break
down the food that deer consume. It is common and even natural for rumen
microbial populations to shift slightly. It is only when dramatic shifts occur
that significant problems might arise.
Browsers vs. Grazers
With all of those critters in a deer’s rumen,
you might think they could digest about any forage. Although they can digest
many types of forage, the digestibility range of deer is rather small. Deer are
small ruminants compared to cattle, which are considered a large ruminant. There
is really nothing scientific in the classification. It simply means that one
has a small rumen and the other a large rumen. A larger rumen equates to more
surface area and more papillae, which are finger- like protrusions that cover
the rumen wall and are the home of the microbial colonies. The more surface
area and papillae, the larger the microbial population can be and the more
effect fermentation can have on a wide range of forage types and qualities. Cattle
fall under the classification of grazers, which means they non-selectively consume
vegetation. Before anyone cries foul, yes, cattle select food sources to a
certain degree. However, compared to small ruminants, cattle are non-selective
and graze along with their wide muzzles, eating grasses, forbs, grains and
whatever happens to be in front of them. Deer, on the other hand, are considered
browsers or concentrate selectors. That means they will pick and choose the
food they consume. They might walk past lush grass to get to a clover field or
even walk past one clover field to get to another. They might pick the leaf off
of a plant but not eat the stem. And they might browse in a food plot, eat some
acorns and then go pick at some standing corn, all within 30 minutes. The
primary reason for this type of eating behavior is that with a small rumen,
they have to pick and choose the type of vegetation or the particular part of a
plant they can digest. Because deer have limited fermentation capability as
compared to a large ruminant, the leaf off a plant might be much more
digestible than the stem (and normally is), so they pick off the leaf and leave
the rest. A couple of examples are kernels of corn versus the rest of the plant
and alfalfa leaves as opposed to the stems. You can grind up the corn, cob and
the stalk and feed it to cattle, and they will do well with it, or you can feed
a bale of alfalfa hay to cattle, and they will eat leaf, stem and all. Feed the
same to deer, and they will pick out the kernels of corn and the alfalfa leaves
and leave the rest. Further, deer might ignore a food source until each reaches
a growth phase when it becomes more highly digestible. You might ask, “Doesn’t
taste play a role in preference?” To a certain degree, yes, but is the taste
preference a reflection of digestibility? I don’t know, but it's interesting
that you rarely see deer eat anything they can’t digest unless there is no
other food available.
Food Plots and Digestibility
So how can you apply any of this information
to your food plot program? If your food plot program is designed to improve the
herd through nutrition and/or to attract deer, you must consider the
digestibility of what you are planting. Spring, summer and early fall are critical
times for quality nutrition for your deer herd, as this is when nutrient
demands are highest. Does are in lactation and using huge volumes of nutrients
such as protein, energy and minerals to produce nutrient-rich milk to raise
fawns. If you have ever seen a doe milking twins or triplets in July, you
probably notice that her body condition looks poor, and she appears gaunt and
sunken in. A high-quality food source that provides needed nutrition will help her
raise large, healthy fawns and will also supply enough nutrients for her to
help maintain body condition. Bucks are in the heart of antler growing season
in spring and summer and, similar to does, have the highest nutrient demands
during this time. Sixteen to 18 percent protein is needed for bucks and does to
achieve maximum production efficiency. To supply these needed nutrients for
this time of year, my go-to food plots are legumes such as clover and/or alfalfa.
Further, I prefer perennial varieties to help ensure the food source is there
immediately upon spring green-up and lasts well into fall. But just using any
type of clover or alfalfa will not necessarily achieve the best possible
results. Digestibility needs to be considered, which is why for many years my
perennial legumes of choice have been Imperial Whitetail Clover and Imperial
Alfa-Rack Plus. The Whitetail Institute developed Imperial Whitetail Clover
with deer in mind, which is important, as it has characteristics different from
most clovers varieties on the market. Most clover varieties were designed for
hay production for cattle pasture mixes. If you remember our discussion about
the difference between cattle and deer, cattle have the ability to digest
mature, thicker-stem vegetation. A hay variety clover or even most pasture clovers
were designed for fast growth and to produce large quantities. To accomplish
this, these clovers typically are comprised of a heavy stem to support the
rapid growth and to mature quickly for harvesting. On the other hand, Imperial
Whitetail Clover was designed to have a very thin stem and a larger leaf. What
this means is that digestibility for deer is much higher, which improves the
attractiveness and the utilization of the food plot. Similarly, Imperial
Alfa-Rack Plus was designed using a specific grazing alfalfa that is more
slow-maturing, thin stemmed and heavy-leafed than hay varieties, making it more
digestible and attractive. These are the reasons thousands of users of these
products report seeing deer walk through other food sources to get to Imperial
Whitetail Clover and/or Alfa-Rack Plus. A good illustration of this is watching
an alfalfa hay field after it has been cut for hay. New, tender growth sprouts,
and deer activity on the field is high. As the days pass and the plants grow
and mature, activity becomes increasing less as digestibility drops.
Conversely, with Alfa-Rack Plus using slow maturing alfalfa, deer activity
remains high and constant. Digestibility must also be considered for fall and
winter food plots. Because fall and winter food plots consist of mostly
annuals, you need to consider what and when you plant to match it with when you
want the deer to use those plots whether it is for nutrition or hunting or both.
My fall plots are primarily brassicas, winter wheat and cold hardy oats. Oats
like those found in Whitetail Oats Plus and Imperial Pure Attraction are highly
palatable and digestible, especially during their growing or vegetative stage.
I live in Iowa, so I plan my plantings of these forage types in early
September, with the goal of having the plants about four to six inches tall
when bow season starts the first of October. This maximizes attractiveness and
the amount of food available. When the temperatures drop below freezing and
cold winter weather sets in, I turn to my brassica plots. I plant my brassicas
in late July or early August to allow for plenty of time before a frost
inhibits growth. I like to use a brassica variety such as Imperial
Winter-Greens and/or Tall Tine Tubers that contain tuber varieties, as it will
give deer the green tops of the plants and provide highly digestible tubers that
deer use throughout winter.
Conclusion
If you are throwing a dinner party and want
people to show up, soybean husks, ground corn cobs and salad rich in woody
plants would probably not be the best choice. That is unless everyone coming
suffers from constipation. Instead, you will want to serve good-tasting foods that
do not cause digestive problems. In the same way if you want deer to use your
food plots and want to supply your deer with the nutrients they need and can
digest, you must consider digestibility.
