Mesquite as a Cattle Feed
Mesquite might serve as a roughage with little nutritional value,
or as an energy cattle feed. Use as a roughage source is the more
simple function, but use as a total energy feed is the more beneficial,
In the latter case, feed grains would not have to be purchased. This
would free the feed grains for human consumption thereby supplementing
man's dwindling food supply (Scott et. al., 1969).
Ruminant animals have four stomachs. Of these, the first three
have the unique ability to digest cellulosic materials which humans
cannot digest. This is possible because these animals have a symbio-
tic arrangement with cellulolytic microorganisms which habitate their
rumen, a first stomach. Thus, the rumen provides ideal conditions for
fermentation, and the microorganisms provide the animal with nutrients
by enzymatically breaking down cellulose and hemicelluloses. Pure
cellulose is completely digestible and thus provides as much energy
as the best feed grains (Scott, et^. ail_., 1969). The fermentation
products which the animal utilizes for energy are primarily acetic
acid and propionic acid. The animals also obtain proteins from the
bacteria and protozoa that pass into the digestive tract. Thus, in
the overall process man gains because materials not suited for human
consumption are converted to usable meat and milk products.
Beef and dairy cattle consume over 400 million tons of feed each
year (Millett, £t. aj_., 1975). In feedlots and dairy farms, the
cattle are fed high carbohydrate grains to promote meat and milk
production. However, some roughage material must be mixed with these
high energy rations or else abnormalities in the liver and stomach
occur (Millett, et^. aj^., 1969). Roughage is also required to physi-
cally stimulate the rumen walls and promote chewing which increases
salivation for the maintenance of rumen pH. Roughage material, such
as grass hay, corn cobs, and cottonseed hulls, can range from $20 to
$40 per ton and are increasing in price (Scott et_. aj_., 1969).
The Texas Agricultural Experimental Station at Spur, Texas, con-
ducted feeding tests on yearling steers to determine the effects of
using mesquite as a roughage. The steers consumed a maximum of 10
pounds of mesquite per day without the addition of molasses. When
molasses was blended into the ration for palatibility, the steers
consumed up to 16 pounds of mesquite per day which represented about
50% of their ration. When mesquite roughage was compared to silage
roughage, the silage-fed steers gained more weight; but, because
mesquite v/as less expensive, the mesquite-fed steers gave an advantage
in net return of $0.32 per head over those fed silage. The mesquite-
fed steers showed no ill effects and the slaughter and carcass data
differed little from that of the control group. This study showed
that the use of mesquite as a roughage is attractive when the price
of conventional roughage is abnormally high (Marion, et^. al_., 1957).
However, research at Texas Tech University concluded that a ration
of ground mesquite alone could not meet the nutritional or energy
requirements for pregnant, lactating beef cows (Ellis, 1969). Al-
though mesquite contains 70% to 75% carbohydrates, a relatively small
percentage of this is digestible due to the protective action of the
lignin (Millett, et^. a\_., 1969). If the digestibility of mesquite
could be increased so that a cow could sustain herself and her calf,
the processed mesquite would have potential for significant utiliza-
tion on ranches. In order to meet these needs, a treatment of mes-
quite would be necessary to make the cellulose more readily available
to the rumen microorganisms. In order to increase the digestibility
of wood, it is necessary to break down the lignin in the cell walls
and to disrupt the structure of the cellulose. Lignin is an amorphous,
polymetric material composed of propyl-benzene units, methoxyl groups,
and hydroxyl groups. It is found in the cell wall along with cellulose
and adds strength and durability to the plant (Cote^ 1965). Lignin is
indigestible and resistant to many microorganisms.