Beef Cattle Nutrition and Feeding
Frequently Asked Questions
Whole versus Chopped or Ground Corn as an Energy Source
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Corn is one of the most commonly used grains for supplementing energy
deficiencies in beef cattle diets. Whole corn is generally cheaper per ton than
cracked, rolled or ground corn because of the added cost associated with grain
processing. In addition, some cattle producers have the opportunity to purchase
corn directly from farmers after harvest or plan to purchase bulk loads of whole
corn or corn screenings.
Most cow-calf operations do not have grain processing and mixing equipment.
For this reason, the question often arises as to whether certain grains can be
fed whole or do they need to be processed. This question arises from the fact
that whole grains can be seen in the fecal patties, alerting the producer that
the animal may not be getting the nutrients out of the grain.
In theory, processing grain should improve the digestibility and feed
conversion of a feed by (1) reducing particle size that allows for more sites of
attachment for rumen microbes and (2) some processing methods change the
structure of the starch rendering the feed grain more digestible. However, as
previously stated, further processing always comes with additional cost, and the
improvement in grain digestibility and feed conversion must outweigh the cost
for additional processing.
Corn is one grain that can be fed whole when it is being used a supplement. A
study conducted at the University of Arkansas in the early 90's reported no
difference in the growth performance of steers grazing bermudagrass pasture and
supplemented with either whole or ground corn at one percent of body weight over
an 84-day grazing period.
Researchers in Canada evaluated the effects of chewing on the digestibility
of whole grains when fed to cows at one percent of body weight. They found that
chewing during ingestion and rumination resulted in extensive damage to corn
kernels. The damage that occurred to the corn kernel during these processes
would help support the idea that cattle supplemented with whole corn might
perform similarly to cattle fed chopped corn. They also noted that the whole
grain observed in the feces appeared to be greater than what was actually
present. Interestingly, eleven percent of the kernels that appeared to be whole
in the feces were actually empty inside, indicating minor damage to the whole
kernel made the starch within the kernel accessible to rumen microbes and
digestive enzymes.
Researchers in Ohio collected the corn kernels excreted daily from cows fed a
forage diet and supplemented with corn at 0.3% body weight or fed at high corn
ration where corn intake was at 0.8% body weight. From determining the amount of
kernels fed and collecting the whole kernels in the feces, these researchers
found that 88% of the kernels fed had been digested.
The effects of processing corn extends beyond supplements to feeding high
levels of corn in high concentrate rations similar to those used in bull test
rations and finishing rations. A review of processing methods on average daily
gain and feed conversion revealed that cattle gained at a similar rate (3.19 lbs
per day) among studies where whole corn was fed as compared to dry rolled corn.
Feed conversion (pounds of feed required per pound of gain) were significantly
lower with whole corn (5.95 lbs) as compared to dry rolled corn (6.57 lbs) as a
result of cattle fed whole corn consuming nearly 2 lb less per day than cattle
consuming dry rolled corn. However, the authors noted that this may also be an
artifact of finishing diets with whole corn generally contains less roughage as
compared to finishing diets with processed corn.
Although dry rolling and cracking have not consistently improved animal
performance, this assumption is not the same for corn that has been exposed to
steam prior to rolling. Processing corn in this manner, generally termed "steam
rolled" or "steam flaked," alters the structure of the starch within the grain
through a process called gelatinization. Steam, unlike dry processing methods,
significantly improves the metabolizable energy content of corn.
Processing corn may become necessary when small amounts of additional
ingredients such as protein feeds (e.g. soybean meal), mineral and vitamin
premixes, or feed additives are going to be blended with the corn. Mixing large
quantities of whole corn with minute amounts of other feedstuffs or feed
additives will result in the blend becoming unevenly distributed due to sifting
of the smaller feed particles during shipping and handling.
Although corn can be fed whole as a supplement, this concept cannot be
applied to all feed grains. Some feed grains contain a hard external coat. Feed
grains that benefit from processing before feeding include rice, sorghum and
wheat. Since there is a slight reduction in digestibility associated with
feeding whole corn, an energy value of 88% total digestible nutrients, or TDN
(dry matter basis) if often used for formulating diets with whole corn, as
compared to 90% TDN for cracked corn.
Cracked corn can be seen on the left with whole corn on the right. |
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