Byproduct of biodiesel effective in feed
Researchers at Iowa State University and the US Department of Agriculture's
Agricultural Research Services (ARS) discovered that a biodiesel by-product in
pig feed is effective to pigs.
In a growth study, 5 and 10% glycerin was fed to pigs from weaning to market
weight. Results showed equal growth performance between the
glycerin-supplemented diet and a more conventional corn-soymeal
Brian Kerr, an ARS research leader and
collaborating associate professor of animal science, directed the glycerin feed
trials. In the study, both nursery and finishing pigs were fed at levels of 5,
10 and 20% glycerin. These studies showed the glycerin is readily used by pigs
and has an energy value similar to corn.
One problem identified in the
swine metabolism trial is that the diet containing 20% glycerol would not have
flowed well in a dry self-feeder so Mark Honeyman, animal science professor and
coordinator of Iowa State's Research Farms said the 10% inclusion level may be
the upper limit. Bregendahl described the laying-hen diets that included 10 to
15% crude glycerin as 'rather sticky.'
are questions about how glycerin might impact meat quality. The swine project
includes carcass data collection and meat quality evaluations, with those
Another question centers on the fact that when biodiesel is
produced from soybean oil, methanol is used in the process. Methanol can be
toxic, so Honeyman said swine and poultry producers interested in trying
glycerin as part of a feed ration would need to work with the biodiesel plant to
make sure methanol levels are below the Food and Drug Administration (FDA)
approved level of 150 parts per million in the glycerol.
With the rapid expansion of ethanol and biodiesel production
in Iowa, there are questions about possible uses for what remains after these
alternative fuels leave the plant. So far, the use of ethanol by-products in
animal feed has received most of the attention.
Biodiesel often is made from
soybean or vegetable oil, with crude glycerin the resulting by-product. This
compound, which currently is used in such things as hand lotions, cosmetics and
shampoo, is a pure energy source.
increase in biodiesel production comes a surplus of crude glycerin," said
Honeyman. "And with an increase in ethanol comes higher corn prices. Since corn
is fed to pigs primarily for its energy value, we're studying the possibility of
replacing corn with glycerin in swine feed."
Kerr, Honeyman and Bregendahl,
along with other Iowa State researchers, have a series of funding proposals in
the works to further examine the use of crude glycerin in diets for nursery and
finishing pigs, sows, broilers and layers.
Food and Drug
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