BYPRODUCTS FROM ENERGY PRODUCTION FOR SWINE
There is considerable interest in the production of
energy from corn (ethanol) and fat (biodiesel). These
processes yield byproducts that may have a place in
swine nutrition. This article will briefly evaluate recent
research on glycerol and dried distillers grains with
solubles (DDGS) which result from biodiesel and
ethanol production, respectively.
Crude Glycerol
The production of biodiesel involves the
separation of glycerol from fat or oil, a process called
transesterification. The end products of this process are
methyl esters, or biodiesel, and glycerol. Typically, oils
or fats are reacted with alcohols (usually methanol)
in the presence of a catalyst (sodium or potassium
hydroxide) and converted to ethyl esters and glycerin.
The yield of this process is approximately 86 percent
biodiesel, 9 percent glycerin, and 4 percent alcohol.
The co-product glycerin can be used in the
manufacturing of soap s and other products. However,
it also has potential value for the use in swine diets.
Crude glycerol from biodiesel production contains
approximately 85 percent glycerol, 10 percent water,
and 3 to 7 percent salt. The gross energy value ranges from 3600 to 3750 depending on its purity) pure
glycerol contains 4305 kcal/kg gross energy).
Studies in finisher pigs have shown that glycerol
is highly palatable and improved feed intake was
observed with 10% supplemental glycerol without
effects on daily gain (Kijora, 1996; Kijora et al., 1995,
1997; Mourot et al., 1994). Kuhn (1996) reported that
10 percent technical rapeseed glycerol could be fed to
finishing pigs without affecting growth performance.
However, an increased proportion of saturated fatty
acids in the body fat was observed in pigs fed glycerol.
Most recently, Lammers and coworkers (2007)
reported results from a study published at the Midwest
American Society of Animal Science meetings. They
studied the digestible energy value of crude glycerol in
weanling pigs and finishing pigs. Crude glycerol was
added to the diets such that glycerol concentrations
were 0, 5, 10, and 20 percent. The apparent digestible
energy value (DE) of crude glycerol was 3386 kcal/kg
for nursery pigs and 3772 kcal/kg for finishing pigs.
They reported that these values were not different from
the GE of the crude glycerol examined (3625 kcal/
kg for the product they used), which indicated that
glycerol is highly digestible. They further reported that
the metabolizable energy (ME) content of glycerol in nursery pigs, but not finishing pigs, depended on
the level of glycerol that was fed . As glycerol level in
the nursery diet increased, ME content of the glycerol
decreased, indicating increased loss of energy (in this
case from glycerol) in urine with increasing dietary
glycerol. The authors concluded that the ME value for
crude glycerol when included at 0 to 10 percent was
3463 kcal/kg for nursery pigs and 3081 kcal/kg in
finishing pigs when included up to 20 percent.
Dried Distillers Grains with Solubles (DDGS)
A summary of research with DDGS in swine was
recently published by Dr. Hans Stein in Volume 30,
No. 1 of Swine News. Since then, several other studies
were reported at the Midwest American Society
of Animal Science meetings, recently held in Des
Moines, IA. One of these studies (Feoli et al., 2007")
evaluated the DE content of DDGS obtained from
either corn or sorghum. Diets consisted of a reference
diet containing 97.5 percent corn with added vitamins,
minerals, and amino acids . The test diets contained
either one of two sources of corn-based DDGS or one
of two sources of sorghum based DDGS and replaced
50 percent of the corn in the reference diet. The
measured DE content of corn-based DDGS were 3,628 and 2,940 kcal/kg for the two different sources and 3,205 and 2,918 kcal/kg for the two different sources
of sorghum based DDGS. The authors concluded that
both substrate used in the ethanol production process
and the plant from which the DDGS was derived
greatly affect the digestible energy content of DDGS.
In a subsequent study (Feoli et al., 2007), these
researchers used the DDGS from corn with high and
low DE (as obtained in the previous study) and the
DDGS from sorghum with the highest DE in a growth
performance study . They used 11 pigs per pen and 4
pens per dietary treatment. The three sources of DDGS
were included at 40 percent in a corn-soybean meal
based diet and the impact on pig performance was
evaluated compared to a control without DDGS. Their
research showed decreased average daily gain in pigs
fed the DDGS based diets compared to the control.
In addition, pigs fed the corn-based DDGS with high
DE content had reduced daily gain and feed intake,
but better feed efficiency compared to the other two
treatments. Dressing percentage was lower for all pigs
fed DDGS.
Researchers from Kansas State University
(Linneen et al., 2007) evaluated the effects of DDGS
inclusion in three separate experiments. In the first experiment, 1,050 pigs (24 to 26 pigs per pen; 7
pens per treatment) were fed diets with either 0 or
15 percent DDGS to which 0, 3, or 6 percent fat was
added (6 diets total). Addition of DDGS to the diet did
not affect pig performance. However, addition of fat
improved average daily gain, and gain to feed ration,
regardless whether DDGS was included in the diet.
In experiment 2, 1,038 pigs (25 to 28 pigs per pen;
10 pens per treatment) were fed diets with 0, 10, 20,
or 30 percent DDGS. Diets containing more than 10
percent DDGS appeared to have lower daily gain and
feed intake , but there were no differences in gain to
feed ration . In exp. 3, 1,112 pigs (25 to 28 pigs per
pen; 9 pens per treatment) were fed diets containing
0, 5, 10, 15, and 20 percent DDGS. Pigs fed diets
without DDGS had greater daily gain compared to
those fed 20 percent DDGS. Feed intake tended to
be decreased with increasing levels of DDGS. The
authors concluded that 15 percent DDGS from that
particular source could be added to diets without
affecting growth rate.
Research from JBS United, Inc. (Gaines et
al., 2007) aimed to determine the effects of DDGS
inclusion with or without enzyme addition. Pigs (880
total; 12 pens per treatment) were fed a diet with either 0 or 30 percent DDGS or a diet with 30 percent DDGS or a diet with 30 percent DDGS with a supplemental
cellulose enzyme. No differences
were observed for daily gain or feed intake . However,
gain per unit of feed was lower for pigs fed 30 percent
DDGS, regardless of enzyme supplementation.
Carcass yield, loin depth, and carcass percent lean
were lower for pigs fed DDGS, irrespective of enzyme
supplementation. The authors concluded that when
feeding high levels of DDGS, a reduction in carcass
yield and lean should be considered in the economic
evaluation.
In a second study from JBS United, Inc. (Spencer
et al;., 2007), two experiments were conducted to
evaluate DDGS supplementation (DDGS contained
10.2 percent fat, 25.4 percent CP, and 0.86 percent
lysine) to nursery pigs. In experiment 1, 1,500 pigs
(20 to 27 pigs per pen; 15 pens per treatment) were
assigned to 4 treatments as follows : 1) control with 0
percent DDGS; 2) 7.5 percent DDGS in the phase I
diet and 15 percent throughout the remainder of the
6 week nursery period; 3) 15 percent DDGS starting
in phase 2 diets; and 4) 15 percent starting in phase
3 diets. The feeding program consisted of 4 dietary
phases. Pigs fed DDGS had greater gain to feed ratios, regardless of when DDGS was introduced to the diets .
No other differences were observed. In experiment
2, 300 pigs weighing 9.0 kg and 31 days of age (10
pigs per pen; 10 pens per treatment) were used to
determine the impact of DDGS feeding (30 percent)
with or without the addition of a combination of
enzymes (alpha-galactosidase, galactomannanase,
xylanase, beta-glucanase). Pigs fed diets containing
30 percent DDGS had greater gain to feed ratios than
pigs fed control diets. Supplementation of enzyme to the diet with DDGS improved daily gain compared
to the other two diets. The authors concluded that
DDGS can be supplemented to diets for nursery pigs
at 7.5 to 15 percent at any time during the nursery
period without negatively affecting pig growth
performance. In addition, the authors indicated that
the supplementation of enzymes to diets with DDGS
may further improve nursery pig performance.
- Eric van Heugten
Last modified January 29, 2008.
