Impact of sulfur on palatability and performance of pigs fed DDGS diets

Impact of sulfur on palatability and performance of pigs fed DDGS diets


Good afternoon. This is Hans H. Stein. I am
an associate professor in the Department of Animal Sciences at the University of Illinois.
I would like to talk to you today about the impact of sulfur on the palatability and growth
performance of pigs fed DDGS-containing diets. The outline I would like to follow includes
the following. First, I will give a little bit of a background for our experiments. Then
I will talk about the four experiments we conducted. Then I will show the results from
these four experiments, and finally I will talk a little bit about the implications from
this research. Corn grain contains approximately 0.1% sulfur.
Because the starch in corn is fermented during ethanol production, DDGS is expected to contain
about 0.3% sulfur, because most of the nutrients in DDGS is three times greater than the concentration
is in corn. However, the actual concentration of sulfur in DDGS is not always 0.3%. Sometimes,
we see values all the way up to 0.9% or even more than that. So, there is a lot more sulfur
in DDGS, in some cases at least, than what is coming directly from the corn grain. And
the reason for that is that sulfuric acid is sometimes used in the ethanol plants to
stabilize the pH during fermentation. And that’s why the sulfur concentration sometimes
is increased. Now, we know that sulfur can be a problem in cattle nutrition, and high
levels of sulfur can contribute to diseases in cattle. However, there is very little information
about the effects of sulfur in swine nutrition. It has been recognized and shown many times
that between 20 and 30% DDGS can be included in diets fed to swine without reducing growth
performance, but sometimes we do see a reduction in feed intake when DDGS is included in the
diets. And it has been concluded that pigs, if they have a choice, they will prefer to
eat diets that contain no DDGS rather than diets that contain DDGS. And we therefore
came up with the hypothesis that maybe the reduced feed intake that is sometimes observed
in diets containing DDGS could be related to the concentration of sulfur in DDGS. So the objective of this research was to measure
the effects of the inclusion of DDGS and elevated sulfur concentration levels on diet palatability
and pig growth performance. We conducted four experiments. The first experiment
was conducted with the objective to measure the effect of sulfur on feed palatability
using nursery pigs. And in the second experiment, we used the same diets to measure the effects
of sulfur in DDGS on growth performance in nursery pigs. The third and fourth experiments
were conducted with growing pigs. And in the third experiment, we measured the effects
of DDGS on feed palability or feed preference in growing pigs, and in the fourth experiment
we used those diets from Experiment 3 and measured the growth performance of growing-finishing
pigs fed diets containing different levels of sulfur in DDGS. The diets we used for the two nursery pig
experiments are shown here. We had three diets. The first diet was a control diet, simply
a corn/soybean meal diet containing 23% soybean meal, 73% corn, and then we had some other
ingredients — vitamins, minerals, and amino acids. The total sulfur concentration in this
diet was 0.22%. The we formulated a corn/soybean meal/DDGS diet and we had 20% DDGS in this
diet. The DDGS we used in this diet was selected to have a relatively low concentration of
sulfur, so the DDGS here contained 0.3% sulfur, and that is in the low end of what we usually
see in DDGS. And you’ll see the total concentration of sulfur in this diet was about the same
as it was in the control diet at 0.22%. However, we then formulated a third diet, and the third
diet was similar to the second diet with the exception that we added calcium sulfate to
this diet to increase the concentration of sulfur from 0.22% up to 0.34%. And the reason
we added this level of sulfur was that 0.34% would be the level of sulfur one would get
in the diet containing DDGS if the DDGS had the highest level of sulfur that we have observed,
which is around 0.9%. The diets for the growing pigs are shown on
this slide. As for the nursery pigs, we used three diets in this experiment. We had a control
diet containing corn and soybean meal mainly, and this diet contained 0.206% sulfur. We
again used a source of DDGS with a low level of sulfur to formulate our second diet, and
this diet contained 61% corn, 6% soybean meal, and 30% DDGS, and the total concentration
of sulfur in this diet was 0.198%. Then we had the third diet, which was a high-sulfur
diet. And this diet was formulated by adding 1.10% calcium sulfate to the DDGS-containing
diet. So the total concentration of sulfur in this diet was 0.375%. And as in the nursery
pig diets, this level of sulfur was calculated to be similar to the level of sulfur one would
obtain if we had used a DDGS source with 0.9% sulfur. The results of these experiments are shown
next. The feed preference of the nursery pigs is
shown in this slide. We have here, on the Y-axis, the feed preference on a percentage
basis, and on the X-axis, we have the different diets that were fed. The way we conducted
this experiment was that we had a total of 30 pens. In 10 of the pens, we had two feeders.
These two feeders contained the control diet and the DDGS diet, so there was a choice for
the pigs to eat either the control diet or the DDGS diet. The feeders were switched every
day, so that the pigs would not know beforehand which diet was in which feeder. So the disappearance
of feed from each feeder represents truly the preference of the pigs, and we measured
the disappearance every day for eight days. The second group compared the control diet
and the DDGS+sulfur diet. Again, we had ten pens, and we had two feeders in each pen,
and pigs were fed every day, feeders were switched every day, and feed disappearance
was monitored every day. And the third group had two feeders and in these feeders we had
either the DDGS-containing diet or the DDGS+sulfur diet. As is apparent here, when the control
diet and the DDGS diet were fed, we saw a much greater preference for the control diet
than for the DDGS diet; about 65% of all the feed that was consumed in those pens was the
control diet, and only 35% of the feed that was consumed was the DDGS diet. And looking
at the second group, we saw exactly the same picture; about 65% of the feed consumed was
the control diet, and a little over 30% of the feed consumed was the DDGS+sulfur diet.
So again, clearly the pigs preferred to eat diets containing no DDGS if they had a choice.
However, the third group showed that if the pigs have a choice between a DDGS diet and
a DDGS diet with high sulfur, there is very little difference in the consumption of feed,
and they pretty much eat 50% of each diet. There is no significant difference between
these two diets. So what this indicates is that pigs prefer to eat diets containing no
DDGS, but there does not seem to be any preference for eating diets with low sulfur versus diets
with high sulfur. So those were the results from the first experiments. We repeated this experiment with growing pigs.
And the setup was the same as for the previous slide: we had three groups of pigs, and we
had two feeders in each pen, and we had ten pen replicates per group. And again we saw
here that if the pigs were given a choice between the control diet and the DDGS diet,
they preferred to eat the control diet, so about 70% of the feed consumed was the control
diet, whereas only 30% was the DDGS diet. And we saw exactly the same picture if we
used the DDGS diet with high sulfur concentration; about 30% of the DDGS+sulfur diet was consumed
and almost 70% of the control diet was consumed. However, as was the case with the nursery
pigs, we also saw for the growing pigs that if the pigs had the choice between DDGS and
DDGS+sulfur diets, they seemed to eat about the same amount of each diet. So about 50%
of the DDGS diet was consumed, and about 50% of the DDGS+sulfur diet was consumed. So the
result of this experiment with growing pigs was exactly the same as what we saw with the
nursery pigs, where pigs prefer to eat the control diet if they have a choice, but they
don’t seem to really care whether there is a high or a low level of sulfur in the DDGS. Looking at growth performance for the nursery
pigs. The pigs were about 10 kg when we started, so they were approximately two weeks post-weaning,
and we fed them these diets for three weeks. So they were a little over 20 kg when we completed
the study. And we can see here that the average daily gain was significantly greater when
pigs were fed the control diet compared with pigs fed the DDGS diet or pigs fed the DDGS+sulfur
diet. However, there was no difference between the two DDGS-containing groups. They had similar
average daily gain. There were no significant differences in feed intake among the three
groups; however, the gain:feed ratio was greater for pigs fed the control diet compared with
pigs fed the two DDGS-containing diets. So that indicates that pigs utilize the feed
a little bit better if they are fed the control diet compared with the DDGS-containing diets. The growth performance for the growing-finishing
pigs was kind of similar to what we saw for the nursery pigs, where the pigs fed the control
diet had a greater average daily gain compared with pigs fed the DDGS and the DDGS+sulfur
diets; however, there was no difference between the two DDGS-containing diets. In this case,
feed intake was also greater for pigs fed the control diet compared with pigs fed the
two DDGS-containing diets, and the gain:feed ratio was greater for pigs fed the control
diet than pigs fed the DDGS and the DDGS+sulfur diets. So the results of the growing-finishing
experiment was very similar to the results from the nursery experiment. If we look at the conclusions from these experiments,
we saw no effect of the sulfur on feed preference for nursery pigs and we saw no effect of sulfur
on feed preference for the growing-finishing pigs. It appears that pigs prefer to eat corn/soybean
meal diets compared with diets containing DDGS, but if they have to eat DDGS-containing
diets, they don’t seem to care whether there is a high or a low concentration of sulfur
in that DDGS. On growth performance, we saw no effect of
sulfur on feed intake, which is also what we expected after seeing the lack of an effect
of sulfur on feed preferences. We saw no effect of sulfur on growth performance. However,
in this experiment, pigs fed diets containing no DDGS performed better than pigs fed diets
containing DDGS. And that was somewhat surprising because in previous experiments, we have shown
that there is no difference in growth performance between pigs fed control diets and DDGS-containing
diets. One reason for the reduced growth performance that we observed in these experiments may
be that the DDGS we used in these experiments is of a poorer quality than what we have used
in previous experiments. A few implications from this research … The implication is that the concentration
of sulfur in DDGS does not appear to affect feed palatability or feed preference of the
diets. The concentration of sulfur in DDGS also does not affect pig growth performance,
because pigs fed diets with low sulfur and high sulfur had exactly the same performance.
However, questions about why pigs fed DDGS-containing diets sometimes perform less effeciently than
pigs fed corn/soybean meal diets remain unanswered and more research in this area is required. With that, I want to thank you for your attention.
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