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Hello. My name is Dr. Grant Petersen, and today I'm going to talk to you about the estimation
of ideal standardized ileal digestible tryptophan:lysine ratio in 10-20 kg pigs.
First, a little bit on tryptophan. Typically, it can be anywhere from the third to fourth
limiting amino acid in typical corn/soybean meal diets, and typical diets can be supplemented
with either D- or L-tryptophan in swine; however, L-tryptophan is the only commercially available
form. You can also supplement tryptophan by use of intact protein such as soybean meal.
Some recent research measuring the tryptophan:lysine ratio. You can see that *** and Fuller in
1989 as well as Chung and Baker in 1992 yielded an estimate of 18% tryptophan:lysine ratio,
and Baker in 1997 was slightly lower with a 17% tryptophan:lysine ration. And the current
NRC has listed an 18% SID tryptophan:lysine ratio. More recently, Fent et al. in 2002
estimated the ratio to be 15.8%, Guzik et al. in 2005 estimated the ratio to be greater
than 19.5%, Susenbeth and Lucanus in 2005 estimated the ratio to lie between 17 and
18%, and Htoo et al. in 2010 estimated the ratio to be anywhere from 15.9 to 19.9%, and
Ma et al. in 2010 estimated the ratio to be 15% tryptophan:lysine.
You can see with some current pricing, diet formulation with different tryptophan:lysine
ratios can greatly influence the cost per ton of diets. In this case, going from a 17%
ratio to a 23% ratio had a difference of $9.50 per ton.
So, the overall objective of these two studies was to measure the SID tryptophan:lysine ratio
in 10-20 kg pigs using a holistic approach to obtain the values. We obtained specific
batches of ingredients for the determination of the ratio throughout the trial, and we
obtained specific amino acid requirements for 10-20 kg pigs at our Swine Research Center.
And we confirmed that the basal diet was deficient only in lysine and tryptophan.
For the trial setup, we ran two experiments. One using a corn/corn gluten meal/field pea
diet, and another using a corn/high protein distillers grains diet. The basal diets were
both limiting in both lysine and tryptophan, with lysine being 0.85% of the diet and tryptophan
being 0.1% of the diet, determined from previous trials. There were six treatments in both
these experiments. The treatments had tryptophan set at 0.10, 0.12, 0.14, 0.16, 0.18, and 0.20%
tryptophan, which had tryptophan:lysine ratios of 11.7, 14.1, 16.5, 18.8, 21.2, and 23.5%.
In Experiment 1, we utilized a corn/corn gluten meal/field pea diet with five pigs per pen
and nine replicates for a total of 270 pigs with an initial body weight of 10.32 kg. We
measured average daily gain, gain:feed, and plasma urea nitrogen.
The results for Experiment 1: for average daily gain, using a breakpoint analysis, we
found the result to be 20.1% tryptophan:lysine ratio.
For gain:feed, using a breakpoint analysis, we found the ratio to be 19.5%.
And using plasma urea nitrogen, we found, using a breakpoint analysis, the tryptophan:lysine
ratio to be 16.7%.
In Experiment 2, we utilized corn/high protein distillers grains diets, with four pigs per
pen, nine replicates, and 216 pigs total. The initial body weight was 10.05 kg, and
we measured average daily gain, gain:feed, and plasma urea nitrogen.
Using a breakpoint analysis for average daily gain, we found the ratio to be 18.1%.
For gain:feed, we found the tryptophan:lysine ratio to be 17.4%.
And for plasma urea nitrogen, we found the breakpoint analysis to yield a result of 17.0%
tryptophan:lysine ratio.
The conclusions from these experiments yielded a tryptophan:lysine ratio in 10-20 kg pigs
of 18.2%, which is an average of the breakpoint from both trials.
If you'd like to learn more, please visit the URL on the screen. Thank you.