Slide 1
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.

Slide 2
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.

Slide 3
Some recent research measuring the tryptophan:lysine ratio. You can see 
that Wang 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.

Slide 4
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.

Slide 5
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.

Slide 6
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%.

Slide 7
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.

Slide 8
The results for Experiment 1: for average daily gain, using a breakpoint 
analysis, we found the result to be 20.1% tryptophan:lysine ratio.

Slide 9
For gain:feed, using a breakpoint analysis, we found the ratio to be 
19.5%.

Slide 10
And using plasma urea nitrogen, we found, using a breakpoint analysis, 
the tryptophan:lysine ratio to be 16.7%.

Slide 11
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.

Slide 12
Using a breakpoint analysis for average daily gain, we found the ratio 
to be 18.1%.

Slide 13
For gain:feed, we found the tryptophan:lysine ratio to be 17.4%.

Slide 14
And for plasma urea nitrogen, we found the breakpoint analysis to yield 
a result of 17.0% tryptophan:lysine ratio.

Slide 15
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.

Slide 16
If you'd like to learn more, please visit the URL on the screen. Thank 
you.