Hello everyone, my name is Andrea Mallea. I am a master student in the monogastric nutrition laboratory of Dr. Hans Stein at the University of Illinois and today I will share with you the results of one my experiments about the inclusion of corn protein in diets for weanling pigs. This presentation took place at the 38 Spanish feed industry FEDNA congress, on December 13 of 2023. 

Corn protein is a co-product from the dry milling ethanol industry. However, only the starch and other fermentable carbohydrate fraction of corn is converted to ethanol, and therefore, the remaining protein, oil, fiber, and ash can be concentrated in co-products. The most used corn co-product are the distillers dried grains with solubles (or DDGS). However, with the use of new technologies, a post-distillation separation of protein from the whole stillage, utilizing only mechanical separation can be made, obtaining a new co-product with approximately 50% of crude protein. This new co-product is called corn protein. 

The high level of crude protein in corn protein made this ingredient a good option to be included in diets for swine. However, when nutritionist formulated diets for pigs with corn protein, there was a reduction in growth performance of those pigs. A reduced final body weight, average daily gain and average daily feed intake were observed. 

For that reason, the researchers looked at the amino acids composition of corn protein compared to other protein sources, as soybean meal. In this slide we have in the x-axes SBM on the left side of the screen and corn protein on the right, and in the y-axes the concentration in percentage. We can see that the concentration of Lys in soybean meal is higher than in corn protein. Tryptophan follows the same tendency. However, there is more valine in corn protein than in SBM. The concentration of Ile is similar in both ingredients. But, the Leu concentration in corn protein is almost as twice as in SBM. Therefore, it was concluded that using corn protein may lead to an oversupply of Leu in the diets. 

Leucine is an essential amino acid for pigs, and along with Val and Ile are the family of branched-chain amino acids. They are called branched-chain amino acids because they have a branch in their side chain. Because of this similarity in their structure, they share the first 2 steps in their catabolism. We have the BCAA being absorbed in the small intestine and transported to the liver via hepatic portal vein. Then all the excess of amino acids that were not used for protein synthesis will be transported to the skeletal muscle, where they will be deaminated by the same enzyme, BCAT, and the result will be these 3 keto acids, KIV, KMV and KIC depending on which AA they came from and then those branched-chain keto acid will go back to the liver and another unique enzyme will convert those keto acids in metabolites than can the further metabolize. The key point is that we have 2 enzymes that work on all those 3 amino acids. Therefore, having too much Leu will cause having to much KIC and that will overstimulate the dehydrogenase and the transaminase and end up degrading more Val and Ile. 

Now let’s see which is the relationship between Trp and BCAA. Tryptophan is transported into the brain from the bloodstream via LAT1 transporter. In the brain, Trp is the principal precursor for synthesis of serotonin and serotonin plays a key role in regulation of feed intake. However, Leu uses the same transport as Trp, meaning that when there is too much Leu, they will compete for the same transporter. As a result, there will be less Trp in the brain, and therefore, less synthesis of serotonin and a reduction in the feed intake. 

Therefore, the hypothesis of this experiment was that corn protein can be included in diets for weanling pigs if these diets are supplemented with extra Val, Ile and Trp, without having any negative effect on the growth performance or blood characteristics of pigs. 

Ten experimental diets were formulated. There was a control diet based on corn and SBM, and two basal diets. The basal diet 1 had a 10% of corn protein and basal diet 2 had 20%. As we added more corn protein, the SBM was reduced. All the other diets were based on the basal diet 2, with the addition of crystalline amino acids, either Val, Ile or Trp, individually in pairs or all the 3 AA in the same diet. All the other AA meet the requirements according to the NRC of 2012. 

A total of 230 weanling pigs with an initial body weight of 6.24 were used. There were 8 replicates per treatment divided into 2 blocks. There were 2 phases, phase 1 was from d 1 to d 14 and phase 2 was from d 15 to d 28. At the end of each phase, the pigs and feeder with the leftovers were weighed and recorded. Two blood samples were taken from one pig per pen on d14 and d 28 and fecal scores were visually assessed every other day. 

With the data obtained the Average daily gain, average daily feed intake, and gain to feed ratio was calculated. The plasma obtained from the blood samples was analyzed for Blood urea nitrogen and albumin. The statistical analysis used was the proc mixed of SAS, with the pen as experimental unit, the diet as fixed effect and the block and replicate within block as random effect. 

Moving on to the results, I will set up my slide first, in the x-ases we have the 10 different diets, starting with the control diet on the left, then the basal diets and the other treatments with the different amino acids supplementation, and on the y-axes we have the parameter evaluated. The asterisks on top of the bars means that they are significantly different from the control. The final body weight on d 28 was affected by the inclusion of corn protein, as we added more of the ingredient, the body weight was reduced as expected but the only diet that was not significantly reduced was the diet with the supplementation of all 3 AA indicating that we can overcome the negative effects of excess Leu in the diets by adding extra Val, Ile and Trp. 

Regarding the feed intake, an excess of Leu will reduce the synthesis of serotonin and therefore, reduce the feed intake. We can see here that the reduction of feed intake as the corn protein increased in the diets was as expected. However, adding only Trp may not be enough to overcome the negative effects of excess Leu. Therefore, the supplementation of these 3 AA is necessary to increase the daily feed intake in weanling pigs. 

There was no significant difference regarding gain to feed ratio, there was a little bit of variability but not difference.

There was a significant reduction in fecal score as corn protein was included in the diet when compared to the control diet. A lower number is better because it means that the feces were most likely to be normal. 

The blood urea nitrogen is an indicator of efficiency in protein synthesis. A lower value will be better because it will mean that the diet had a better amino acid balance and therefore, there was a lower deamination. The lowest Blood urea nitrogen was when we added the 3 AA, meaning that this diet had the best balance of AA for protein synthesis.

Albumin is a protein that transport the nutrient in the blood, it means the pigs fed the diets that were significantly different to the control diet were not as efficient in nutrient transportation as the pigs fed the control diet or the diet the 3 amino acids supplementation. 

In conclusion, corn protein may be included in diets for weanling pigs if these diets are fortified with extra Val, Ile and Trp without having a negative effect on the growth performance or blood characteristics of pigs. 

With that, I would like to thank to the Hans Stein monogastric nutrition laboratory for their support during the experiment. And Thanks to you for listening. If you have any questions, please feel free to reach out via email at amallea@illinois.edu or visit our website at nutrition.ansci.illinois.edu.