Effects of Dietary Standardized Ileal Digestible Isoleucine:Lysine Ratio on Nursery Pig Performance

Dr Mike Tokach, I congratulate the study team for the work done. Considering that although the inclusion of synthetic isoleucine in pig diets is currently unfeasible due to price and availability, determining its relationship with lysine is essential to enable the use of synthetic valine available on the market, with a compatible price. Even though I understand the relevance of the study, I would like to make some considerations: - It would not be interesting to include in the tables the values of essential amino acids versus non-essential amino acids. In this case, non-essential amino acids also important for piglets such as glutamine and aspartate should not be included. : - I have my convictions, that I am studying to establish the relationship of a certain amino acid with lysine, in the experimental diets the level of digestible lysine should be suboptimal. This would avoid the possibility of an excessive consumption of lysine, which could underestimate the ratio of the evaluated amino acid. As I am aware of Dr Tokach's experience and knowledge, I make my considerations in order to assess their consistency. With my thanks.

A few items that we consider in formulating diets for these experiments. We make sure we are below the lysine requirement by conducting lysine titration trials in the same facility with same pigs prior to doing the ratio studies. We formulate to a maximum SID Lys:CP ratio to provide enough nitrogen for synthesis of nonessential amino acids and add non-essential amino acids (glycine and glutamine) to increase nitrogen (CP) if needed. We also check that any other essential amino acid is provided at the higher end of requirement estimates relative to lysine to make sure the test amino acid is first limiting.

Royce Samford

I also agree with Dr. Tokach's considerations. But my point was that the use of glutamine as a source of nitrogen would be more efficient than glutamate, due to the metabolism of glutamine in the piglet's intestinal mucosa, in addition to producing the glutamate itself, it also provides the N of the amide group which is fundamental in the production of nucleotides that is used for cell multiplication in the intestinal mucosa. I also understand that the supply of glycine, not only by the supply of N but also has an action on the animal's immune system. It is an important source of N for the piglet. I would also like to clarify that my suggestion to include the relationship between essential AAs and non-essential AAs, would be to make it clear that this relationship is adequate. This is because sources of N can be included equaling the protein level, without this relationship being adequate. I made these clarifications to make it clear that I did not disagree with what was presented, I simply made some considerations that I thought were important.

Guoyao Wu
Thank you for the kindness of the information. I fully understand that the mixture of the two amino acids (GLUTAMINE + GLUTAMATE) is a matter of price, since glutamate can be produced in the intestinal mucosa from glutamine. There would be no need for its inclusion.