Very interesting, clear and didactic. Excelent bibliography review. Congratulations

Congratulations on the article, considering the importance of the revised article. I take this to reaffirm some points that I mentioned earlier. Based on the information contained in this review, it can be perfectly deduced that, in practice, the reduction in feed crude protein, which is based on the ratio of essential amino acids to lysine, is the ideal protein for the animal category in question, can be questioned.
This is because the information that underlies these ideal protein proposals is usually obtained under conditions of lower immune challenge than the field environment. Thus, amino acid ratios in the ideal protein need to be readjusted according to the farm's degree of challenge. Another aspect, not least, is the fact that some nonessential amino acids, such as glutamine, glutamate and glycine, among others, become semi-essential in conditions of increased immune challenge. Thus, the reduction of the protein level by decreasing the concentrations of these amino acids in the diet may compromise the development of birds.

A comprehensive study and an excellent research investigation.

Excellent study and research, but deficient in standard Amino acids ratios and levels for best immune response.

In my opinion, one of the most important role of amino acids, especially Arginine and Methionine (L,DL) is helping the immune system in broilers. As you know, methionine is one substrate for Glutathione synthesis. Cys, GABA, Glu and Gln and some other amino acids are very important in this topic.

Dear Dr. Rose, in my opinion, the nutritional requirements reported by genetic companies are for healthy and stress-free animals and the ideal protein profile may vary in the order of limiting amino acids, for example, an animal challenged with enteritis may have a higher threonine requirement. For the main component of the intestinal mucosa and a viral disease can increase the needs of arginine, glutamine and others. The nutritional requirements of an animal depend on its sanitary conditions (healthy or sick) and stress.

How much increase in the requirement of amino acids to immune system in diets?

Amin, as an example, when I do a consulting to a poultry or swine company, before designing the diets by productive stages, I evaluate the challenge that it has: viral, bacterial, fungal (mycotoxin) or parasitic (coccidia, tapeworm or worm), then evaluate the low, medium or high challenge level, then increase the nutritional requirements recommended by the genetic house in a range of 0 to 5% or greater.

Interesting article. This article inspired to be applied in antibiotic-free feed.

Juarez Donzele Hi Prof. Donzele, thanks again for your comments. They are relevant and interesting, as always. I agree that the ideal protein ratio is dynamic. Understanding amino acid requirements in these conditions will allow us to utilize low crude protein diets, while being assured that supplementation of the essential amino acids is not limiting. For this reason, I also see a high value in conducting nutrient requirement research in non-optimal environments (i.e. environmental stressors, pathogen challenges etc.)