As I clearly stated in the beginning of my previous post proteins are not all equal, you can't simply swap plant for animal protein and expect identical results, heck you can't even swap different animals proteins and expect the same results... The cold hard truth is a feed that says 16% protein is really should not be a treated as a quantitative measure of feed quality... A lower protein level feed that is high in the amino acids the animal needs is better than a high protein feed lacking those amino acids, the actual protein absorption rates and ability of the animal to digest said proteins far outweigh raw protein intake... And commercial feed companies are not ashamed to use even inferior animal proteins just to be able to advertise this or that percent on the label... All proteins are made from the same 20 amino acids, and the amounts of those 20 amino acids in any given protein source varies from the next source, even between different 'parts' of the animal used for the protein... So when said feed company switched to plant proteins as you claim they should not have used the same formula they were using when they used animal protein, the plant protein formula should have been supplemented with additional ammo acids to fill in the blanks that resulted when they switched proteins, most importantly for poultry (and other 'meat eaters') the lysine and methionine levels should have been supplemented significantly, and probably some additional plant oils and fats should have been added as well...
Evidence of absence is a fallacy, just because you have not seen one does not mean they don't exist and no one can create them... True, you likely won't find an elite commercial vegetarian feed as it's too much trouble to manufacture and the cost would be prohibitive for mass marketing, but that isn't to say one could not and has not formulated their own if they were inclined...
Sure there is a difference... The reason most people see and choose to use animal proteins in show birds is because it's the low cost, easy and simple path to achieve the results they desire, it's much, much, much harder and a lot more work to get the 'elite level' results using plant proteins, but that isn't to say it can't be done, it can... Most people just simply choose not to even try as there is a much, much simpler path to their goal using animal proteins...
One has to also realize that very few chicken owners are striving to achieve elite level results, just like most people that eat healthy and work out are not trying to compete in the Olympics... There is a point where a feed is 'sufficient' based on cost and your desired performance level... There are numerous examples of pro athletes and others that have excelled in their performance and health on vegetarian diets, this kinda debunks that it's a simple inferior/superior subject, and most certainly suggest that it's much more involved and detailed equation...
While it may be true the plant proteins on a 1:1 intake are inferior to animal proteins due to lower absorption rates and lower levels of necessary amino acids that omnivorous and carnivores bodies demand, if the pant based diet is adjusted to compensate for the lower absorption and lower specific amino acids (aka supplement, mix and match or eat more of this or that) found in plant proteins, plant proteins 'inferior' status can factually be negated... As I said above all protein, be it from an animal, plant, bacteria, fungi or what not is built using the same 20 amino acids, this is a fact the only difference is how they are assembled... Thus since they use identical building blocks, it's just a matter of getting the proper levels of those 20 amino acids absorbed into by the body, in the end it honestly makes no difference where they come from as long as the properly levels are available to be absorbed...
BTW, even though I might sound like a vegetarian, I'm not and I don't agree with vegetarian diets, but I spent a great deal of time studying nutrition at one point in my life and learned quite a bit, enough to know that many anecdotal claims about proteins don't hold up to scientific fact and study, that is once when you dig in deep and look at the deeper picture not just the surface...
