First, I believed the hype of soy and used it as a supplement for my goats, chickens and rabbits for 2 years. In that time, the goats exhibited various estrogen symptoms, like infertility, miscarriage and early labor and false labor. But also they exhibited poor growth, swollen joints and rickets like development for the offspring. I just coudn't understand why when I was buying the best of feeds- alfalfa and about a cup daily per head of soy. Then I read the Ploy of Soy in the Weston Price website, stopped the soy and the offspring were sold off for meat as they were ruined, the adults recovered, but the rabbits never recovered their fertility and died out and I had to start a new herd.
The chickens were much more tolerant of these things- birds are the only true grain eaters and thus have enzymes that split things that are toxic to mammals.
Here is a study that confirms soy is different in it's phytic acid absorbtion than the other high phytic acid grains. I found that feeding rice bran also high in phytic acid, gave me much better results than soy. However it has also been contaminated by arsenic USA wide. From manuring with arsenic contaminated chicken manure- they deliberately fed this to chickens in the subsidized chciken factory farms to deter parasites. So it is also in your table chicken meat. Though we got tremendous growth and health, we also had tumors from the arsenic, most of which have gone away now, since we stopped feeding. I nhaven't yet found a substitute that gives the calories, minerals and vitamins to replace it. Wheat germ gives great protein and calories, but it has virtually NO b vitamins,it is just high in E.