https://www.sciencedirect.com/science/article/abs/pii/S0377840116300293
“ 20 to 50 g/kg fat is usually added in commercial poultry diets depending on the relative prices of fat and cereal grains. The addition of fat above 40 g/kg is generally avoided in pelleted diets because of the negative...
15 protein is very low. Aim for 18% at the very least, 20% is even better. If your protein is only 15%, and fat is 5% (which should be fine), that means there's more calories there that come from carbs, than there would be in an optimal feed that's 20% protein. Excess carbs make chickens (and...