Scratch is basically like if a human ate mostly bread for their diet. Very high in carbs, low in protein, and low in nutrition. Each chicken should only eat, at most, 1-2 tablespoons of scratch grain a day. It only has about 8% protein. The minimum amount necessary for a laying flock, including the rooster, is 16%, but 17-18% is better. I would think it would take a long time for a poor diet to be deadly, but it certainly could weaken the immune system over them.What makes you believe the rooster died from too much scratch? Scratch is just the raw ingredients used in fortified feeds. Corn, oats milo and barley are perfectly safe for chickens. Wouldn't the hens of died as well?