I am looking to enter broilers in the fair.I need to know how to make them as big as possible but also reduce feed costs.
Hmmm this is a slippery slope with many opinions.
In my opinion, you need about 9-10 weeks, of feeding Roosters by the Welp hatchery guidelines, with up to 20% feed, I wouldn't go higher than that. But you also need to free range them and move their feed and water about so that they build up strong leg muscles and a good strong heart. Otherwise, you will have big dead chickens from leg problems and heart failure. Once they are past the free eating stage, I divide the daily guideline into three meals, so they don't have food sitting out all day. And I also ferment each meal for 24 hours (So I had one bucket for each of the 3 meals, and immediately after they received breakfast, I would refill with mash and water to get the ferment started for the next day.) Having water in their food helps Cornish X ALOT because they are very thirsty/dehydrated normally, and this gets more water into them, and makes their poos a lot better than the watery droppings they usually have. There is a big thread on fermented feed in the top of the Meat Birds page, but basically I just keep the food just covered in water, and you want it to smell sweet and yeasty like bread, not sour or spoiled. It needs a little access to air to help the process, but you can keep it partially covered to keep flies off, but keeping it covered in water helps keep flies away too, you may have to top off all the buckets while you are making each meal.
Reducing feed costs: search super hard to see if you can find a local mill where they grow, harvest, and process all of their own grains. We have one where each bag of feed is $10-$15 and it is non gmo. I wouldn't make your own feed because Cornish X especially are "race cars" as Joel Salatin would say, and they are growing so fast that everything needs to be perfect. Free ranging does offer them some ability to find additional food to eat, although around 6 weeks they will slow down on how much walking they do considerably. If you add more time to your grow out, you could get by feed them a little less each day and they will be better free ranging chickens. But over time you will end up putting about the same amount of food into them, just over a longer period. We spent $8 per chicken this year in just the chick price, shipping, electrolytes and feed.