We've been working with a small group of growers in the Southern Willamette Valley who are committed to raising chickens on pasture in small batches. We were experimenting with no-soy feeds this year and opted to provide protein with peas. We found that broilers don't like the green peas and kicked them out of their feeders. They didn't do this with the yellow peas, however.
Also, we found that the Cornish X variety out-gained the heritage breeds by a factor of 2:1 regardless of diet. This played a critical role in the profitability of the venture from the farming end, suggesting that heritage breeds may need to be priced differently next year. However, the heritage breeds we raised were happy and active, with a full growth of feathers during their tenure versus the Cornish X who appeared as absurdly fat with few feathers and little desire to forage or exhibit normal chicken behaviors.
Here are the numbers for the different sets of chickens grown this summer:
Note that the numbers in this spreadsheet were gained far from scientifically and any definitive answers on growth rates and responses to feed would need to be gained in a controlled experiment. We would welcome anybody to work with us on this next year, perhaps raising several varieties of chickens on two different types of feed in identical pastured conditions.