I like wide body birds for several reasons. Wide males make better table birds, and are easier to get your hand inside the cavity during processing. Wide females can more easily pass eggs and are less prone to getting egg bound. They can also cover more eggs if you let them hatch eggs. The trade off is that the take more feed compared to thinner birds. When I say wide I mean wide skeletons not overweight birds. Overweight birds have lots of laying issues.
Wide bodies are likely in the Marans standard because the people who originally created the breed weren’t happy with the meat quality of the birds available to them and were intentionally breeding them for table traits. The way a chicken looks in the yard is directly related to the way it looks in the roasting pan.
