The meat birds are Ross Cobbs, a breed specifically reared to grow quickly.
If they were intensively reared, they would be fed growth promoters, kept in a shed so they can't move around and will be slaughtered at 6 weeks old. They grow so quickly that their legs are unable to hold their weight, and for the last week of their lives, they often cannot walk around.
We keep ours outside where they eat lots of grass as well as grain, chicken food and other vegetable and fruit scraps. They grow slower and their legs grow strong. We slaughter at 11 to 13 weeks old, then hang in a fridge for 2 weeks. This intensifies the flavour so the meat really does taste like chicken!