If my Cornish X are free ranging....

It depends on your goals.

There is a local family that uses broilers to clear areas of rough vegetation. They do not offer any supplemental feed, as they want the birds to ravenously devour all plant and animal life in the electronetted area. They accept the consequence that weight gain will be MUCH slower, they have to butcher later and the CornX Carcasses will look a bit more like a heritage/rubber chicken carcass than the nice rounded CornX you see in a store. Their feed costs are much lower, and they have fewer leg problems, but they note the meat can be tougher.

We have offered free choice feed to CornX on pasture and they spent far too much time camped around the feeder and not foraging. So we needed to regulate when they had feed and when they did not to encourage some exercise and vegetation consumption. We take feed away over-night (they are asleep any way) and then they charge the pasture in the morning when let out (6am). By 7:30 am when we put out the feed, they've had some healthy activity and eats and can plop down in front of the feed trough for the rest of the day if they want to. We got a nice carcass.

You will need to experiment a bit to find what produces the results you like.

As for feeding milk, it is animal protein but is not on the natural diet of birds. I imagine they can digest it just fine in small amounts. Do you have less expensive forms of animal protein available for them? Worms, crickets, moths, beetles, human meal leftovers, fish cleaning left-overs, etc.

 

I have feed for my meat birds 24/7, however, at night it is dark so they don't eat b/c there is no light, and they free roam 3+ weeks on. I usually don't have leg issues, but as previous poster states you'll need to find out what works for you.

 

We did things differently this year. I usually give them food during the day to eat while free ranging and pull it at night. When I would feed them in the a.m., they'd gobble it up like they're starving and look like they would like to eat me and each other in the process. I ran into problems with this because my other birds that free range would be eating the meaties feed all day instead of free-ranging and I don't like this mainly because I like to finish mine the last few weeks on whole grains and organic feed and I can't afford to let the layers and roos eat it all.
So, this year, for the last few weeks, I filled the feeder up in the evening when I put them in the pen (they gladly go in there for the food then I close them up) and it's enough to last them the rest of the daylight hours, then there is enough left for them to eat in the morning before I let them out. I throw whole grains out for scratch during the day so they're not so ravenous at night. Basically they had food available from 6pm to 8am (approx) the next morning and then the grains during the day. This has worked out really well and I will get them back from the butcher today so we'll see how they did. I didn't want them too terribly large so we butchered at 6 weeks.
This will be my plan from now on - day olds free choice for about a week and a half, then pulling feed at night until they move to the outdoor pen - about 3 weeks, when I'll switch and feed evening through morning with free range and scratch grains during the day.
We did slow broilers last year and they did free range very well but I think they ate so much feed and it felt like they were here forever! I think we'll do the cornish x from here on out. I've only done them twice and in small batches but we've had good luck so far.
Kim