I seem to have gotten the meat hybrids through the cocci bout. All but one are still going well and appearing completely healthy.
The one I lost was obviously very sick and unable to stand or walk. He was culled and given an amateur post mortem. The ceca (two long 'horns' coming off the main gut) were both full of dark blood. Clearly he had severe cecal coccidiosis. However there was an unexpected post mortem finding, and that was a large grey tumour or growth under his breast. It was the size of a broad bean, which is large for a chick not quite 5 weeks old, and quite hard, with a covering of many blood vessels. I don't know what to make of it beyond presuming it was a type of cancer, but hopefully there won't be sequels.
For the other birds, treatment was mainly a coccidiocide (sulphaquin — which is no longer able to be purchased) but I also moved the pen every 24 hours to new ground, and gave them all 2 days on pure chick starter (medicated), then slowly changed the diet back to 50/50 commercial/home mix. Now I'm moving the tractor every 2 days. I'll gradually extend the length of time between moves.
I've also taken the layer type chicks out of that pen and put them with the ancona chicks, while taking the malay x 'mother' back into the layer flock. The mother had to go back to the flock because she would have killed the layer type chicks that had been raised among the meat hybrids (remember she rejected them earlier). However 5 week old chicks are quite good at accepting others of their own age and size. Meanwhile raising all the baby layers together is better in terms of keeping an eye on their diet and health. If I'd left them with the meat hybrids they would probably have been starved out as the meat birds grew (and layers at 5 weeks on do like to roost, whereas the meat birds shouldn't).
All the chicks are on 50% commercial (medicated) chick grower and 50% home mix. The medicated grower component will be reduced in the next 2 weeks. By week 10 I mean to have them on an entirely natural diet (though not organic due to price and sourcing issues). By 'natural' I mean fresh natural greens, occasional bugs, grains and legumes, oilseeds, probiotic soured milk, fresh or mealed meat, yeast and shell grit. This contrasts to commercial feeds which have petrochemical-derived methionine to make up for the amino acid shortage in the wheat-soy base.
I've become aware that I may not have enough methionine in their diet, so I've started to increase soured milk. Signs of lack of methionine were that the meat hybrids (just like the sussex) have been feathering a little more slowly than I expected, especially around the rear end. The sussex did feather up eventually, but I do feel a bird should be fully feathered at 6 weeks.
I'm also trying fresh pet mince, but this time I'm soaking/cooking it first, to extract some of the preservatives that destroy thiamine. Ironically cooking also destroys thiamine, but this only affects the meat. I take it that if you feed sulphur dioxide laced meat it also destroys thiamine in the other feeds given at the same time.
By week 12 I'll roughly sort the keepers from the freezers. Keepers will be well grown but active. If all the birds still appear happy then I won't process any. Why hurry? If they're doing well, haven't overgrown their legs and basically seem to be enjoying life, then I'll be happy too. If they look happy but a bit crowded, I'll move some to another pen. No drama. By the time they start to crow, however, I won't have much choice — I have neighbours to think about, and only one sound-deadening rooster shed (which I've divided in half down the middle so I can keep a mature rooster with hens on one side, and young growing cockerels together in the other — each shed side has an exit to its own pen).
Eventually with the meat birds I plan to get down to a manageable bunch of healthy-as-possible girls, which will stay in the tractor. When they begin to lay, I'll start putting a rooster in with them during the day, and collecting and setting eggs. A majority of the offspring should be a lot longer lived and healthier than the meat parents, and should be genuinely good dual purpose birds.
After I get to the stage of having healthy heavyweight dual purpose birds that don't go broody too often, and also lay quite well without reproductive problems, I'll look at crossing them to some of the purebred utility dual purpose breeds. I should be able to introduce some fancy colours and other traits (for instance cochin or brahma would help with temperament). But that's for the future, if I make it that far.
This is all trial and error — as you can see, I've made errors in the past (e.g. cocci). The methionine question is still up for grabs. But so far I don't think any major damage was done. Even if my birds stay slightly slower to feather than normal, as long as they're growing well methionine may not be a dramatic issue. In any case I don't want birds that put on meat as fast as the hybrids — such fast growth is a product of industrial farming, and can't really be sustained without it.