Hi Castle Farm,
I will certainly investigate the book you recommend,
Mixed corn is of course usually made up of wheat (around 80 to 90%) and Maize? So breaking it down:
Wheat:
I'd still say that it is a useful feed on its own if you have free range birds that can suppliment their protein intake with what they can forage to increase their protein (bugs, worms etc), or chickens that can have a lower egg production / slower growth.
Maize
Usually the most palletable in mixed corn and therefore birds will pick it out before the wheat but it is
very fattening.
It is used alot in Canada and other cold areas as birds are burning more fat in the sub zero temperatures to keep warm and I still recommend giving extra mixed corn in cold weather to birds.
Too much maize puts on too much fat in laying hens which is unhealthy for them. Feeding corn ad-lib will result in them taking a far greater proportion of maize than wheat and is how the hens get fat and reduce production. Most maize is imported to this country but for example farmers in France use it to fatten free range hens for the table.
Formulated Feeds
The research that has been done in more recent years has given us formulated rations that can meet hens requirements far better IMO - especially high production / hybrids.
The modern hybrid is small and has a huge output in terms of egg production compared to the farmyard hen fed only on grain in years gone by.
In my opinion, commercial feeds have been well researched and contain the right amount of protein and the correct balance of nutrients and minerals for chickens especially for good egg production, more protein is required than can be provided by corn alone.
Yes there are variations in the type of bird and their nutritional requirements as you rightly say but the same arguement could apply to feeding just corn, no feed can't match their nutritional requirements exactly all of the time but I'd like to think all birds have enough free range to suppliment their diet with insects, raw greens, worms and the like.
Certainly an interesting topic for debate
Mineral and vitamin suppliments are a different story, one for another evening
