I would advise wheat rather than white bread. I don't think there's anything wrong with bread every day as long as they're not eating a ton of it. When I have stale bread, I'll tear up a slice among my five girls. As long as they're getting a balanced diet, eating their feed, bugs, grass, etc., a little bread every day shouldn't hurt anything.
I feed lots of bread because I have a connection for free old bread. They get what I get for free so may be white, wheat,a specialty or whatever. I feed 5 or 6 pieces two or three times a day when I go out to my free ranging hens. My welsummers, ameracaunas and etc chickens are all healthy and laying like crazy. There are probably 25 to 30 hens. my chicken math means don't count and you won't have to think about it!!
Some bread is a good deal more nutritious than other bread.
It would probably be safe to count it as a "treat" anyway. Some animal nutritionists say "not more than" 15% of their diet for any thing other than their rations.
I got an idea about what might be a reasonable amount of treats (scratch, scraps, garden veggies) by weighing the hens' feeder as it was filled each day. With your 5 chickens, you could say that they should eat about 1 1/2 pounds of their commercial feed, daily. Give them their treats, then see if they are "cleaning their plates" each day.
If they are getting so much bread that the 5 birds are only eating a little of their feed, you are probably overdoing the bread.
What I found was that I could give my hens far more treats during the winter time than I had been. During cold weather, they are really chowing down and it is just to get enuf calories to keep them warm. Of course, we are moving into the time of year when they may need cooling down rather than warming.
Perhaps, it is not so much a matter of making them sick, Foley. Many chickens can survive on not much of a diet.
I am trying to remember where I read a study on the diet of Jungle Fowl. The birds seemed to be living mostly on fruit.
There's probably not anything terribly wrong with a lot of fruit in a chicken's diet. But, a Jungle Fowl is only laying about 5 eggs in a clutch and maybe 2 clutches each year. So, that's about the best production you could expect from your laying hen if she had a "fruit-based" diet.
Bread quality varies. I bet you would have a very happy flock of Jungle Fowl if they could come across a loaf of bread every day