Hi Jackie!
That's a great question.
Its TRUE that birds NOT in lay (juveniles, roosters, broody's, molter's) should NOT be fed "LAYER". or calcium in excess of 3% long term as it *COULD* (doesn't mean will) cause issues including gout, kidney failure, and even sudden death.
Some folks will feed only layer ever including roosters and may never have an issue. Others will never have their birds necropsied and will presume a death was a heart attack. Some have had issues but caught it and made corrections according to their new understanding.
For ME.. I have BANK invested in my flock.. not many $3 birds around here.. aside from the time spent already to get where I am I in my chicken breeding adventure... Feeding something knowingly that *could* cause issues for one of my valued roosters would be doing myself and my flock a huge disservice. So even though "Flock Raiser" cost more than "layer".. oyster shell is cheaper than protein, which a 3% more of the fill in layer feed comparatively. But also, "layer" has less amino acids and protein in addition to the extra calcium. This makes them MINIMUM feed required to sustain light bodied layers like Leghorn in laying condition. I'm not aiming for minimums in my household.
To ME.. after genetics, everything immune system related starts with diet and nutrition. Since making the switch to Flock Raiser away from layer... my older birds now have MUCH less harsh molts and return to lay sooner. They become less withdrawn than previous molts.
Since it has more nutrients.. I also don't need to worry about they are getting free range (most grass is low protein and bugs are high fat) and gives a little leeway if I want to offer lower nutrient snacks on occasion. (I don't do corn or scratch, bit many do)
Now, I am an AVID hatcher... and 22% protein was shown in studies to give the highest hatch rate... which to me says more nutrients inside the eggs my family is consuming.. And I keep chickens BECAUSE I want want my birds and eggs to be better than those of "Big Chicken", not equal to.
That being said, the whole kidney thing is PARTLY genetic.. some folks have fed ONLY (organic) layer feed and had roosters live past 9 years old. It isn't MY personal choice.
But with NO fear mongering.. this is the information as I see it. Please decide what you are comfortable with.. for YOUR flock!
I now never switch, which is good for me as I have a constant barrage of chicks, broody's, molter's, layers.. what have you.
Please note.. by law in the US, each feed is labeled with the appropriate age and species it's formulated for. Layer feed is formulated for layers.
Terms.. grower, layer, all flock, flock raiser, meat bird, breeder, starter, etc... all are confusing terms made up by different companies. The MAIN difference is always going to be protein and calcium content followed by amino acids and the differences diminish after that;. I buy the one I like the ingredients of the most with good amino acid content. I have spent hours upon hours at my local feed stores reading and comparing labels.
Best wishes whatever you decide!
ETA: fed to juveniles, excess calcium content can even stunt growth and delay onset of laying.
