Harmful to any bird not actively laying.
People say they feed all their birds layer because when a bird dies, they don't do a necropsy to find out the real cause. They say, "I don't know why he died".
The following study show that roosters die at nearly 4 times the rate of hens due to kidney damage.
http://www.pjbs.org/ijps/fin1947.pdf
It also affects sperm motility.
http://www.ncbi.nlm.nih.gov/pubmed/20434855
http://www.ncbi.nlm.nih.gov/pubmed/10780656
http://www.ncbi.nlm.nih.gov/pubmed/12530920
http://www.ncbi.nlm.nih.gov/pubmed/10780656
Last paragraph
http://www.poultryshowcentral.com/chicken_gout.html
Last paragraph
http://www.agbiosecurity.ca/healthy...m and Vitamin D3 problems in laying birds.pdf
http://ps.oxfordjournals.org/content/64/12/2300.abstract
Graphic photos of urolithiasis.
http://nhjy.hzau.edu.cn/kech/synkx/dong/2bao/UrolithiasisChina.pdf
http://naturalchickenkeeping.blogspot.com/2013/02/calcium-mixed-flocks-vs-mixed-feeds.html
I am often surprised when people do not know this. Just to stress the point, Stop the layer while the hens are molting even without a Rooster too. The extra protein in grower is good for them then.
How do you feed a roo a different diet than the hens if they are housed together? My roo gets layer feed because I can't think of a way to feed him separately.
I do both of these things. The flock gets visits in the evening and is fed grower in their pens.The only 2 ways I can think of are to house the rooster separately and give him conjugal visits for 3 days every 2 weeks.
Otherwise, feed a grower, finisher or flock raiser and make sure the hens always have oyster shell available.