Some of my girls still aren't laying and the ones who did stopped.

[KGreene]

Layer feed for 2+ months for non-layers is a potential problem.

Could you explain? Ive always been told (and read) that you could start layer feed at about 18 weeks. Is this incorrect? I haven't seen any issues within mine, in fact I just had one RSL begin laying two days ago and she's 30weeks and has been on Layena crumbles since I received her at 20 weeks (although I do have 2 others that haven't began laying yet... roughly the same age). They all also get a small amount of scratch each day too, as well as free ranging each afternoon and weekend. Will the Layena for so long prior to laying cause future issues?

 

[ChickenCanoe]

So if I switch back to grower, will they hopefully start laying?

There's no way to tell. My warning against excess calcium for non-layers didn't have anything to do with getting them to start again. Commencement of lay can be affected by many things, light, nutrition, stress reduction.

http://www.thepoultrysite.com/articles/450/several-reasons-why-your-hens-may-stop-laying-eggs

Could you explain? Ive always been told (and read) that you could start layer feed at about 18 weeks. Is this incorrect? I haven't seen any issues within mine, in fact I just had one RSL begin laying two days ago and she's 30weeks and has been on Layena crumbles since I received her at 20 weeks (although I do have 2 others that haven't began laying yet... roughly the same age). They all also get a small amount of scratch each day too, as well as free ranging each afternoon and weekend. Will the Layena for so long prior to laying cause future issues?

http://www.hyline.com/aspx/redbook/redbook.aspx?s=5&p=36
http://ps.oxfordjournals.org/content/64/12/2300.abstract
http://poultryinfo.co.za/articles/Old/avian-urolithiasis-eng.pdf
http://ps.oxfordjournals.org/content/67/12/1694.abstract
http://www.neobio.biz/database/n-5data5-2/n-5data5-2-7.pdf

Some of the layer feed labels do say to start at 18 weeks. The assumption is that all the birds are the same age and at POL. But, many small flocks are various ages and various breeds that consist of other than egg hybrids and commence lay at different ages.
All the research on nutrition and egg laying comes from the commercial industry so we need to look to that for guidelines in feeding more diverse flocks. Commercial flocks get less than 1% calcium till 16 weeks when they get a pre-lay diet of no more than 2.5% calcium. Then between 18 and 20 weeks they get the layer diet which jumps to 4%. They can do that because the birds are all exactly the same age, are raised on 8 hours of daily light and slowly photo stimulated during the pre lay period so that by 20 weeks of age, over 90% of the pullets are laying. Backyard and small holders don't do that and can't predict exactly when the birds will start to lay, especially after the summer solstice.

Unknown to most is that urolithiasis and resulting gout are one of the main causes of death in poultry. It isn't a single entity disease and is the result of kidney damage. Two of the primary contributors are Infectious Bronchitis and excessive dietary calcium as well as other things like water deprivation. When it causes death, it results from kidney damage much earlier in life.
People can't know if their birds have developed urolithialis without a necropsy. How many people do you know that have a bird die of unknown causes send the bird to a lab for examination?
All breeds and all lines are not affected the same way but I prefer to err on the side of caution.
Referring back to the commercial industry, their birds aren't pets. Their bottom line is maximum production for feed input. If they lose some to kidney disease, that's not such a bad thing since that bird probably wouldn't have been productive and no feed is wasted. People that name their chickens don't look at it that way.
Or put another way.
http://naturalchickenkeeping.blogspot.com/2013/02/calcium-mixed-flocks-vs-mixed-feeds.html

Another thing to consider on the same topic is longevity. Commercial layers rarely live over 2.5 years. Broiler breeders are replaced about every 30 months. Most backyard people don't do that and want their birds to live and be productive for many years. Commercial operations are less affected by renal failure. That said, broiler breeder males die at 4 times the rate of females, most likely due to excess calcium in the layer diet.

 

[KGreene]

???? ... So, if I am correct in my interpretation of that dissertation.... feeding pullets high calcium feed before they begin laying could potentially have adverse effects in regards to kidney function, although it may not effect egg laying what-so-ever.

The last two of my 30 week olds began laying today...They too have been on Layena since they were 20 weeks old. Should I expect renal failure from all my hens secondary to feeding them laying mash before they began laying?

 

[ChickenCanoe]

10 weeks is a bit long but provided 2 of the 6 kidney divisions are still functional, they can continue to lay eggs. The trouble is, there's no way to tell.
In some of the studies I cited, up to 40% of the birds were affected and as I said earlier, some breeds and some lines are more resistant.

Dietary acidification has been found to help in commercial flocks. That discovery was just in the last 10 years or so.
Adding ACV to water certainly can't hurt.