If you want all of the commercial data, more than you ever wanted to know...how to feed, what to feed, how much to feed, egg size, ...here is the link to the company holding the patent...
http://www.isapoultry.com/en/Products.aspx
I followed their protocol for raising my chicks as closely as possible and still follow their care instructions for the hens. I have had excellent results. They started laying at 16 weeks and all of them were laying by 20 weeks. We live in a winter cold climate and have very hot dry summers. The girls lay eggs very consistently no matter what the weather. And we do not have an insulated coop or any fancy chicken house upgrades. I do provide a bit of extra light in the winter. But that's it.
I have found that if you feed a high protein mix the eggs will get GINORMOUS but not containing double yolks. Since I don't want to encourage the formation of prolapse problems I keep their protein to no more than 22%, and then only when stressed. Otherwise I keep it around 18-20%.
I wanted only 15 last year but needed to order 25 for the minimum. By the time my chicken friends were done adding to my order we ended up receiving 100+ chicks. They shipped from Townline in MI all the way to northern NV. No losses and extras added. The people at Townline are incredibly friendly and helpful...I should know since I called to increase my order several times! Since we live out West none of the feed stores orders ISA's. This year I have added some Ideal sexlinks...(RIR x delaware) so we'll see how they compare.
You will see from the data on the website that the egg production drops off by 18 months of age. But I have found this true of almost every breed I've ever owned. In heritage breeds it was especially noticeable after the first molt and the first winter. So I started rotating my flock every year and this seems to work the best since we sell the eggs as a hobby and for a bit of extra gas money for the teenager who cares for the flock. It really doesn't cost us anything to do this as we pay for the chicks with the money that we make selling the hens. Of course we don't sell the hens until the chicks are laying. However, since the ISA's are very efficient and not as large as a dual purpose chicken (so they don't eat as much) and they start laying regular sized eggs at a young age...even the cost for feed to raise them to POL is covered by the sale of previous year's hens. We generally have around 20 hens per year at $8 each to sell = $160 which is more than enough to buy 20 more chicks and feed them to POL. There are quite a few people in my area that don't want to be bothered with raising chicks, aren't into the "production" numbers of eggs (just want a few fresh eggs for the family), and are happy to buy young hens.
My Townline birds are friendly, definitely keep the feed bill low (though I don't find them to be great foragers), and have done well with other breeds in our flock. I've only lost two, one to a coyote and one to prolapse. The prolapse one had a weird egg most of the time...but I've had that occasionally in birds from various sources over the years...it just happens sometimes. Otherwise they have been happy little birds.
Hopefully you can find someone to share an order with since I don't think you would be disappointed with your ISA's from Townline.
I'm not sure if it's because they eat a ton or just because they are big birds, but hey I'm not complaining much. hehehe The Leghorn ladies eggs size seems to increase with increased protein, but it doesn't affect the BCM girls as much.
