i_am2bz said:
Hmm, this is discouraging...:/
Well remember it is just one datapoint. (Well, two if you count the ISA Browns, but I strongly feel their problems are likely related to having been bought as ready-to-lay pullets in April which means they were hatched in Jan and 'pushed' with lighting. There is a certain sentiment in the chicken-production world that believes this contributes to 'female problems', which would be consistant with their fates)
There are certianly BYCers with sexlinks of various sorts who are still laying decently at 3 or 4, and probably some later.
"Sexlink" is such a catchall category, I would not get too attached to worrying about it, you will just have to see how YOURS perform.
How much cayenne do you add?
Enh, I'm not sure, I just kind of dumped as much over their scrambled eggs as it seemed like I could get on there without ending up with drifts of it leftover at the bottom of the bowl

A couple times over the course of a week or so. I have never tried this before but many BYCers swear it works so I thought I'd try it. It still *might* work, of course, just not on these particular chickens
What can be added for protein, if they won't eat cat food or eggs (tried those already)?
They don't eat scrambled eggs????? Wow, I can't help you then, even my chickens that won't eat any other people food will eat scrambled eggs (or even just broken into bowl, microwaved, then roughly ripped into pieces). Chopped up cooked freezerburned meat? Or, next time you boil or roast a chicken, give them the carcass to pick the last bits of meat off? Mine like that. (Some people feel funny about feeding chicken to chicken, on the theoretical basis that there might concievably be some prion disease in poultry that we don't know about, but me, I figure "<shrug>")
(e.t.a. -- sunflower seeds are also a decent source of protein [better than chicken feed anyhow], or cooked dried beans)
Good luck,
Pat