I am new to BYC but this is a great forum! I have raised Rock Cornish X for several years now but am experiencing a higher than normal mortality rate (>25% so far). The birds came from Mt. Healthy as I had good luck with them last year. At around 4 weeks, some of the birds just started falling over dead (now at 5-1/2 wks). There are several that were smaller and may be hens (they were all supposed to be cockerels). It is only the small birds that are doing this. After speaking with Mt. Healthy, they do not know for sure but suspect heart attacks. If so, it seems like the larger birds would be the ones expiring. I have fed them per Mt. Healthy's recommendation of 23% protein for the 1st three weeks and 20% afterwards. Is this just a bad batch of birds or something else? Any help would be appreciated.