I recently started a poultry farm in Oklahoma, I went threw my first 130 Birds of Astrelopes,Sex links ,Rhode island reds, and Leghorns, With only a 2 bird loss, one i had to cull from the flock at 3 days old due to incubation problems, and one flux accident where a Bird layed his neck over a downed shovel handle and 50 mph wind blew a board over on it. I ordered 28 jersey Giants, 10 Sex links and 50 Cornish x rocks. I would walk into the cage and find one dead bird a day. I assumed the blood on them was due to cannabalism, I finally narrowed it down to a black lab who lived up the road. After a 15 bird loss, I got quickly back on track reinforcing the coop to avoid another dog situation. Being the bright one I am I allowed my australian shepards to herd my chicks with me at night. They are over achieve'r dogs always trying to do the best they can sometimes forgetting to do it with and for me. Again birds started dieing one a day dead in the cage like clock work. so i have ruled out dogs and other animlas now since i rebuilt coop, I walk outside and see a bird that looked as if it died in the air in my front yard, Quickly i panic and call the state testers who find no trace of bird flu or pull, each day brings a new death until the numbers reach 7 dead birds. I start reallly researching the what could be's ... as i go back outside to check i notice my dog in the chicken coop (the shepard, also keep in mind no birds were bitten or bloody they were just kinda dead like they slept and never woke up.) I walked in and my dog looked so confused as he was trying to herd the chickens into there cages like we do at night time, And at his feet was 4 dead birds who ran out of forward room so to speak. he herded them till they wouldnt move then herded some more. at least satisfied to know again cause of wierd deaths I chain up the aussie for good while chickens are out. few days pass and here we go again 1 bird a day dead in the cage or in the yard. I know cornish strands are a very hard strand exepecially in flat land Oklahoma where heats can be amazing some days and weather has a mind of its own. there on a sun diet 17-20% protien feed my own recipe corn milo oats Mixed at a local Co Op Wheeler brothers. first 2 weeks are a 28% feed also my own creation. I have a waterer inside and outside the Brooder coop. the tempratures have been 85-100 outside these days. I feed free range birds who go outside at sun up and inside at sunset. these birds are 7 and 4 weeks old they all seem so happy and cheerful and healthy then we wake up to a dead bird, I know it could be heart failure but there diet slows that down I also reduced the protein to assure slow growth (cornish do better this way imo). heres the strange part the 25 Rhode island reds in the brooder next to them are perfectly fine no deaths at all there can anyone perhaps help me with some advice I can provide what ever info you need thank you.