All my chickens died overnight for no apparent reason

[Northern Flights]

I won't argue anything too strenuously and do not seek to turn this into an episode of CSI. If my comments raised any hackles I offer sincere apologies, it was not my intent. My only hope is the OP can find a resolution that prevents further losses.

 

[jaxonann]

I'm sorry for your losses. If mama hen hasn't been getting off the nest much she may not have ingested as much toxin if that's the case or have been up and moving to be exposed to other agents.

 

[geezlouise]

I had read that you need adequate ventilation in you coop at the top as the poop makes a gas that will build up and hurt the chickens. You might check this as to keep them safe we tend to close up tight! Have all kind of creatures around my chicken coop but fencing has kept them out. Sorry about your loss.

 

[jane s chickens]

Ammonia if your coop is not ventilated

 

[cheeseheadken]

Thanks for your suggestions. I've had chickens in this coop for 5 years and it's pretty well ventilated. The chicks are about 8-9 weeks old (not sure - they showed up one day a few months back!). They were in the same coop and have access to same food and water, which leads me to think either gas or the other chickens got into something the mama kept her chicks away from. Wondering if perhaps there is another animal's carcass on the property that is decomposing. Botulism?

 

[cheeseheadken]

Anyway - thanks for your thoughts. I just wanted to check to see if there was anything I was missing (and there was - I hadn't thought of gas!) I'll swap out feed and water and check to make sure the coop is adequately ventilated. Thanks again!

 

[HenOnAJuneBug]

Gas poisoning is very unlikely. CO2 is non-toxic and only kills when it's concentration is so high that it excludes oxygen. That's not going to happen in a coop unless you have a bucket of dry ice there. Sounds like maybe something they ate.

 

[DuckDuckGooseMum]

I'm so sorry for your loss! I understand how devastating something like this can be. It does sound like poisoning. I would certainly consider the neighbor possibility. We have a dreadful neighbor who poisoned our beloved German Shepherd and her puppies. It's unbelievable that people could be so cruel, but they can indeed!
It sounds like you have been given some great advice & information to help you try to get to the bottom of things! At the time I know you are sad & bewildered but it's also the most critical time to take action to ensure this does not recur.
Have you had any conflicts with your neighbors? Has someone complained about your chickens or have they wandered into anyone else's yard? It may be well worth the small cost to have your feed checked out and possibly get an autopsy on one of the birds. If someone did do this, they should be punished for it. It's a terrible thing, but it would be even worse if it happened again.
Until you know what happened, please do not use the same feed for your remaining hen & chicks. I wouldn't store it anywhere that anybody else can gain access to. I'd take a good sized sample of the water and the food and then dispose of it all carefully. It wouldn't hurt to check all ventilation sections and doors for any evidence of tampering and take a good walk around the pen. You may find a footprint or cigarette butt, etc that could help figure out if this was indeed a deliberate, malicious act.
If there's other neighbors with poultry, you might check with them to see if they have experienced any problems or losses. I'd go further to suggest adding a concealed game camera placed high enough to prevent the birds from setting it off.
Sincerest condolences and please update us with your findings!
God Bless!

 

[SunHwaKwon]

Have you had any heavy rain lately? That causes me issues where I am at - when we first moved here it seemed I would lose 2-3 birds after a heavy rain and my thought was that it causes a spike in mold or mildew or some respiratory issue. Luckily it hasn't happened recently. Rain is infrequent here but it is very humid and when it pours something happens that doesn't mix well with the chooks. I can't even do fermented feed anymore whereas that was what I primarily fed before we moved down here.

 

[Northern Flights]

I would lose 2-3 birds after a heavy rain and my thought was that it causes a spike in mold or mildew or some respiratory issue...

Fungus is indeed a malevolent and ever lurking predator that most overlook and factors high in my suspicions as to cause -- either through feed as well as environmental. Even though things around here only rarely get somewhat summer-like we still get a great deal of fungus and I'm maniacal about controlling it, even on my lawn. I can only imagine how much worse it must be in warmer climes.

Most fungus is utterly benign, but some... well, it's just plain nasty. I am convinced it is not of this world, but I will work hours for a plate of pan-fried mushrooms. Yum.