Thank you to those that have given condolences and well wishes. I am sure frustrated losing birds to weird and bizarre things. Necropsy explanations for this bird elude me.
I keep doing them and learning any way I can. So far in the last five months I've lost two birds to suspected lead poisoning (Grey Silkies, egg peritonitis (POL pullet), sudden death syndrome (Blue Slate turkey chick), and now a HRIR ten week old cockerel to balloon syndrome. (For lack of a better description). An interesting fact....I didn't hatch any of these birds from my own flock. They were bred and hatched on other farms. A very strong reason for me to close my flock and not bring another bird onto my place.
I did not consider trying to save this cockerel because I would never have bred him into my HRIR flock even if he survived. He was just coming onto eleven weeks old. I have over a dozen HRIR cockerels left to choose breeders from.
This birds cavity and around his organs and every inch of his body was so filled with air bubbles, there is no way using a needle to withdraw the air would have worked. He even had air bubbles around his heart and intestines in his cavity!
The only thing different about this bird that I noticed before today was how big he was and his comb and wattles were smaller than the other boys. Which made me hope he was a female. This bird didn't move around much. Just liked to eat...and eat...and eat.. He kept up with the rest of the flock when they moved around the yards and gardens. He kind of waddled like a duck. It wasn't until an hour before I culled him that he became like a balloon.
Warning! Graphic Necropsy Images ahead

He continued to fill with air. His skin became so stretched and taunt it was sad. Very sad. He made no noise breathing. He didn't move if he could help it. He didn't struggle.

When I picked him up he began to suffocate. He was a completely soft and filled with air. He is still a live body in this above image. I gave him a swift blow to the back of the head after taking this image and he died quickly. He could no longer breath.

Immediately after death he did not deflate. He is all blown up.

His feathers are sticking out because the skin is stretched so thin.

The following images are the numerous air bubbles within his body cavity and between his skin and body muscle. I've never seen anything like this. EVER.

His breast area was divided into two huge balloons of air. There was also lots of bubble air clusters around every organ.

One air bubble over his breast. I popped the other one when I spit his skin for the necropsy.

I examined his trachea the best to my ability and could find nothing out of the ordinary. I still believe there was something blocked or broken.
There are a lot of images. Rather than put them all here at one time, I'm going to group them.

The lungs were flat and his organs were becoming pale from lack of oxygen.
.
I keep doing them and learning any way I can. So far in the last five months I've lost two birds to suspected lead poisoning (Grey Silkies, egg peritonitis (POL pullet), sudden death syndrome (Blue Slate turkey chick), and now a HRIR ten week old cockerel to balloon syndrome. (For lack of a better description). An interesting fact....I didn't hatch any of these birds from my own flock. They were bred and hatched on other farms. A very strong reason for me to close my flock and not bring another bird onto my place.
I did not consider trying to save this cockerel because I would never have bred him into my HRIR flock even if he survived. He was just coming onto eleven weeks old. I have over a dozen HRIR cockerels left to choose breeders from.
This birds cavity and around his organs and every inch of his body was so filled with air bubbles, there is no way using a needle to withdraw the air would have worked. He even had air bubbles around his heart and intestines in his cavity!
The only thing different about this bird that I noticed before today was how big he was and his comb and wattles were smaller than the other boys. Which made me hope he was a female. This bird didn't move around much. Just liked to eat...and eat...and eat.. He kept up with the rest of the flock when they moved around the yards and gardens. He kind of waddled like a duck. It wasn't until an hour before I culled him that he became like a balloon.
Warning! Graphic Necropsy Images ahead
He continued to fill with air. His skin became so stretched and taunt it was sad. Very sad. He made no noise breathing. He didn't move if he could help it. He didn't struggle.
When I picked him up he began to suffocate. He was a completely soft and filled with air. He is still a live body in this above image. I gave him a swift blow to the back of the head after taking this image and he died quickly. He could no longer breath.
Immediately after death he did not deflate. He is all blown up.
His feathers are sticking out because the skin is stretched so thin.
The following images are the numerous air bubbles within his body cavity and between his skin and body muscle. I've never seen anything like this. EVER.
His breast area was divided into two huge balloons of air. There was also lots of bubble air clusters around every organ.
One air bubble over his breast. I popped the other one when I spit his skin for the necropsy.
I examined his trachea the best to my ability and could find nothing out of the ordinary. I still believe there was something blocked or broken.
There are a lot of images. Rather than put them all here at one time, I'm going to group them.
The lungs were flat and his organs were becoming pale from lack of oxygen.
.