Hen missing butt/vent

[Jubaly]

Yesterday my husband went to go feed the chicken and noticed a large amount of blood all over the coop. It was still closed from the night. So he gives the chickens a once over and found one of our hens with an open cavity in her back end. You could literally see right through her missing butt, vent and intestines. There was a very bloody egg and 3 of our chickens heads had blood all over them. We have a red heat light in the coop so they won't eat each other. I have not a clue as to what happened, she passed shortly after we found her.

 

[coach723]

It sounds like she may have prolapsed during the laying of that egg and then was cannibalized by the others. As upsetting as that is, it's fairly "normal" behavior. They are attracted to red, so when there is blood present or red tissue, they are very likely to peck at it. That is unfortunately a risk when a bird prolapses and it's not noticed right away. They will sometimes cannibalize a bird that has died also. As severe as the injury sounds, there is likely nothing you could have done to save her.
Where are you located, generally? If these are adult birds, fully feathered and healthy, it's unlikely that you really need to provide the heat lamp at all in the coop.
How much space do they have, for how many birds? Sometimes things like this are more likely when birds are too crowded, but it can happen in even the best set ups.

 

[Jubaly]

It sounds like she may have prolapsed during the laying of that egg and then was cannibalized by the others. As upsetting as that is, it's fairly "normal" behavior. They are attracted to red, so when there is blood present or red tissue, they are very likely to peck at it. That is unfortunately a risk when a bird prolapses and it's not noticed right away. They will sometimes cannibalize a bird that has died also. As severe as the injury sounds, there is likely nothing you could have done to save her.
Where are you located, generally? If these are adult birds, fully feathered and healthy, it's unlikely that you really need to provide the heat lamp at all in the coop.
How much space do they have, for how many birds? Sometimes things like this are more likely when birds are too crowded, but it can happen in even the best set ups.

I live in western Ontario it's already snowing, it reaches -40 here definitely need the heat light. last year I didn't have one and lost some wattles and such. It's a back yard flock. I have 15 birds now in a 4*6*6 coop with a second floor and an attached 60sqf run.

 

[coach723]

You might do some research on coop ventilation, often times frostbite is more a function of too much moisture in the coop from their respirations over night, which settles on combs and wattles. Just their breathing in and out can cause a LOT of moisture. Feel your coop walls and ceiling early in the morning on a cold morning to see if they feel damp or wet. Even far northern climates have traditionally used open air coops with success, as long as the birds are dry and can get out of prevailing winds, they usually do fine, if they are healthy. There is a very good (and old, written in 1924) book called Fresh-Air Poultry Houses, By Prince T. Woods, M.D., Norton Creek Press, that covers the subject really well. I'm not trying to argue, honestly, but many, many times frostbite is a result of a too closed coop, rather than the opposite.
Beyond that, the minimum recommended space for chickens is 3 - 5 square feet per bird in the coop, 12 inches of roost space each, if they have access to outdoors. If they are kept inside for periods (like inclement weather) then they need much more. Outside run space minimum recommendations are 10 square feet per bird. These are minimums and the actual space is very dependent on the birds themselves. Dominant and agressive birds may demand/need more. The truth is, the more space you can give them, the better. There are rarely issues with "too much" space, there are often issues with too little. If you are able to give them more room in the outside run, that may help, probably the easiest adjustment for now.