Dead Stock

An old farmer once told us that "where there is livestock, there will be dead stock".  We've had our share of casualties here.  Any farm will.  Last year we had a weasel get in and claim three hens.  We had some mean old roosters kill one hen named "Julie" and two were lost to dogs.  We had our bottle lamb "Baby" die two days after we got her.  We're pretty sure Sugar the sheep got too rough playing with Baby.  Right now we've got chicken issues.  I had a rooster with frozen feet here about a week ago and brought him inside, but I noticed gang green in his one foot so I put him down yesterday.  Last week I went out to the chicken coop to find a hen dead.  It was hard to tell the cause of death because, in my experience, once a chicken is dead laying in the coop the other chickens peck the dickens right out of it.  Two days later I walked in to find that same scene all over again.  And just five minutes ago I went out to the coop and found three more dead hens.  I'm ticked!  I'm puzzled too.  I need to find the cause of this and put an end to it fast.  I was concerned that maybe with the cold weather they weren't getting enough to eat, but I increased the amount of feed they were getting and they don't act like they are starving.  All of them look healthy and none had shown any signs of being otherwise.  It could be a water problem, perhaps, because I am having a tough time keeping the waterers from freezing up.  I'm going to change out their water more frequently.  It could be the cold, I guess, this is a colder than average winter so far, but last winter we had a few nights that were consistently below zero and even I think fourteen below with windchill, and I had no casualties last winter.  The other thing is that the two breeds of hens I've got out there are supposed to be well adapted to cold climates.  I think the other possibility could be rats.  We've got rats running around in those barns, and I know they would kill chicks and eat them, but I don't know whether or not they would eat nearly full grown hens.  I'm a little perplexed.  I applied some more rat poison to various locations around the place (no place that chickens have access) and am going to be much more frequent in my trips to the coop other than a time or two a day.  I am NOT a happy camper about this.  We will never have eggs if all of the hens die this winter.  UGH!!!