Thats awful! I`m so sorry to hear you lost her. I almost lost a colt tuesday night exactly the same way! If it hadnt been for the filly that had been born a few hours earlier not suckling and me in and out giving her colostrum he would have died too. When I heard grunting and gurgling in the stable behind the one I was in that didnt have a camera on in it coz I wasnt expecting her to foal yet, I ran like a lunatic to find him flaying about in the bag and it too was really thick and hard to break. What happened to you could happen to any of us at anytime, because we are human. I am definitely going to order a foal buzzer now to go along with my camera. Hopefully you will get another red and white filly next year.
I am so sorry. Hugs and prayers for you and Strawberry! It is so difficult to lose these precious babies. Give Strawberry lots of hugs and attention as she grieves for her baby.
As for your other mare that looks suddenly skinny but has milk--- she may be ready to foal! Many times when the foal gets into position for foaling, the mare will look much thinner. This one *could* be ready to foal at any time.