If your horse has such a heavy infestation of worms that she's passing adult ones in her faeces then she could well have damage of the intestinal lining.

If worming has been neglected then it might be safe to presume there's been other owner neglect.  When were her teeth done?  Did you have a ppe done? Bloods drawn? Anaemia may indicate a serious worm burden which will lead to her losing weight and struggling to get maximum benefit from nutrition. 200lbs is a lot to be underweight.    As such you'd be well advised to ask your vet to thoroughly check her over and to advise on nutrition in the light of her infestation and potential problems caused by that.

Last Edited By: Spooksandbolts Nov 23 12 8:40 AM. Edited 2 times.