My 15 year old draft mare who is 5 months pregnant has developed swelling above the udders and forward towards her navel. It is only on the left side and her teets are not draining but they have a clear fluid with a little viscosity that you can milk. The vulva is not draining at all. Temperature has been normal and have been checking it at least twice daily. The vet was out and started her on antibiotics and banamine for the moment. He said it looked infected but showed no edema or heat. He also palpated the foal which he said was still going good. Spoke to the vets office today and they advised the blood tests all came back normal but would get back to me. She is fecal tested 4 times per year and wormed 4 times per year. I also spoke to the previous owners who haven't heard of it either. The only dramatic change lately was 4 mares left the field she was in within the last month for other barns. She now is in with one other mare who is about 22 and a 23, 24 or 25 year old gelding. Has anyone had anything similar and if so what was the outcome? I am attaching a photo but not sure how good it shows it.