I have a 24 year old Walking Horse mare that has always been healthy. I have had her since she was 5. She did have a foal before I bought her but that is all. Yesterday I went to clean out between her nipples and the right side is a huge growth or swelling. I am not sure which it is, it feels like a long, large tube of something. I don't know if it is a swollen mammory gland or something else. She is not tender, still eating fine and no temperature. I am not sure when it appeared either as I don't check her every day. It could have been there for awhile. I am calling the vet today as soon as they open, but just wondering if anyone had any similar experience. I am praying it is something simple.