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Does spaying your pet rat decrease her chances of developing mammary tumors? Yes, because it takes away the ovaries and decreases sex hormone production. Mammary tumors in rats are sensitive to prolactin, which has a pituitary component for the stimulation to tissue sensitive to sex hormones. Mammary tumors may spread through the lymph node chains. Many tumors can grow very large and be life threatening. Many grow slowly, but cause the rat problems with movement. Mammary tissue is spread on the underside of the rat with some extending up their sides and onto their backs, so virtually tumors can be found almost anywhere on the rat. The sooner the mass is removed the better - it is far better to get it while it is small and freely moveable. The most difficult part of the surgery is actually after the surgery: keeping the rat from pulling out its sutures and/or staples. Good pain medications sent home decrease the likelihood of your rat removing the sutures/staples. In some instances a nasty tasting ointment is sent home to put on the incision. In some cases depending on where the incision is, an Elizabethan collar may be worn to prevent the chewing of the incision line. The tissue removed can be sent in to the pathologist to tell exactly what type of tumor has been removed - this might have a bearing on prognosis and if recurrence is likely.

I prefer to spay young females as soon as they've reached 200 grams. The younger and more slender the rat is, the easier the surgery is on her. I can also use an alternative technique called the flank approach which minimizes any post-operative chewing of a major incision line. A spay can be done on an older or heavier rat as well, it will just require an abdominal incision and can be more problematic. Both techniques are commonly used. Schedule your female rat! 

Cathy Johnson-Delaney, DVM
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