The Effects of Age on Breeding

Dear Dr. Lowder,

I am writing to you with a questions about a mares age and breeding. I have an 18 year old QH mare about 15.1 hands and I would like to breed her and I don't believe she has ever been bred before. I am wondering if it would be really hard on her to breed her at this age. She is in excellent health and is physically is in excellent shape.

Story originally posted by: Michael Lowder, DVM, MS

The only problem she has is navicular but she wears shoes all year round and doesn’t have any problems as long as she has shoes on. She is on no medication. I would like to know if you feel that it would be a bad idea to breed this mare and if I am putting both her and her baby in jeopardy because of her age. Thank you for your time and any advice that you may have would be greatly appreciated.


John Ainey

Dear John,

Although older, your mare is not too old to breed. If she does not appear to show signs of lameness with her shoes on this should not cause a problem. However, before you breed her you should have a veterinarian do a breeding soundness exam to evaluate her reproductive tract internally and externally. This way the vet can estimate the stage of her heat (estrous) cycle and the time of ovulation so you will know when she will be receptive to a stallion and the best time to breed.

Her reproductive tract can be palpated rectally and ultrasounded to determine if she may have problems with breeding and pregnancy. If any infection or abnormalities are present, they may be picked up on palpation or ultrasound. The width of her pelvic canal can be determined to see if she will have a likely easy delivery, however, this will also depend on the size of the foal. Her vulva should be evaluated to determine if she has a predisposition to being a “windsucker” which can easily be fixed with a simple procedure but can make her more likely to develop infection in her reproductive tract if not fixed.

A vaginal speculum can be used to visualize the most outer parts of the reproductive tract such as the vagina and cervix to determine if any problems are present. It may also be beneficial to culture her uterine fluid to make sure she is free of infection before breeding as well as biopsy her uterus. This is not painful to her and will help to tell you if she has a large chance of getting pregnant and carrying the baby to term. The breeding soundness exam is the best place to start if you want to successfully breed a mare that has not been bred before.

Thank you,

Dr. Lowder