I Want To Breed My Mare

I want to breed my mare is a common statement heard this time of year. This statement is often followed by but what do I need to do? While hoping for a simple answer, the return response is often a series of questions. How old is she? Is she currently pregnant? Has she had foals before? How many foals has she had? When was her last foal born? Has she been bred before, but did not conceive or has she lost a foal during pregnancy? Does she have a history of twins or placentitis? Have you seen her showing signs of estrus yet? Do you want to breed her with live cover or artificial insemination? If using artificial insemination, are you going to use fresh-cooled semen, or frozen semen? When do you want the foal to be born? Based on the answers to these types of questions we are hopefully finally able to answer your question of what do I need to do? All these questions provide us with valuable information to help you make an informed decision on what the next step is to successfully getting your mare pregnant.

Another common question is, when is my mare too old to breed? I would consider the optimal age for breeding your mare is between 4 and into their early teens.  These young mares are more likely to be easier to establish a pregnancy in, but factors such as overall and reproductive health of the mare and potentially the number of pregnancies the mare has carried up to this point may play an important role in her fertility. I don’t know that there is a set answer for what age to stop breeding your mare. When she reaches her late teens and into her 20s the health and safety of the mare need to be considered along with potentially decreased conception rates in these older mares. When we think of these older mares we certainly need to consider what the physical stress of carrying and delivering the foal will be on that mare if she does conceive.

In order to help determine if your mare is ready to be bred, a good physical exam will be beneficial. A mare that is excessively fat may result in lower pregnancy rates. Mares that are excessively thin or have chronic pain may fail to cycle, or have higher rates of pregnancy loss due to early embryonic death. Ensuring that the mare is in appropriate body condition and a good plane of nutrition prior to breeding will improve your chances of getting her in foal and her staying in foal. Evaluating the conformation of her vulva may help us determine the likelihood of her getting pregnant. Poor conformation of her vulva is not an eliminating factor, but something we need to be cognizant of and manage the mare appropriately during the breeding and post-breeding process.

A breeding soundness exam consisting of rectal palpation and ultrasound, vaginal exam, uterine culture and cytology, and possibly a uterine biopsy are useful diagnostic tools to help you determine if your mare is ready to breed. Performing these diagnostics helps us let you know where she is in her estrous cycle, helps makes sure she does not have a uterine infection, and gives us an indication of the overall health of her uterus. Using the information collected we are able to make better decisions when answering your question, I want to breed my mare, but what do I need to do? You may be advised that the mare has a uterine infection that needs to be treated first, or that you might be better off flushing embryos from her and letting a recipient mare carry the baby.

Ultimately, you as the mare owner and we as your veterinarian have the same goal, and that is to achieve a pregnancy that results in a healthy foal. Working together throughout the process will help you both achieve that goal.

By Jason Grady, DVM, MS, DACVIM 
Courtesy of Kansas State University