AAEP Ask the Vet: Broodmare Practices for the Healthy and Subfertile Mare

Broodmare Practices for the Healthy and Subfertile Mare


  1.  How can I prevent my mare from getting bred by my stallion as they are extremely buddy sour? We have tried separating them but I feel it becomes a dangerous situation for them

I have given some thought to your troublesome situation. This is an interesting topic for discussion. I see two immediate concerns for you: 1) wanting to avoid physical trauma to both your mare and stallion and 2) not wanting your mare to get bred.

Equine intercourse is a rapid and sometimes violent act. All parties are at risk for trauma during this activity. Furthermore, stallions often get injured when exposed to mares that are not in heat when the mare objects strongly to the stallion’s advances. Letting your mare cohabitate with your stallion could result in trauma to both your mare and stallion at any time and also result in an unintended pregnancy.

If your stallion has a busy breeding season, you may want to have more control over his activities. An injury can really set things back with your stud book. Additionally, if his fertility is sub-optimal you will not want him wasting his “efforts” on breeding your mare if that is not your desired goal. Some stallions need to be on a specific collection schedule to optimize conception for the mares that he is booked to.

There are a few chemical, non-chemical and surgical methods available to reduce conception in the event that a mare will be, or has been, exposed to a stallion. Unfortunately, none of them are foolproof in either preventing conception and/or eliminating estrus behavior during which time your mare will be agreeable to being bred. Some of the methods may reduce the odds of conception, but will not effectively suppress estrus, thus your horses will likely be breeding. Some methods may suppress estrus, but I have found that horses behave with a “where there is a will there is a way” attitude. For example, I have seen some determined stallions try to breed a mare over a fence. Because of these inherent behavioral challenges, most farms that house stallions keep them completely segregated from other horses on the farm.

The equine sex drive and resulting complications in management are the leading reason for the considerable castration rate among males. If your intent is not to retain your stallion as a breeding animal, I would strongly encourage you to castrate him. Likewise, you could ovariectomize your mare. Removing the ovaries from the mare will make her infertile. Interestingly though, ovariectomized mares will often show persistent mild estrus, which might make your stallion a very busy boy. I realize that castrating your stallion may not be an option, but this would likely solve that vast majority of your concerns.

Alternatively, I would encourage you to consider changing your buddy system by adding another mare for your mare and possibly a goat or other type of buddy for your stallion. I have seen arrangements such as these prove very useful. If you are willing to consider separating your mare and stallion, there is another idea to consider. The risk of injury during this adjustment period may be mitigated by the use of long acting and short acting tranquilizers to get them over the separation anxiety.

In any circumstance, I would encourage you to seek input from your farm veterinarian. Your veterinarian should have a good understanding of your goals, management options, know your horse’s personalities and be able to administer appropriate treatments based on what would work best for all of you. Best of luck to you! Holly Mason, DVM, MS, Utah State Veterinary 


2.   I have a 2-year-old Molly mule that shows strong estrus behaviors. Will implanting marbles in her uterus help? Or are herbal supplements or other therapies preferred? Cost is a factor. 

I have a real soft spot for these creatures and I applaud you for being a mule owner. Your situation is not unique to molly mules. Dealing with undesirable estrus behavior can be a problematic situation for the owner of any female equid.

Marbles have been used to suppress estrus with mixed results. Some authors report that timing the placement of the marble as close to ovulation as possible has a positive influence on the efficacy. The uterus is also surprisingly good at expelling the marble. These reasons have made marble use overwhelmingly unpopular among horse owners and veterinarians. That being said, the marble would likely be your least cost interventional option.

The most reliable method to suppress estrus is by administering synthetic progesterone. You have two options in this category. The first and most reliable is to administer an oral solution (Regumate) daily. This can be costly and there are human health risks associated with exposure to this product. The second is by administering an intramuscular injection of a compounded long acting progesterone. Depending on the formulation, the injection may need to be repeated every 2-4 weeks. My experience has been that the injectable method is slightly less effective than the oral method. A lot of what determines the treatment depends on the client’s budget and level of expectation. I have used both methods with very acceptable results.

You may hear some people talk about spaying a molly mule. This is a procedure during which the ovaries are removed. I would caution you against this procedure as it rarely eliminates the estrus behavior and in fact often makes it worse.

A no cost method of dealing with your molly mule’s estrus would be to track her cycles on the calendar and limit or reduce your demands on her during times when you know she will be in heavy heat. As a point of reference, most mares are seasonal breeders that begin cycling in early spring and go into winter anestrus around late fall. Ovulation occurs about every 21 days and heat is evident for 5-7 days around the time of ovulation.  

I sympathize with your situation and hope you can find a method that works for you. Good luck! Holly Mason, DVM, MS, Utah State Veterinary 

3.   I have a 5-year-old mare that both her front knees have swelled like tennis balls. What can be applied topically to alleviate the swelling? My second question is that I have another mare (English Thoroughbred) that was coverd twice from a stallion in pakistan. The mare did not concieve in two cycles after a period of 21 days. The veterinarian has ultrasounded the mare and says there is a folicle, which burst after 4 days in which she came back into heat? Any suggestions on what I should do for the mare before she is covered again by the same stallion? 

In regards to your mare with the swollen knees, a diagnosis needs to be determined by a veterinarian in order to decide the best course of treatment. In my experience, the swelling you are describing is unlikely to be relieved by any type of topical treatment alone. Depending on the diagnosis, treatment may include any combination of systemic anti-inflammatory drugs, disease modifying osteoarthritis drugs, intra-articular medication, topical therapy or possibly even surgery. The course of treatment is typically negotiated between the client and veterinarian depending on the diagnosis and expectations of the client in terms of outcome.

In regards to your broodmare, it is not uncommon for a mare to require 2-3 covers prior to conceiving. If you think there is a problem, I would advise having a uterine culture and cytology performed to make sure that there is not an infection present. If her culture and cytology are supportive of an infection, that will need to be addressed with antimicrobial therapy. Most veterinarians will use an ovulation induction agent, such as Deslorelin, to ensure that the mare will ovulate at an appropriate time following breeding to improve the odds of conception. The timing of the administration of this drug is critical and depends on many features of the rectal palpation, ultrasound exam and when the stallion covers her. For the mare that has an over active or prolonged inflammatory response during which fluid is retained in the uterus, intramuscular oxytocin injections are commonly used to encourage evacuation of that fluid. Some mares can be quite challenging to get pregnant and may require additional therapies not mentioned here. I hope you have better luck the next time around. Holly Mason, DVM, MS, Utah State Veterinary 

4. I have just bred my Andalusian mare and am assuming she is in foal. How should I manage     her forage intake to be sure she gets appropriate nutrients and roughage? She is a very, very easy keeper that can easily get fat on hay alone.

This is an excellent question. I am glad that you have given this aspect of your management some consideration. The good news is that if she is already at a reasonable weight and body condition score (BCS), you don’t need to make changes to your feeding program until she finishes her 8th month of gestation. The time of highest digestible energy requirement for a broodmare is during months 9, 10 and 11 of gestation and then through lactation. Energy requirements are even higher during lactation, than they are during gestation.

Forage is the primary feed material required by any horse and a broodmare is no different. Forage consists of dry hay and/or fresh pasture. A good rule of thumb is to keep it simple. Start by giving your mare a thorough looking over to determine her current BCS. The ideal BCS for the average horse is 5/9. However, Andalusians tend to be on the plump end of the spectrum. I believe it would be appropriate for your mare to sit somewhere around a 6-7/9.  It has been my experience that when mares are obese (8-9/9) towards the end of their gestation that they are prone to a more challenging delivery. Obesity also has a negative impact on fertility. You will want to be aware of this if you are planning on re-breeding her.  In addition to BCS, you should document her weight by using a weight tape. Weight tapes are a reasonable method to estimate a horse’s weight. If you use the same tape consistently, you will be able to document changes in your measurements. At certain intervals you should repeat the body condition scoring and weight taping to evaluate if she is gaining or losing weight and to determine if your feeding program is meeting her needs.

When you are feeding a horse to maintain it’s current weight, you should aim to feed approximately 1.5%-2.0% of your horse’s body weight per day. So, if your mare weighs 1200 pounds she should be fed 18-24 pounds of hay daily. I encourage you to weigh your mare’s feed if this is something that you are not already doing. This is the most accurate way to make sure your mare will not be over or under fed. Volume measurements (i.e. a quart or a flake) are not consistent between feed materials.

Easy keepers on good quality hay may benefit from a vitamin/mineral balancer added into the diet. There are several vitamin/mineral balancers available from reputable companies on the market today. This is important to consider because as hay ages the vitamin content will decline over time. The mineral content of your hay will typically vary depending on the type of hay and the quality of the soil it was grown on. Additionally, all horses need free choice salt and fresh water available at all times.

If you wanted a more precise determination of what to feed, you could have your hay sampled and analyzed to evaluate specific constituents such as digestible energy, protein and vitamin/mineral content. For example, alfalfa hay is very high in digestible energy and protein compared to grass hays that are typically lower in both of these categories. Thus, you may need to feed less alfalfa or more grass hay depending on your situation. You could have your veterinarian or a nutrition consultant balance a ration for your mare with the information from a hay analysis. At the very least, you should make a gross evaluation of your hay for quality. Make sure it smells and feels pleasant, is not dusty, is not moldy and there are little to no weeds or debris that have been baled into it.

If your mare is at a reasonable body condition on your current feed program, then you should not need to make any changes until she ends her 8th month of gestation. At this important time, you should add a concentrate to her forage intake. A concentrate is a way to get additional calories, protein, vitamins and minerals into your mare as the foal’s needs are increasing in-utero and while nursing. There are also several reputable companies that produce and market such concentrates. Remember to read the label for the feeding instructions. The label will usually give you an idea of how much to feed on a daily basis depending on your mare’s BCS, weight, stage of production and forage availability.

Use your veterinarian as a resource to help you determine your mare’s weight, BCS and advise on your feeding program. You will be seeing your veterinarian often during the pregnancy for repeat pregnancy evaluations and immunizations that are important during gestation. Good luck! Holly Mason, DVM, MS, Utah State Veterinary 

 5. My mare is due in early July. I am from North Dakota and have vaccinated her now, but have heard that it is good to vaccinate again within 30 days of foaling to give the foal resistance. What about the rabies shot? Should that be done within that 30 day timeframe, or now when I usually do it?

The short answer to your question is yes – booster the rabies immunization. The ability of the foal to fight off illness is profoundly dependent on the immunoglobulins that are passively acquired by consuming the Dam’s colostrum during the first 18-24 hours of life. The reason for the recommendation to booster all of the mare’s immunizations 4-6 weeks prior to the delivery date is to ensure that the highest quality colostrum possible will be available to her foal. The immunity acquired by the foal through the colostrum will be what provides protection during most of the first year of life.

De-worming should also be part of your preventative care strategy for both mare and foal. There are differing recommendations on when to de-worm a broodmare. The foal will naturally consume the mare’s manure to establish gut flora and you will want to limit the foal’s exposure to parasites during this time. Most broodmares will get de-wormed at the same time they get their pre-foaling immunizations and then possibly again more near the delivery date.

Don’t forget to have your veterinarian perform a post-natal exam on your foal on that first day of life. I can not stress enough how important this is!! Part of the exam will be to determine if the foal has received enough antibodies from the colostrum. Foals that have not received enough antibodies are at significantly higher risk of illness. Good luck! Holly Mason, DVM, MS, Utah State Veterinary