Ask the Vet: Broodmare Practices

Courtesy of AAEP
Answered by, Holly Mason, DVM, MS, Utah State Veterinary 

Question: 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.

 Answer: 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.