by Amanda Bradbery, Ph.D. Collaborator

Overfeeding Broodmares: How do you know when it’s too much?

Overfeeding Broodmares: How do you know when it’s too much?

The most common misconception in the horse breeding world is that we are feeding for two.

Thankfully for our wallets, we do not have to feed broodmares as if we are feeding two.  At least not until early lactation after the foal is born.  

The Problem With Overfeeding Horses

Obesity is all too common in horses in the U.S. and its effects are well-known: insulin resistance, equine metabolic syndrome, laminitis, etc.  And the consequences of obesity do not stop with the broodmare.

Are Obese Mares at Risk for Harming the Foal?

Obesity during pregnancy can have lasting effects on the foal.  What’s worse is that most of these effects do not become apparent until the foal matures into adulthood and enters a performance career.  The effects are strikingly similar to obese individuals.  Foals from obese or overfed broodmares have a higher risk of insulin resistance, equine metabolic syndrome, and laminitis, just to name a few.

What Happens to the Foal if I Overfeed My Mare?

Overfeeding and/or obesity in broodmares alters her hormonal levels, placental development, and nutrient transfer to the developing foal. This detrimental combination alters the foal’s tissue development and the expression of genes which control the foal’s mature metabolism.  

So how do you avoid overfeeding broodmares? Understand when the horse’s nutritional requirements increase! 

How Much Should a Pregnant Mare Eat?

A broodmare’s life is divided into 6 stages: 

  1. Open 
  2. 1st trimester of pregnancy 
  3. 2nd trimester of pregnancy 
  4. 3rd trimester of pregnancy 
  5. Early Lactation 
  6. Late Lactation

While nutritional requirements differ at each stage, knowing when and how to increase feed can ensure nutritional requirements are met without risk of restriction or excess.

That’s the key point here. You want to MEET your broodmare’s nutritional requirements, but not exceed or restrict.  

Where Should I Start With Feeding My Pregnant Mare?

With the horse body condition score system (BCS). 

To determine your horse’s nutritional status, you can use the well-established BCS scoring system (scale of 1 to 9; 1=emaciated, 9=terribly obese) which will help you assess body fat. The horse BCS scale was originally developed for use in broodmares, so it’s even more applicable here! 

For a pregnant mare, body weight is a less reliable measure of nutritional status when there is a growing foal, so taking the aerage of the amount of fat covering 6 areas of the horse’s body is a better solution. 

The ideal horse BCS for reproductive efficiency is 6, compared to 5 in performance horses.  This provides the broodmare with approximately 50 lbs. of additional fat cover which acts as a nutrient reserve for reproduction and fetal development.  

What to Feed a Pregnant Mare

1st and 2nd Trimester: During early pregnancy, there are typically no diet changes. Hay and grain should start to increase towards the end of the 2nd trimester to prepare for the 3rd and final trimester. 

 3rd Trimester: The 3rd trimester characterizes the greatest amount of fetal growth and a moderate increase in nutrient requirements.  This stage requires only a small increase in feed. Be careful to not overfeed during this trimester, as there is a significant risk of harming the developing foal’s metabolism. 

Lactation: How Much Should I Feed My Nursing Mare?

Early Lactation: The broodmare has the highest nutrient requirements right now than at any other stage of life! Underfeeding is significantly more of a concern than overfeeding at this time. However, proceed with caution. Increase the mare’s feed towards the end of the 3rd trimester in preparation for the drastic increase in intake. It’s always critical to feed broodmares with gut health in mind.  

Late Lactation: Feed can begin to taper off after the extreme increase in feed during early lactation. This stage often overlaps with early pregnancy in some horse breeding programs, but no worries because as you will remember, nutrient requirements do not significantly increase in the 1st trimester of pregnancy.

Mare and Foal Feed + Equine Probiotic Supplements

There are many excellent commercially formulated feeds on the market for pregnant and lactating broodmares, typically referred to as “mare and foal” feeds. Be sure to read the feed tag carefully when deciding how much to feed. It is best to consult an equine nutritionist for assistance. 

And remember, the gut microbiome plays a huge role in your horse’s overall health. Supporting your mare with specially formulated equine probiotics during this time of constant stress and change is a best practice for breeding farms.  

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