Effects of Obesity on Mares’ Follicles and Oocytes

Researchers found that obesity appears to negatively impact mares’ follicles and oocytes and, thus, their fertility.

No account yet? Register


It’s no secret: Equine obesity levels are on the rise. While all overweight horses need to drop a few pounds, you might want to pay special attention to the particularly chubby broodmares gobbling up grass in your pastures—especially if you’re hoping for a foal this spring. Researchers have confirmed that obesity appears to have negative effects on mares’ follicles and oocytes.

Dawn Sessions-Bresnahan, MS, PhD, an assistant professor in the Berry College Department of Animal Science, in Mount Berry, Georgia, worked with colleagues at Colorado State University, in Fort Collins, to determine if increased body weight affected reproduction.

The researchers used 16 nonlactating mature mares with body conditions of either 5.1 (10.5% body fat) or 7.9 (16.2% body fat) on the 1 to 9 scale. The former mares were considered controls and the latter ones were classified as obese. When the researchers detected a follicle greater than 35 millimeters with uterine edema (fluid swelling indicative of impending ovulation), they administered a gonadotropin-releasing hormone analog to help the follicle mature.

Approximately 22 to 24 hours after administration, the team collected the oocytes (immature egg cells), granulosa cells (which surround developing ovarian follicles), and follicular fluid (which is released during ovulation) from each follicle. On the same day, the team collected blood samples prior to morning feeding to evaluate mares’ levels of glucose, insulin, leptin, adiponectin, and other metabolites

Create a free account with TheHorse.com to view this content.

TheHorse.com is home to thousands of free articles about horse health care. In order to access some of our exclusive free content, you must be signed into TheHorse.com.

Start your free account today!

Already have an account?
and continue reading.


Written by:

Kristen M. Janicki, a lifelong horsewoman, was born and raised in the suburbs of Chicago. She received her Bachelor of Science degree in Animal Sciences from the University of Illinois at Urbana-Champaign and later attended graduate school at the University of Kentucky, studying under Dr. Laurie Lawrence in the area of Equine Nutrition. Kristen has been a performance horse nutritionist for an industry feed manufacturer for more than a decade. Her job entails evaluating and improving the performance of the sport horse through proper nutrition.

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from TheHorse.com

Sponsored Content

Weekly Poll

sponsored by:

When do you begin to prepare/stock up on products/purchase products for these skin issues?
97 votes · 97 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with TheHorse.com!