Equine insulin resistance—a condition in which cells fail to respond normally to the hormone insulin—requires careful dietary management to prevent laminitis and other complications from developing. So it's no surprise that both veterinarians and horse owners are on the lookout for new ways to help manage this disorder.
Case in point: Researchers from Colorado State University (CSU) recently tested the effects of n-3 polyunsaturated fatty acids, or n-3 PUFAs, on glucose and insulin dynamics in horses. Previous research in other species showed that n-3 PUFAs can improve insulin sensitivity, and n-3 PUFAs from marine sources, such as fish or algae, appeared to improve glucose transport from the blood into the cells.
For the current study the researchers, led by Tanja M. Hess, MV, MSc, PhD, assistant professor of equine sciences at CSU, employed 21 nonpregnant mares of mixed stock horse breeding. The mares consumed a diet of free-choice alfalfa/bromegrass hay for one month before the researchers grouped the horses by age, body weight (BW), and body condition score (BCS) and randomly assigned them to one of three treatments:
- CON—These horses consumed a control diet, consisting of rolled barley and alfalfa/bromegrass hay, containing no supplemental PUFAs.
- MARINE—These horses consumed a control diet supplemented with a commercial algae/fish oil pellet to provide 38g of n-3 PUFAs.
- FLAX—These horses consumed a control diet supplemented with ground flaxseed to provide 38g n-3 PUFAs.
The team housed the horses in drylots for the duration of the 90-day treatment period and recorded horses' BW and BCS on a monthly basis. The team also measured horses' insulin response using an intravenous glucose tolerance test at Days 0, 30, 60, and 90. Based on baseline insulin sensitivity, the team classified horses as being either insulin resistant (IR, n=11) or normal (n=10).
n-3 PUFA Effects on Glucose & Insulin: The researchers observed no differences between blood glucose levels or insulin's ability to respond to glucose in horses receiving the CON, MARINE, or FLAX treatments.
n-3 PUFA Effects on Insulin-Resistant Mares: The team found that the eight IR horses in the MARINE (n=5) and FLAX (n=3) groups showed improved insulin sensitivity during the 90-day treatment period compared to horses in the CON group. Although scientists do not know the exact mechanism for this reduction in insulin resistance in horses, research results from humans and rats suggest that decreased inflammation, increased adiponectin (a protein) secretion, and increased transporter function in skeletal muscles are all viable causes.
Overall Glucose and Insulin Dynamics: Insulin sensitivity increased from Day 0 to Day 90 across all treatment groups, and correlated slightly to body condition score (as body condition score decreased, the horse’s sensitivity to insulin increased regardless of their assigned dietary treatment).
Take-Home Message
The team concluded that n-3 PUFA supplementation appears to improve insulin sensitivity in IR horses. They noted that future studies, with controls for breed, age, and sex, could help researchers better understand the relationship between n-3 PUFAs and insulin resistance.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.