Effects of Hay Carbs on PSSM Horses Examined

University of Minnesota researchers have been examining the effects of feeding horses hay with varying levels of nonstructural carbohydrate content (NSC) in order to determine the best diets for horses with polysaccharide storage myopathy (PSSM). Lisa Borgia, a PhD candidate under the direction of Stephanie Valberg, DVM, PhD, Dipl. ACVIM, presented study results at the 2009 Equine Science Society Meeting, held May 29-31 in Keystone, Colo.

The study group's objectives were to determine if there is a difference in blood glucose and insulin response to feeding hay types with varying water soluble sugar and starch (NSC) content between horses with PSSM and control horses.

Researchers sampled the horses' glucose and insulin after feeding hay with high (17%), medium (10.6 %), and low (4.4%) NSC content. In the control horses they found significantly higher insulin responses when they fed high-sugar hay, but the blood glucose levels did not differ.

In the PSSM horses the researchers detected a greater insulin response to the high-sugar hay compared to medium or low sugar hay, but this group's insulin concentrations were less than the controls on high-NSC hay.

Blood insulin response appears to be a more sensitive indicator of the metabolic effects of high-NSC hay than glucose response.

The researchers suggest that owners or managers avoid feeding PSSM horses hay with an NSC of greater than16 %; they recommend hay with less than 11% NSC for these horses because it does not produce a significant elevation in blood sugar or insulin.

About the Author

Kathryn Watts, BS

Kathryn Watts, BS, is the director of research for Rocky Mountain Research and Consulting and a passionate forage researcher. Her web site is www.safergrass.org.

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