Avoid hay with nonstructural carbohydrate content of greater than 16%
Researchers at the University of Minnesota 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). The study objectives were to determine if there is a difference in blood glucose and insulin response to feeding hay types with varying NSC content between horses with PSSM and control horses.
Horses' glucose and insulin levels were measured after feeding hay with high (17%), medium (11%), and low (4%) NSC content. In the control horses, significantly higher insulin responses were observed when horses were fed high NSC hay, but the blood glucose levels did not differ.
In the PSSM horses, a greater insulin response to the high NSC hay compared to medium or low sugar hay was detected, 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.
Researchers suggest that owners or managers avoid feeding PSSM horses hay with an NSC of greater than 16 %; they recommend hay with less than 11% NSC for these horses because it does not produce a significant elevation in blood sugar or insulin. Analyzing your hay for quality will determine NSC content.