Reasons for performing study: Quarter Horses are particularly susceptible to polysaccharide storage myopathy (PSSM). Nutritional therapy and possibly prophylaxis includes fat-supplemented diets whilst starch supply should be kept to a minimum.
Objectives: To investigate the glycaemic and insulinaemic response of clinically normal Quarter Horses to concentrates high in fat and low in starch.
Methods: Twelve Quarter Horses were studied. The precondition for inclusion in the study population was that the horses had not shown clinical signs of myopathy. The Quarter Horses were fed according to a 4 x 4 Latin square design haylage plus isocaloric concentrates based on barley and oats as control (CO), sugar beet pulp, grass meal and soybean oil (SB), rice bran and grass meal (RB) and rice bran, grass meal, sugar beet pulp and soybean oil (CP), each over 2 weeks after 1 week of adaptation. At the end of each period, 1 kg of concentrate was fed and blood sampled 0, 30, 60, 90, 120, 180, 240, and 300 min post prandial (ppr.). Creatine kinase (CK; 0 min ppr. only), glucose and insulin were analysed. Glycaemic and insulinaemic index was calculated from each concentrates area under the curve (AUC) relative to CO.
Results: Rice bran containing concentrates were partially refused at the beginning of the trial periods. CK activity, and glucose and insulin patterns (ppr. mean, peak, AUC, index) were highest with CO (P<0.05). The correlation between glucose and insulin (P<0.001) ranged from r = 0.570 (CO) to r = 0.364 (RB). Basal CK was highly correlated (P<0.001) to the mean ppr. plasma glucose.
Conclusion: Rice bran, sugar beet pulp, grass meal and soybean oil are suitable to include in concentrates that induce low glycaemic and insulinaemic response. Its acceptance seems to be a question of habituation. Although the mechanism is not completely understood, glucose patterns and basal CK activity are highly positively correlated. Both were affected by the type of concentrate used.
Potential relevance: Results support the suggestion that low-starch and high-fat feeding may be helpful not only in the nutrition of affected horses, but also to prevent future PSSM associated discomfort in particularly susceptible horses.