Effects of fat feeding and energy level on plasma metabolites and hormonesin Shetland ponies

The aim of this study was to investigate the influence of a fat-supplemente d diet compared with a carbohydrate diet on the lipid metabolism and the en teroinsular axis of Shetland ponies. The 'crossover' experiment was divided into two parts: in the first 10 weeks the diets comprised the correct numb er of calories according to requirements and in the following 10 weeks they were hypercaloric, in order to check the effect of a different energy cont ent of the diets. Feeding the fat-enriched diet, independently of its energ y content, led to a significant decrease in plasma triglycerides, associate d with a mean 50% increase of plasma lipoprotein lipase activity. After ora l glucose load the ponies on fat-enriched diets showed higher plasma glucos e concentrations. Oral glucose administration after feeding the hypercalori c fat-enriched diet led to a 25-fold increase of plasma insulin levels. Glu cose-dependent insulinotropic polypeptide plasma levels were increased in t he animals on the fat-enriched diets. The results of this study suggest tha t fat feeding improves triglyceride clearance. However, the fat supplementa tion of the diet also led to impaired glucose tolerance. These results are important for a better understanding of the function of the enteroinsular a xis. To investigate the influences of fat on lipid metabolism in relation t o the aetiopathogenesis of equine hyperlipaemia further studies involving d iseased animals are needed.