Effects of oat processing on the glycaemic and insulin responses in horses

This study was conducted to evaluate the effects of different oat processing techniques on the plasma glucose and insulin response in horses. In a cross-over design, six horses (ages 4-15 years, mean body weight+/-SD: 450+/-37 kg) were fed in random order: untreated oats, finely ground, steam-flaked and popped oats. The total oat intake varied between 1.05-1.5 kg/day, and the amount of diet was adjusted to a starch content of 630 g starch per day and horse (1.2-1.5 g starch/kg BW/day). During the stabilization period of 10 days, horses additionally received 6 kg grass hay. Following this adaptation period, plasma glucose and insulin responses to the respective dietary treatments were tested. Horses were fed their test diet (exclusively oats), and blood samples were collected at defined times to determine glycaemic and insulin response. Oat feeding resulted in a significant increase in mean plasma glucose and insulin concentration. However, glucose and insulin peaks as well as their respective areas under the curves were not clearly influenced by oat processing. The glycaemic index varied between 94.7+/-11.2% (steam-flaked oats) and 102.6+/-14.5% (finely ground oats, n.s.), the insulin index ranged between 93.8+/-18.9% (popped oats) and 150.0+/-77.6% (finely ground oats, n.s.). The insulin reaction to oat feeding showed a high variability between the horses. The results of this study indicate that the glucose and insulin responses are not clearly altered by the different types of oat processing. However, the glucose and insulin responses tended to be lower in thermally treated oats when compared with untreated or finely ground oats.