Thermal stability of vitamins A and E in rations and vitamin premixes for shrimp/Estabilidade termica das vitaminas A e E em racoes e premixes vitaminicos para camaroes

The study aimed to evaluate the thermal stability of vitamins A and E on different rations and vitamin premixes used in shrimp farming. Three commercial rations pelleted and disintegrated in two different diameters and two vitamin premixes were used in the experiment. Samples of each ration and premixes were placed in plastic containers and stored under the following conditions: refrigerated environment (6[degrees]C[+ or -]2[degrees]C), acclimatized environment (20[degrees]C[+ or -]3[degrees]C) and greenhouse environment (40[degrees]C[+ or -]3[degrees]C). The levels of vitamins were determined in triplicate in samples at times 0 (control), 5, 10, 15, 20, 25 and 30 days, under the conditions described above. The results were statistically treated by analysis of variance (ANOVA) and the Duncan test was applied at 5% probability. The results showed that the average vitamin A percentage losses in rations were 65%, 60% and 68% for climatized, air-conditioned and greenhouse environments respectively. For the vitamin premix A the percentage of degradation was 78-87% and it was observed higher losses in the climatized and greenhouse environments. With respect to vitamin E, it was observed in the rations lost of 88% to 100% verifying the total losses for the storage in air-conditioned and greenhouse environments. For the vitamin premix E the losses were 71% to 82%. It was concluded that during the storage of feed and premixes vitamins, losses due to thermal degradation showed lack of stability of fat soluble vitamins in the structure of feed and premixes used in feed for shrimp.