Gelatinisation of starch in Nile tilapia feed

The aim of study was to observe the effect of different levels of starch gelatinization in feed for Nile tilapia. Wheat was extruded with different moisture addition (20%, 25%, 30% and 35%), to tentatively obtain different degrees of starch gelatinization. Five different diets were prepared one with raw wheat and remaining four with gelatinized wheat, using a pasta machine. The degree of starch gelatinization of the diets were assessed by Differential Scanning Calorimetry. All diets with wheat that had been extruded had completely gelatinized starch. The diets (Diets 1-5) were fed to fishes in 10 tanks with 9 to 11 Nile tilapia with a mean initial weight of 120 g for 30 days. Each diet was fed to fish in two tanks. The tanks were supplied with freshwater from a recirculated aquaculture system with a mean water temperature of 27°C. The fish were weighed at the beginning and at the end of the experiment. Daily dietary dry matter intakes were assessed; chemical composition in initial and final fish samples and diets were analyzed. Growth rates, feed conversion ratio, and retention of dietary protein and energy were calculated. The feed intake of fishes in each tank was on average 91 g per fish, which results in average weight gain of 78 g per fish. Regression analysis showed that the retention of dietary protein (p-value: 0.00821) and energy (p-value: 0.00821) were significantly related to second order polynomial of dietary treatment, however feed conversion ratio and feed intake were not significantly related. It was interesting to observe that at little addition of moisture as 20% in extruding wheat gave complete gelatinization. This shows the advancement in engineering in the field of feed manufacturing technology, which can be beneficial to feed producer and farmers.M-F