Optimization of commercial feed extrudates characteristics: Effects of preconditioner conditions and sunflower meal inclusion on the growth performance and health status of Nile tilapia

The aim of this study was to optimize the preconditioner conditions of commercial scale extruder to increase the inclusion of sunflower meal (SFM) in the tilapia diet. A Box–Behnken design was employed to evaluate the effects of three independent variables, i.e., the substitution of soybean meal (SBM) protein with sunflower meal protein (0, 25 and 50 %), the preconditioner temperature (85, 95 and 105 °C) and the preconditioner moisture (15, 17.5 and 20 %), on the physical properties of the extrudates. The optimal values for unit density, expansion, the sinking %, Holman durability index, dietary cellulose and lignin were statistically suggested to be reached at a preconditioner temperature of 100 °C and the inclusion of sunflower meal in the extrudates up to 30 % soybean meal protein. On the basis of the Box–Behnken results, four runs were used to examine the effect of soybean meal protein substitution (0.50 %) with sunflower meal protein, where the different formulations were processed under different preconditioner temperature (85 °C, 105 °C). Nile tilapia (initial weight of 47 g ± 7.6, 28 fish per group) were randomly distributed into fiberglass tanks (1000 liters) to form four treatments. The preconditioner temperature and substitution factors had no significant effect on growth performance or feed utilization, except for FI, FCR and PER. High preconditioner temperature neutralized or reduced the negative effects of soybean meal on the gut health status. The lesion score of tilapia liver suggested that SFM had a less negative effect than SBM. These results support the promising trend of increasing sunflower meal levels in aquafeed.