Evaluation of Apparent Nutrient Digestibility of Novel and Conventional Feed Ingredients in Sobaity Seabream (Sparidentex hasta) for Sustainable Aquaculture

This study aimed to evaluate the apparent digestibility coefficients (ADCs) for nutrients and energy of seven conventional and alternative feed ingredients (poultry feather meal, fermented feather meal, mealworm meal, defatted black soldier fly, Chlorella, poultry by-product meal, and corn meal) when fed to Sobaity seabream (Sparidentex hasta), with the goal of identifying sustainable, digestible, and nutritionally viable ingredients for aquaculture feed formulations. A reference diet (RF) was formulated to meet the nutrient requirements of Sobaity seabream while test diets were prepared to contain 70% RF and 30% of the test ingredients. Sobaity seabream (200 ± 8.0 g) were fed the diets for seven days before fecal matter was collected by stripping. The whole length of the digestibility trial was 21 days. The ingredient apparent digestibility of dry matter (34.8–70.4%), crude protein (52.8–107.8%), crude lipid (67.7–112.9%), and energy (52.2–86.1%) were affected by test ingredients (p < 0.01). The dry matter digestibility of mealworm meal was the highest (70.4%) compared to other ingredients. Feather meal, Chlorella, and black soldier fly meal had significantly lower values of dry matter digestibility. Dry matter and crude protein were significantly more digestible in fermented feather meal than the feather meal without fermentation. The crude protein digestibility was significantly higher (107.8%) for mealworm meal. However, feather meal has shown a significantly lower value (52.8%) for crude protein digestibility compared to other ingredients. Energy digestibility showed a significant positive correlation with dry matter digestibility (r = 0.870). The energy digestibility of mealworm meal was significantly higher (86.1%, p < 0.05) than other ingredients. Feather meal had the lowest energy digestibility (52.2%) with no statistically significant difference from Chlorella, corn meal, and black soldier fly meal. This study indicates that mealworm meal is the most easily digestible protein source for Sobaity seabream and should be prioritized in their diets. Fermentation enhances the digestibility of feather meal and is recommended when using it. Ingredients with a lower digestibility, like feather meal, chlorella, and black soldier fly meal, should be used in moderation or undergo further processing to improve nutrient availability.