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This study describes the process of developing an enzymatic pretreatment to improvethe nutritional value of feather meal (FeM). In a first experiment, a full factorial design was used toexamine the effects of various incubation conditions on the solubilization of nitrogen in FeM. Weincubated FeM for 3 h with various levels of a commercial alkaline serine protease (Savinase®16L), sodium sulphite (Na2SO3), and digestion buffer. A Savinase® 16L level of 3% (%FeM v/w),Na2SO3 level of 3% (%FeM w/w), and digestion buffer level of 500% (%FeM w/w) were identifiedas the optimal conditions. Under these optimal conditions, 45% of the nitrogen in FeM wassolubilized. In a second experiment, we evaluated the effect of more economically sustainableincubation conditions on the in vitro digestibility of protein (pepsin-HCl digestibility andmultistep protein evaluation) in FeM. Two FeMs were incubated with 0.5% Savinase® 16L (%FeMv/w), 2% Na2SO3 (%FeM w/w), and 200% buffer (%FeM w/w) for 24 h. The pretreatment improvedpepsin-HCl digestibility by 7%–16% and the total tract degradable protein content by 14%–50%.Accordingly, this novel pretreatment could be applied in the animal feed industry to improve thenutritional value of FeM.

Simple Summary Aquaculture is the world’s fastest growing sector of the global food system. Aquaculture feed producers are seeking substitutes for fishmeal and fish oil to develop more sustainable feeds. Marine microalgae show promise as potential ingredients in aquafeeds; however, the literature lacks data on the digestibility and availability of macronutrients and individual fatty acids for omega 3-rich microalgal biomass, Schizochytrium spp., in rainbow trout. This is an important gap to fill because, among marine microalgae, this species is the most frequently used in fish feed, particularly as a dietary supplement or mixed with other ingredients; digestibility data would guide more judicious inclusion of this microalga biomass. High digestibility of macronutrients, energy and fatty acids showed that Schizochytrium spp. is a high-quality substitute for fish oil and potential candidate as a supplement of LC-PUFA in trout feed with vegetable oils. Digestibility is influenced by temperature and several trials have shown increased macronutrient digestibility with increasing temperature. There is an urgent need to determine the effect of temperature on lipid and fatty acid digestibility. We found that the digestibility of nutrients in rainbow trout maintained at 8 °C or 15 °C was not significantly different. However, the digestibility of DHA omega 3 was significantly higher at 8 °C than at 15 °C. Abstract Aquaculture feed formulation has recently turned its focus to reduce the reliance on marine-derived resources and utilise alternative feedstuffs, as an approach to improve the environmental sustainability of the aquaculture sector. The fish oil market is highly volatile, and availability of this commodity is continuously decreasing for use in aquaculture. Currently, a growing number of commercial efforts producing microalgae are providing omega 3-rich oil for sustainable aquaculture feed. This study was focused to determine the nutrient digestibility of a marine microalga, Schizochytrium spp., which is rich in docosahexaenoic acid (DHA) and long-chain polyunsaturated fatty acids (LC-PUFA), as a novel dietary lipid source that could be utilized effectively by rainbow trout (Oncorhynchus mykiss). A whole-cell Schizochytrium spp. biomass was used in the digestibility experiment at two different temperatures, 8 °C and 15 °C. No significant differences were detected between the two temperatures for the apparent digestibility coefficients (ADCs) of the dry matter (94.3 ± 4.9%), total lipids (85.8 ± 0.0%), crude proteins (89.5 ± 1.8%), energy (83.1 ± 1.7%) and fatty acids (85.8 ± 7.5%). The ADCs of the nutrients, energy, DHA and other fatty acids showed that Schizochytrium spp. is a high-quality candidate for fish oil substitution and supplement of LC-PUFA in fish feed with vegetable oils.

An 8-week feeding trial was conducted to examine effects of wheat naturally contaminated with Fusarium mycotoxins (deoxynivalenol, DON 41 mg·kg−1) on growth performance and selected health indices of red tilapia (Oreochromis niloticus × O. mossambicus, initial weight = 4.3 g/fish). Five experimental diets were formulated by replacement of clean wheat with naturally contaminated wheat resulting in graded levels of DON and zearalenone (ZEN) (Diet 1 0.07/0.01, Diet 2 0.31/0.09, Diet 3 0.50/0.21, Diet 4 0.92/0.37 and Diet 5 1.15/0.98 mg·kg−1). Groups of 50 fish were randomly allocated into each of 20 aquaria and fed to near-satiety for eight weeks. Growth rate, feed intake and feed efficiency of fish fed the experimental diets decreased linearly with increasing levels of Fusarium mycotoxins (p &lt, 0.05). Although growth depression was associated with feeding diets naturally contaminated with Fusarium mycotoxins, especially DON, no biochemical and histopathological parameters measured in blood and liver appeared affected by Fusarium mycotoxin concentrations of diets (p &gt, 0.05). Though there was no clear evidence of overt DON toxicity to red tilapia, it is recommended that feed ingredients should be screened for Fusarium mycotoxin contamination to ensure optimal growth performance.