De‐oiled (<10 g/kg oil) carinata (Brassica carinata) meal is high (>400 g/kg) in protein, but its use in fish diets will likely be limited mainly by glucosinolates (GLS), sinapine and crude fibre. Two feeding experiments were conducted to determine the response of hybrid striped bass (Morone chrysops ♀ X M. saxatilis ♂, HSB) to inclusion of cold‐pressed carinata meal (CPCM) in diets. Cook extrusion reduced an average of 44% and 57% of GLS and sinapine concentrations in diets, respectively. In experiment 1, diets containing 0.71–2.71 μmoles of GLS and 0.034–0.181 mg of sinapine/g did not significantly (p > .05) reduce feed consumption, utilization or growth, resulting in similar concentrations of thyroxines and consequently no effect on deiodinase enzymes. In experiment 2, there was a significantly reduced (p < .05) feed consumption in fish fed diets containing 5.58–9.52 μmoles of GLS and 0.54–0.75 mg of sinapine/g, resulting in HSB exhibiting lethargic swimming and feeding behaviours, and consequently poor feed utilization and growth. Cook extrusion reduced about half of GLS and sinapine, and HSB tolerated ≤2.71 μmoles of GLS and ≤0.31 mg of sinapine/g of diet without affecting feed consumption and utilization, growth and thyroid metabolism.

A 56‐day growth trial was conducted to determine the amount of fish meal (FM) in rainbow trout (Oncorhynchus mykiss) diets containing 200 g/kg FM as the sole animal protein source; that could be replaced with carinata (Brassica carinata) meal (CM) processed by aerobic conversion (AC, by fungi ssp.) followed by a single wash (ACCM). ACCM replaced 50, 100 and 150 g of FM. Replacement of ≥100 g of FM with ACCM, resulted in reduced (p < 0.01) growth, due to reduced dietary lysine and diet consumption (p < 0.01). Fulton's condition factor K decreased (p < 0.01) with increased FM replacement. FCR (p < 0.01) had an inverse relationship with diet consumption. The trend in FCR was similar to the trend in PER (p < 0.01). Apparent net protein utilization was lower (p < 0.01) for the highest FM replacement diet. There was no effect of FM replacement by ACCM on whole‐body composition or viscera, spleen and liver weights. However, visceral fat increased (p < 0.01) with increased feed consumption. There was no apparent effect of ACCM on hematocrit, haemoglobin or mean corpuscular haemoglobin contents. Results of this study indicate that replacement of ≥100 g of FM by ACCM in low FM/animal (200 g/kg) RBT diets may have been achieved if feed consumption and dietary lysine were similar.

Replacement of >25% of fish meal (FM) with aerobically converted carinata meal (ACCM) in low (200g/kg) animal protein (reference = 200g/kg FM) diets of rainbow trout Oncorhynchus mykiss resulted in reduced growth, partly due to reduced feed consumption and protein utilization. In this study, we determined the effect of FM replacement with ACCM on trypsin activity, apparent digestibility coefficients (ADCs) of protein, and essential amino acid (EAA) or conditionally essential amino acid (CEAA) ADCs and bioavailability. Replacement of FM did not alter protein ADCs or trypsin activity. Replacement of >25% FM reduced all EAA and CEAA ADCs except for arginine and leucine which were only reduced by 75% FM replacement. Only serum free lysine and muscle free histidine were reduced by >25% FM replacement. Muscle free lysine was only reduced by 75% FM replacement. Replacement of FM reduced EAA peak concentrations and resulted in slower release of EAAs in serum. Cumulative total EAAs in serum and muscle decreased with FM replacement. Ratios of EAAs to lysine showed that tryptophan was the most limiting EAA. However, isoleucine, leucine, methionine and phenylalanine were also inadequate for muscle synthesis for the first 9–12 hr following force‐feeding. Optimal time for protein synthesis was ≥36 hr. Although any level of FM replacement did not reduce protein ADCs and trypsin activity, replacement of ≥25% FM reduced EAA ADCs and bioavailability of lysine and histidine, which partly contributed to the observed differences in growth.

No abstract

Leaf meals are potential alternatives to soybean meal (SBM) in fish diets in developing countries because they are cheaper. Moringa oleifera (MOR) and Leucaena leucocephala (LEU) reduced nutrient digestibility of diets compared with SBM in an earlier study. However, fish raised outdoors consume natural foods, which might offset the negative effects of leaf‐meal diets. We conducted a feeding trial using mixed‐sex Nile tilapia (5.2 g) to assess performance of fish fed 36% protein diets with different concentrations of MOR and LEU leaf meals in place of SBM. Fish in static pools were fed daily to apparent satiation for 59 d. Individual weight gain (30.4–34.7 g), survival (91.8–97.3%), feed conversion ratio (FCR, 1.6–1.9), proximate composition, plasma lysozyme activity, and intestinal proteolytic enzyme activity were similar among diets. However, fish fed diets containing leaf meals had higher concentrations of n‐3 fatty acids than those fed the SBM control. Despite lower nutrient availability of the leaf‐meal diets compared with the soy diet, MOR or LEU could replace up to 30% of the SBM protein without reducing fish performance. Inclusion of poultry meal in the diets and probable nutrient supplementation from natural foods appeared to compensate for the lower nutritional value of the leaf meals compared with SBM.