Glucosinolates (GLS), sinapine (SNP) and crude fiber (CF) are the most limiting antinutrients to including carinata meal (CM) in fish feeds. Manufacturing fish feeds by cook extrusion reduced GLS and SNP concentrations in CM by 48 and 57%, respectively. However, due to the high variation in GLS and SNP in different CM varieties, cook extrusion alone may not be sufficient to reduce GLS and SNP concentrations to tolerable levels by fish, without affecting performance .
In a GLS and SNP tolerance study on hybrid striped bass (HSB) , diets containing ≥ 5.58 µmoles of GLS and 0.54 mg of SNP per gram, resulted in low feed consumption and thus low HSB growth. Therefore, CM ha d to be processed to reduce GLS and SNP concentrations, to enable increas ed CM inclusion levels in fish feeds. CM was subjected to aerobic microbial conversion (AC) followed with a single wash (ACCM) or merely double-washed (W) without AC (WCM). These two processing methods reduced GLS and SNP concentrations in AC CM and WCM by >70 and >83% , respectively . However, CF was increased in ACCM and WCM. Up to 30% of A CCM and 30% of WCM were include d in HSB diets containing similar animal meal contents (20%) and fed for 12 weeks.
Growth increased with increasing processed CM in diets due to improved palatability and increased feed consumption . However, ACCM diets were poorly converted into fish biomass. HSB fed 30% WCM were in better condition and had healthier livers than HSB fed ACCM or the reference diet. Apparent digestibility coefficient (ADC) of protein decreased with increasing ACCM in diets. However, protein ADC of WCM and the reference diet were similar. In a time series study, a ll inclusions of ACCM or WCM increased serum and muscle methionine. High (30%) inclusions of processed CM increased serum tryptophan and valine but reduced serum arginine and leucine. High (30%) inclusions of processed CM increased muscle histidine but reduced muscle leucine and phenylalanine. Only 30% WCM increased muscle lysine and valine. The reference and 30% WCM diets resulted in the highest total essential amino acids (EAAs) in serum but release of total EAAs in serum of HSB fed 30% WCM was elevated continuously over a longer period. High inclusions of ACCM or WCM (30%) in diets resulted in more total EAAs in muscle over a longer period. Muscle EAA to lysine ratios showed that only histidine concentrations were adequate for muscle synthesis over the 36-hour period. Overall, the second wash in WCM improved meal utilization by increasing protein ADC when compared to single-washed ACCM . The specific mechanism(s) associated with process improvements is still under investigation.