Nutritional Evaluation of Several Protein Sources for Yellowtail (Seriola quinqueradiata)

Nutritional value of brown fish meal (BFM), soy protein concentrate (SPC) and corn gluten meal (CGM) for young yellowtail diets was evaluated by biological and biochemical methods. These proteins were incorporated at 30 - 50% of the diet as the only source of protein. The highest growth, feed efficiency, apparent protein digestibility, PER, NPU and BV were obtained from BFM-fed fish group while the lowest values were CGM-fed fish group, excluding BV which was similar between SPC and CGM. There was no apparent relationship between arginase or citrate synthase activities and protein sources. Blood urea nitrogen (BUN) and RNA concentrations of BFM- and SPC-fed fish groups tended to increase with increasing protein level, but those of CGM-fed fish group remained practically the same. Low protein utilization of SPC and CGM are attributed to their unbalance amino acid profiles and that of CGM is also due to poor digestibility. Among the examined biochemical parameters, BUN may provide useful indication for protein quality evaluation, though clear results were not obtained. At present, NPU and BV are useful parameters because clear growth differences due to dietary nutrition are seen in a rapidly growing fish such as yellowtail

Effect of ration level on non-fecal nitrogen excretion of juvenile yellowtail (Seriola quinqueradiata)

Post-feeding non-fecal nitrogen excretion was determined for juvenile yellowtail in a closed tank system. The highest ammonia excretion value was noticeable 2 hr post-feeding, while the urea excretion rate was highest at 4 hr post-feeding. The ammonia excretion rate of fish fed the lowest ration (1.4%bw) was a half of that of fish fed the highest ration (4.1% bw). The equivalent energy value from ammonia was in the range of 8.7 to 18.0 (KJ/kg bw/day) under present feeding condition

Bioavailability of modified forms of methionine in yellowtail and rainbow trout

Bioavailability of modified methionine products, oligo-L-methionine (OM) and β-1,3-glucan (curdlan) coating methionine was examine by absorbability study in yellowtail (exp-1) and growth study in rainbow trout (exp-2). Effects of feeding frequency on crystaline methionine utilization was also examined in the rainbow trout (exp-2). Plasma free methionine levels increased in yellowtail fed curdlan coating methionine but the levels did not change in OM fed fish. In the feeding study, despite a good absorption of curdlan coating methionine, growth rate of curdlan coating methionine was inferior to crystalline methionine fed group. No growth difference was noted in fish fed a crystalline methionine supplement group either two or four times feeding a day. These results suggested that bioavailability of OM is inferior to curdlan coating methionine. However, the latter product did not give the same growth performance as crystalline methionine