The effect of various processing methods on the physical and biochemical properties of shrimp head meals and their utilization by juvenile Penaeus monodon Fab

Three meals were prepared from Penaeus monodon head waste by drying the raw material in a solar simulator, drying in an oven or blanching the raw material followed by partial de-watering under pressure and air drying. A further three meals were prepared by passing batches of raw or blanched shrimp head waste through a commercial meat/bone separator. The meat fraction was subsequently dried (MBDD) or ensiled. Separated meals contained around 6% less ash, 5% less chitin and 7.5% more protein than unseparated meals but the procedure failed to remove all the exoskeletal material. Separated meals also contained higher levels of astaxanthin and canthaxanthin than solar or oven-dried meals. The highest levels of n−3 polyunsaturated fatty acids (PUFAs) were found in separated meals. However, blanching the raw material prior to processing led to decreased PUFA content, higher free fatty acid levels and significantly higher ( P < 0.05) peroxide values. All the meals were found to be deficient in arginine and methionine plus cystine but separated meals contained greater quantities of the remaining essential amino acids and had essential amino acid indices greater than 0.70. Experimental rations were prepared incorporating either 54% fish meal or 31% of the solar-dried, oven-dried or MBDD shrimp head meals plus sufficient fish meal to generate isoproteinaceous diets. Each diet was fed to triplicate groups of 40, juvenile Penaeus monodon in a 50-day growth trial. Diets containing shrimp head meal performed significantly ( P < 0.05) better in terms of final individual weight, feed conversion ratio and production compared with the 54% fish meal based diet. The diet containing separated shrimp head meal produced the best response, followed by the diets containing oven-dried and solar-dried meal, but the differences were not statistically significant. Similar trends were noted for specific growth rate (SGR) and survival. Tests on the experimental diets indicated that the incorporation of shrimp head meals reduced water stability but increased diet palatability when compared to the fish meal based diet.