Fish farming is a huge industry in Vietnam, but there is a shortage of protein supplements for fish diets. A potential great source of protein supplement is the co-products of shrimp processing. The present study aimed to investigate the growth performance and haematological parameters of rainbow trout Oncorhynchus mykiss juveniles fed diets containing four different concentrations of shrimp head protein hydrolysates (0% (control), 1, 3 or 5% SHPH, four replicate per treatment). Rainbow trout juveniles were randomly distributed into 12 tanks at a density of 30 fish/tank and were fed twice a day at 8:00 and 17:00 for 8 weeks. Mean weight gain (MWG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER) and survival (SR) were calculated. Significant differences (p<0.05) in MWG, SGR, FCR, PER and SR were detected between treatments, with fish fed 5% SHPH performing the best. Mean white blood cell (WBC), red blood cell (RBC), hemoglobin (Hb) and hematocrit (Hct) significantly increased as dietary protein hydrolysate increased in the diet. Protein and triglyceride concentrations in plasma of were not significantly affected by dietary treatment (p > 0.05). Furthermore, muscle and whole body lipid contents were higher in fish fed 3% and 5% protein hydrolysate from shrimp heads than other groups, but muscle and body protein contents in the group fed 5% were higher than other groups. Results from the present study showed that protein hydrolysate from shrimp heads has good potential for use as protein supplement in rainbow trout diets up to 5%. Supplemental dietary protein hydrolysate from shrimp heads also has potential as an immune enhancer because of an increase in WBC. These data provide a potential use for a current waste product and might serve as a model for other countries that have both warm water crustacean industries and cold water fish industries. Further studies to explore the use of protein hydrolysate from shrimp heads in fish diets at more than 5% are recommended.
Keywords: Growth performance, haematological parameters, Oncorhynchus mykiss, rainbow trout, protein hydrolysate from shrimp head