Growth performance, haematological parameters and proximate composition of rainbow trout Oncorhynchus mykiss fed varying dietary levels of protein hydrolysate from heads of Penaeus monodon shrimp processing industry

Abstract

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% as the control, 1, 3 or 5% SHPH, four replicates per treatment). Rainbow trout juveniles were randomly distributed into 12 tanks at a density of 30 individuals/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 cells (WBC), red blood cells (RBC), hemoglobin content (Hb) and hematocrit (Hct) significantly increased as dietary protein hydrolysate increased in the diet. Protein and triglyceride concentrations in plasma 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.