Nutritional and immunological studies of red seabream (Pagrus major) and Pacific white shrimp (Litopenaeus vannamei) fed marine protein hydrolysates

Abstract

The studies presented in this dissertation are aimed to evaluate supplementary effects of marine protein hydrolysates in low fish meal diets on growth performance, feed utilization, innate immunity, hematological parameters, diet digestibility, gut morphology and disease resistance of red seabream (Pagrus major) or Pacific white shrimp (Litopenaeus vannamei). Chapter two was conducted to evaluate the effects of salmon protein hydrolysate (SalH), tilapia protein hydrolysate (TH) and tuna protein hydrolysate (TuH) supplemented low fish meal diet in red seabream diets. Two experimental diets were prepared as a high fish meal diet (HFM) to contain 36.8% fish meal (FM) and a low-FM diet (LFM) to contain 13.5% FM. Two other experimental diets were prepared by dietary inclusion of SalH and TH to LFM based diet at 5% inclusion level. One other diet was prepared by coating 2% TuH to LFM diet (designated as, SalH, TH and TuH respectively). Growth performance and feed utilization were significantly higher in fish fed HFM or protein hydrolysate diets compared to LFM group. Feed intake was significantly higher in fish fed HFM and TuH diets. Dry matter and protein digestibility were significantly higher in HFM, SalH and TH diets than the LFM diet. Innate immune responses of red sea bream were significantly improved by dietary supplementation of hydrolysates. Intestine morphological parameters were positively influenced by HFM, SalH, TH and TuH diets. Relative expression levels of liver IGF-1 mRNA was significantly higher in fish fed HFM, and protein hydrolysate diets. Survival rates were higher in HFM and hydrolysate groups than the LFM group after Edwardsiella tarda challenge. Therefore, these results indicate that reduced feed utilization and immune responses of red seabream by LFM diet can be recovered by supplementing marine protein hydrolysates. In chapter three, supplemental effects of TH and/or shrimp hydrolysates (SH) were evaluated in red seabream diet. The HFM diet contained 37% FM and the LFM diet contained 18.5% FM. Three other experimental diets were prepared by dietary inclusion of TH, mixture of TH and SH or SH in low FM based diet at 5% inclusion level (designated as TH, TH/SH and SH). Growth and feed utilization of fish fed SH diet were significantly higher compared to HFM and LFM diet. Protein digestibility of fish fed SH was significant compared to the other dietary treatmentInnate immune responses and intestine morphometric parameters of red seabream were significantly improved by dietary supplementation of SH and/or TH. The highest survival rate was observed in the SH group against Edwardsiella tarda. Therefore, these results indicate that dietary SH and/or TH supplemented LFM diet, which contains 18.5% FM, can improve the performance of red seabreams better than a HFM diet which contains 37% FM. Chapter four was conducted to examine the effects of SH or krill meal (KM) in a LFM diet for red seabream compared to a LFM and HFM diets. The HFM diet contained 40% FM and the LFM diet contained 25% FM. Two other experimental diets (SH and KM) were prepared by dietary inclusion of SH and KM in LFM diet at 5% inclusion levels in exchange of 12.5% FM from the LFM diet. Growth and feed utilization were significantly improved in fish fed HFM, KM and SH supplemented diet compared to LFM group. Interestingly, these parameters of fish fed SH diet were significantly higher than KM and HFM groups. Protein digestibility of SH diet was significantly higher than KM, HFM and LFM diets. DM digestibility of SH diet was comparable to HFM diet and significant than KM and LFM diets. Innate immune responses of fish fed SH diet were significantly enhanced compared to the LFM group. Hemoglobin level of fish fed SH and KM diets were significant to LFM group. Liver IGF-1 mRNA expression of SH diet fed fish group was comparable to HFM group. Therefore, Compared to KM, SH can be used to replace FM from red seabream diet down to 20% and fish performance can be maintained better than a 40% FM containing diet. In chapter five, effects of TuH, SH, and DFS were examined on growth, feed utilization, intestinal morphology, innate immunity and disease resistance of Pacific white shrimp. A diet containing 4.49% of squid liver powder (SLP) was regarded as the control diet and three other diets were prepared by supplementing TuH, SH and DFS (designated as SLP, TuH, SH and DFS). Growth and feed utilization of shrimp were significantly improved by the SH diet. Innate immune responses of shrimp were enhanced by dietary SH supplementation. Shrimp fed the TuH, SH and DFS diets exhibited significantly higher lipid composition than SLP group. SH diet showed significantly higher dry matter digestibility than TuH, and DFS diets. Protein digestibility was significantly higher in SH diet compared to the other diets. Therefore, the performance of Pacific white shrimp can be effectively improved by dietary shrimp hydrolysates compared to SLP. In chapter six, effects of different dietary levels of DFS, SH and TuH (2% or 4% DFS, 1% or 2% SH and 1.5% or 3% TuH) were evaluated in diets for Pacific white shrimp compared to a diet containing squid liver powder (designated as SLP, DFS-2, DFS-4, SH-1, SH-2, TuH-1.5 and TuH-3). Final body weight of shrimp fed SLP diet was significantly lower compared to other diets. Weight gain and protein efficiency ratio of shrimp were significantly improved by DFS-4, SH-1 and TuH-1.5 diets. Innate immune response parameters of shrimp were significantly improved by hydrolysate supplementation regardless of inclusion level. Hemolymph THC was significantly higher in SH-2, TuH-1.5 and TuH-3 groups compared to SLP group. Hyaline cell count was significantly lower in shrimp fed SLP diet. Protein digestibility was significantly higher in diets containing hydrolysates. Dry matter digestibility was significantly higher in DFS-2, SH-1, TuH-1.5 and TuH-3 diets compared to SLP diet. Disease resistance against Vibrio harveyi was significantly affected by DFS, SH and TuH diets. In conclusion, dietary supplementation of SH and TuH in these levels seems to improve growth and immunity of Pacific white shrimp among tested diets.