The efficacy of a single cell protein (SCP) methanotroph (Methylococcus capsulatus, Bath) bacteria meal (FeedKind®, Calysta, Menlo Park, CA, United States), in Pacific white shrimp (Penaeus vannamei) diets was studied to determine growth performance, survival rate and disease resistance against Vibrio parahaemolyticus causing Acute Hepatopancreatic Necrosis Disease (AHPND). The growth trial was assigned in a completely randomized design (CRD) with four treatments and 5 replicates of each, T1: a fishmeal-based control containing 15% fish meal and 3 diets with graded levels of methanotroph bacteria meal, namely T2: 5% methanotroph bacteria meal, T3: 10% methanotroph bacteria meal, and T4: 15% methanotroph bacteria meal. Shrimp were fed ad libitum for 6 weeks on trial diets to assess growth. Subsequent to the growth trial, three replicates of the same groups were exposed to V. parahaemolyticus by a single bath challenge and held for a further 15 days on the same diets as the growth study to assess survival and resistance. No significant differences (p > 0.05) in survival or in growth performance, including final weight, weight gain, specific growth rate, feed consumption or feed conversion ratio of white shrimp fed feeds containing methanotroph bacteria meal or control diets for 6 weeks. Immune markers such as hemocyte counts, phenoloxidase, superoxide dismutase and lysozyme activity were similar across all groups after the 6-week feeding trial. In a V. parahaemolyticus challenge, methanotroph bacteria meal in the diet significantly promoted the survival rate, and the reduction of Vibrio sp. in the hepatopancreas of white shrimp. Hemocyte count and phenoloxidase activity showed no significant differences (p > 0.05) between diet treatment groups, but hemolymph protein was significantly higher (p < 0.05) in shrimp fed diets containing 15% methanotroph bacteria meal after challenge. The Vibrio colony counts from hepatopancreas in the treatment groups were all significantly lower than the control (p < 0.05). The findings show that methanotroph bacteria meal can entirely replace fishmeal in white shrimp diets and the 15% inclusion of methanotroph bacteria meal in shrimp diet shows no adverse effects on growth performance, feed utilization and survival rate. In addition, shrimp fed methanotroph bacteria meal diets exhibited improved survival rates to an AHPND challenge.

Zinc is an essential trace mineral to fish and vital to various biological processes and function. The artificial diets offered to intensively cultivated fish must possess the zinc content required by the animal metabolism for health maintenance and high weight gain. However, essential elements must also be in an available form to be utilized by the organism. Thus, this study was designed to evaluate the effects of different zinc forms, including organic zinc (zinc amino acid complex) and inorganic zinc (zinc sulfate) as feed additives in diets on in vitro protein digestibility, growth performance, feed utilization, digestive enzyme activity, immune response and muscle quality of Asian seabass (Lates calcarifer). The study was assigned in CRD with 3 treatments and 3 replicates. Three groups of fish with mean weight 22.54 ± 0.80 g, were given a basal diet either unsupplemented (control) or supplemented with 50 mg Zn kg −1 , as zinc sulfate (ZnSO 4) or zinc amino acid complex (ZnAA). The fish were fed experimental diets 3.0% of their body weight per day, twice daily at 08.00 and 16.00 h, for 10 weeks. At the end of the experiment, no significant differences were observed on protein digestibility, survival, growth performance and feed utilization across the three dietary treatments (P>0.05). Fish fed ZnSO 4 diets exhibited a significant increase in the specific activities of total protease, pepsin and trypsin compared with ZnAA and the control (P<0.05). Hematocrit, lysozyme and superoxide dismutase activities of fish fed ZnAA diets were significantly higher compared with all other groups (P<0.05). However, no significant differences were observed for muscle quality and whole body composition (P>0.05). The results of the present work allowed us to conclude that there was no difference in the growth between the two zinc sources but ZnAA supplementation exhibited a higher immunity response in Asian seabass.

The characteristics of digestive enzyme from red bee shrimp (Caridina Cantonensis), a tiny ornamental shrimp, were investigated under various pH ranging from 2 to 12. The aim of this study was to find out the specific activities of protease, amylase, lipase, cellulose, trypsin and chymotrypsin and in vitro raw materials by shrimp enzyme digestibility. Fifteen and sixty-day old shrimp were obtained from private farms in Bangkok, Thailand. Protease, lipase, amylase, cellulase, trypsin and chymotrypsin specific activity were determined. The results showed that protease activity had its optimal activity at pH ranging from 8 to 10 and showed the highest activity at pH 10 in both age groups. The alkaline amylase activities were found to be significantly higher than acidic amylase in both age groups. Both acidic and alkaline amylase activity of the 15-day old shrimp was significantly lower than the larger shrimp. The Lipase activity in the 60-day old shrimp showed the highest activity at pH 12, pH 10 and 11, respectively. In the 15-day old shrimp, the lipase activity was stable over a broad pH ranging from 2-12. In the 60-day old shrimp, the cellulase activity showed the highest activity at assay condition pH 7 and decreased when pH levels increased. In the 15-day old shrimp, cellulase activity showed optimal pH at pH 8 and 11. The trypsin and chymotrypsin activity at neutral to weak alkaline condition was greater under acidic condition in both age groups. The activity of 15-day old shrimp was significantly lower than the older shrimp. Regarding in vitro digestibility, the study on protein digestion showed that fish meal was suitable to be a protein source for red bee shrimp. The carbohydrate digestibility showed that wheat flour and maltodextrin were more appropriate as a carbohydrate source for red bee shrimp than cassava, rice bran and Na-alginate. Therefore, it can be concluded that red bee shrimp had diet digestibility in neutral to mid alkaline condition. The animal protein materials are appropriate to be red bee shrimp feed ingredients with low fiber and carbohydrate source.

The issue of low fishmeal diets has been a hot-button topic in the animal industry, including the aquafeed industry, for the past thirty years due to insufficient fishmeal production and unsustainable fishery. Reducing fishmeal in diets that may lack some essential minerals, especially trace minerals such as zinc, copper, manganese, and selenium, will affect animal performance. Hence, several trace mineral concentrations in the diets of Litopenaeus vannamei were studied. The trial was assigned through a completely randomized design with 3 treatments and 10 replicates. The diets with 37% crude protein were formulated and topped up with different trace mineral levels of 1x, 2x, and 3x. All diets were fed to the shrimps for 4 weeks and the results showed no significant differences (P>0.05) on all growth performance parameters. The numerical values of growth performance, however, showed an improving trend when mineral concentrations were increased. Immune responses, such as phenoloxidase activity and glutathione, showed no significant difference between treatments (P>0.05), but the phenoloxidase activity showed an increase in numerical value when the mineral concentrations were higher. Therefore, the results showed that an increase of trace mineral concentrations in the diets of the Pacific white shrimp showed a promotion of growth performance and improvements in the immune responses.

How to cite this article: Burri L, Berge K, Chumkam S, Jintasataporn O. Effects of different feed inclusion levels of krill meal on growth and hepatopancreas morphology of