Egg hatching rate and fatty acid composition of Acartia bilobata (Calanoida,Copepoda) across cold storage durations

To investigate egg storage capacity of the copepod Acartia bilobata for aquaculture interest, we tested hatching success rate (HSR) of inclusive eggs (mixture of all egg types) after 4°C storage. The HSR peaked after 14 days storage when incubating at 28°C for 48 hr (85.8 ± 1.6%) and 72 hr (87.6 ± 0.9%), then gradually declined until 1 year (48 hr: 7 ± 0.6%; 72 hr: 19.4 ± 3.9%). Reallocation of fatty acid profile suggests that docosahexaenoic acid (DHA) is correlated with the HSR of A. bilobata eggs. Additionally, we investigated the HSR of diapausing eggs (unhatched eggs after 72 hr incubation of the inclusive eggs) after 4°C storage. Their HSR peaked after 14 days storage (48 hr:75.3 ± 3.5%; 72 hr:78.2 ± 2.1%), then gradually declined until 60 days (48 hr HSR:42.1 ± 2.3%; 72 hr HSR:53.0 ± 3.2%). Overall, we illustrated the hatchability of diapausing and quiescent eggs of A. bilobata after 4°C storage. The cold storage capacities were low (<60% HSR after 60 days), and it could be limited by the egg DHA content. Our findings provide implications for future studies aiming to improve cold storage techniques of tropical copepod eggs for aquaculture applications.     

Soybean meal and wheat flour,proper dietary protein sources for optimal growth of snail (<Emphasis Type="Italic">Semisulcospira coreana</Emphasis>)

A 10-week feeding experiment was conducted to determine the proper dietary protein source for optimal growth performance of juvenile snails, Semisulcospira coreana. Sixteen isonitrogenous (31% crude protein) and isocaloric (4.2 kcal/g DM) experimental diets (designated as FM, F-FM, SBM, F-SBM, WF, F-WF, SSM, F-SSM, SCR, F-SCR, UP, F-UP, FWP, F-FWP, MIX and F-MIX) were formulated to contain 41% fish meal, 42% fermented fish meal, 59% soybean meal, 55% fermented soybean meal, 55% wheat flour with 26% fish meal, 55% fermented wheat flour with 29% fish meal, 50% sesame seed meal with 10% fish meal, 50% fermented sesame seed meal with 11% fish meal, 55% soya-curd residue or fermented soya curd residue with 25% fish meal, 50% Undaria powder or fermented Undaria powder with 24% fish meal, 50% freshwater plant with 29% fish meal, 50% fermented freshwater plant with 28% fish meal, a mixture of 8% soybean meal, 10% wheat flour, 8% sesame seed meal, 8% soya-curd residue, 8% Undaria powder and 8% freshwater plant with 17% fish meal, and 50% the fermented mixture with 16% fish meal, respectively, as dietary protein sources. Juvenile snails (average weight, 32 ± 0.7 mg) were randomly distributed in forty-eight 25-L aquaria (16 L water each) in a flow-through system at a density of 130 snails per aquarium. Three replicate groups of snails were fed one of the experimental diets ad libitum once per day for 10 weeks. At the end of the feeding experiment, survival of snails was above 98% and not significantly different among the dietary treatments. The best final body weight was observed in snails fed the SBM and WF diets. There were no significant differences in final body weight of snails fed the F-SBM, WF, F-WF and MIX diets, but the value was higher than that of snails fed the FM, F-FM, FWP and F-FWP diets. The lowest value was observed in snails fed the SSM, F-SSM, SCR and F-SCR diets. Whole body protein and lipid contents of snails varied with dietary protein sources. Amino acid composition of whole body was altered by dietary protein sources. The results of the present study indicate that dietary protein sources significantly influence proximate and amino acid composition, and growth performance of snails. Fermentation with ferminpan instant brown yeast does not improve nutritional quality of the protein sources, and soybean meal and wheat flour in combination with fish meal could be potential protein sources in feeds for juvenile snails.     

Determining Wheat Dough Mixing Characteristics from Power Consumption Profile of a Conventional Mixer

A Hobart mixer with a pin‐type attachment was used to mix soft wheat flour dough. Power consumption profiles were measured continuously during mixing for 20 min using a current transducer and a data logging system. Experimental variables were quantity of flour (500, 1,000, and 1,500 g of dry wheat flour), water content (43, 45, and 47%, wb), and mixer speed setting (low, medium, and high). The power consumption profiles were evaluated by moving average and spectral analysis. Peaks in the power consumption profiles were located to determine the optimal mixing time. The optimal mixing times were then compared with storage and viscous moduli measured using a dynamic rheometer to assure the maximum strength of wheat dough at the optimal mixing time. Tolerance was determined using the signal amplitude and phase angle data from spectral analysis. Optimal mixing times of various doughs at medium speed ranged from 510 to 850 sec; low and high flour quantities required longer mixing times than medium quantity of flour. The optimal mixing time increased when the moisture content was lowered. Tolerance was affected by mixing speed and moisture content of flour