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Redclaw (Cherax quadricarinatus) 1 Cherax Endemic to Australia 3 Cherax species : Excellent candidates for commercial aquaculture Redclaw (C. quadricarinatus) Yabby (C. destructor) Marron (C. tenuimanus) Figure 1. Natural distribution of redclaw, yabby and marron (Wingfield, 2008) 2 Cherax Redclaw Yabby Marron 3 Crayfish aquaculture Freshwater crayfish are an ideal aquacultural commodity ● Have excellent flavour and lobster-like appearance - high market value ● No larval stages - no need for expensive sophisticated hatcheries ● Omnivorous, opportunistic feeders - can be fed with inexpensive feeds ● More sustainable than prawn culture - no need for higher stocking densities / expensive coastal sites Female redclaws bearing eggs and juveniles 4 Feed / Feeding The largest operating cost (> 50%) of most fish and crustacean farming Fish meal (FM) and fish oil Expensive Future availability ? (climate change / overexploitation) Research priority Reduction of dependency on FM and fish oil inputs Identification of alternative high-protein and low-cost feed ingredients Feed optimization Require specific nutrient requirement identification Understanding of digestive enzyme activities of target species 5 Cellulose digestion/Endogenous cellulase ECE discovered in commercially cultured decapod crustaceans including freshwater crayfish ECE enables freshwater crayfish to breakdown complex polysaccharides (e.g. cellulose) and utilise plant-derived ingredients Cellulose Cellobiose / cello-oligomers Glucose 6 Crayfish growth studies Previous growth and digestibility studies Protein and lipid digestibility widely assessed Less information on carbohydrates (types/amounts) Effect / potential of soluble cellulose not investigated C. destructor & C. tenuimanus less evaluated 7 Objectives Objectives To investigate the effect of soluble dietary cellulose on growth performance and digestive enzyme activities in 3 Cherax species Growth performance: Feeding trial Enzyme activities: Enzyme assay 8 Methods (I) Feeding trial Table 1. Composition of experimental diets (gkg-1) Ingredient RD TD 581 581 - 200 Diets: Fish meal Reference diet (RD) Corn starch 200 - Fuller’s earth 79 79 Gluten 40 40 Gelatine 50 50 Vitamin/mineral pre-mix 25 25 Fish oil 25 25 Proximate composition % % Dry matter 92.6 92.6 Crude protein 32.9 32.8 Ash 5.0 4.9 Gross energy 17.3 15.8 Test diet (TD) n= 34 Feeding: 3% per day, twice Carboxymethyl cellulose 9 Methods (I) Feeding trial Culture: 12 wk independent trials Table 2. Culture conditions maintained through out the experimental period Species Temp. / oC Cond./µscm-1 pH DO / ppm Redclaw 26.0±0.01 517±4.0 7.9±0.01 7.42±0.05 Marron 20.4±0.03 499±1.0 7.9±0.01 8.67±0.02 Yabby 26.2±0.02 536±5.0 7.9±0.01 7.60±0.02 Outcome: 𝑆𝑆𝑆𝑆𝑆𝑆 = 100 𝑋𝑋 𝑙𝑙𝑙𝑙 (𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤ℎ𝑡𝑡/𝑔𝑔) – 𝑙𝑙𝑙𝑙 (𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤ℎ𝑡𝑡/𝑔𝑔) 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 = 𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 𝑜𝑜𝑜𝑜 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 (𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑) 𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑜𝑜𝑜𝑜 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑎𝑎𝑎𝑎 𝑒𝑒𝑒𝑒𝑒𝑒 𝑋𝑋100 𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑜𝑜𝑜𝑜 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑎𝑎𝑎𝑎 𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 Analysis : Two-way ANOVA 10 Methods Specifications: 36 tanks / 27 L each Recirculating /purifying system Automatic control of pH, temp., CD at a set value Constant water exchange rate at a desired value Aquaculture facility – QUT Pilot Plant Precinct, Banyo, QLD Individual tank unit with cages 11 Methods 12 Methods (II) Enzyme assay Enzymes assayed from the Hepatopancreas Protease Amylase Cellulase Specific enzyme activity (enzyme units (U) per milligram of protein) was calculated Methods As described by Pavasovic et al. (2004) Analysis: Independent “t” test 13 Results (I) Feeding trial Table 3. SGR and Survival rate (%) Species Redclaw Marron Yabby Diet SGR RD TD RD TD RD TD 0.193±0.019a 0.093±0.019b 0.146±0.019a 0.107±0.017a 0.105±0.018a 0.086±0.017a Survival rate (%) Female Male Total 100.0a 88.2a 94.1a 94.1a 64.7a 79.4a 100.0a 94.1a 97.1a 88.2a 94.1a 91.2a 82.4a 100.0a 91.2a 100.0a 64.7b 82.4a [Significance level = p<0.05] Redclaw: SGR of (RD) significantly higher than (TD) Lower survival rates observed in TD than in RD Overall, females showed higher survival rates 14 Results (II) Enzyme assay Table 3. Specific enzyme activity levels (±SEM) in the hepatopancreas. Species Redclaw Marron Yabby Diet Average specific enzyme activity (U/mg of protein) Protease Amylase Cellulase AZO-Casein AZCL-HEAZO-CMCellulose Cellulose (X 10-3) RD 2.469±0.18a 3.731±0.31a 3.408±0.20a 9.690±0.62a TD 1.718±0.23b 2.257±0.30b 2.985±0.33a 7.338±1.12a RD 0.622±0.07a 0.168±0.02a 2.492±0.24a 5.535±0.54a TD 0.315±0.04b 0.079±0.01b 1.540±0.16b 2.203±0.27b RD 1.409±0.11a 2.753±0.21a 1.151±0.08a 4.372±0.38a TD 0.930±0.13b 2.025±0.24b 0.861±0.09b 2.435±0.29b [Significance level = p<0.05] 15 Conclusion/Future studies All three species responded in same direction for experimental diets They appear to utilize starch more efficiently than soluble dietary cellulose Inclusion of 20% soluble cellulose did not appear to have a significant negative effect on individual growth rate in yabby and marron However, digestibility of soluble cellulose is needed to investigate Further testing (lower levels) needed to evaluate potential of soluble cellulose to be used as a feed ingredient in commercial formulated diets Results provide useful information towards formulating low cost crayfish diets for commercial aquaculture 16 Acknowledgment Supervisory team Ridley Agri products, Australia Crayfish suppliers Cherax Park, QLD Aquatic Resource Management Pty Ltd, WA Burns Yabby Farm / Reedy Creek Crays, NSW Technical staff at QUT Family & Friends 17 18