WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2019 61 fish measured. At least three fish were removed from each aquarium and blood samples collected. White blood cell counts and other biochemical tests of health and immunity were measured in collected blood samples. Sampled fish were then macerated, dried to assess moisture content and then stored at -20 C to evaluate protein, lipid and ash content. Remaining fish were maintained on the same feed regimen to be further used in respirometry measurements. This second experiment was performed using a modified flowthrough respirometry setup (Babikian et al. 2017) employing a Strathkelvin 929 6-Channel Dissolved Oxygen System and three RC400 respirometry chambers. At least six respirometry trials per treatment were performed, with one fish per chamber per trial, and the oxygen consumption rate calculated based on dissolved oxygen concentrations entering and leaving the fish chamber, fish body weight and flow rate. The average oxygen consumption rate was then calculated as an estimate of standard metabolic rate of juvenile Nile tilapia. All data were analyzed with SAS software (V 9.2, SAS Institute Inc., Cary, North Carolina, USA) employing one-way ANOVA and Student Newman-Keuls mean separation test and expressed as mean values. Findings All fish survived the trial and thus oil source did not affect survival. Juvenile tilapia offered the diet with soybean oil had a greater final body weight and total length, and consequently lower FCR values, when compared to fish fed diets with industrial hemp oil (no THC) and cannabis oil (with THC) (Fig. 2). No significant differences where observed in length, weight, condition factor or FCR between the two cannabis treatments. Hematology and proximate body composition analyses indicated no significant differences in fish among all dietary treatments. However, fish fed the diet with THC had significantly greater mean respiration rate and, hence, greater metabolic rate, when compared to the fish fed soybean-oil diet (control, Fig. 3). These results suggest an increase rather than decrease in metabolism of Nile tilapia juveniles when offered dietary THC, with reduction in growth and increase in FCR, all of which are undesirable outcomes for farmers. Furthermore, we did not observe any improvement in immune function of the blood of fish offered cannabis. TABLE 1. Ingredients and chemical composition of the three diets offered to juvenile Nilet tilapia over eight weeks. Ingredients are reported on a dry weight basis. Diet 1 Diet 2 Diet 3 Control Industrial hemp Cannabis extract Menhaden fishmeal1 300.0 300.0 300.0 Soybean meal solvent extracted2 418.0 418.0 418.0 Soybean oil 21.3 0.0 10.7 Industrial hemp3 0.0 21.3 0.0 Cannabis extract4 0.0 0.0 10.7 Wheat flour 224.7 224.7 224.7 Vitamin and mineral premix5 20.0 20.0 20.0 Choline chloride 5.0 5.0 5.0 Stay C 2506 1.0 1.0 1.0 Gelatin7 10.0 10.0 10.0 Chemical Composition8 (g/100 g dry matter) Crude protein 41.0 41.0 41.0 Crude lipid 5.50 5.51 5.51 Digestible energy 404.5 404.5 404.5 Phosphorus 1.23 1.23 1.23 1 FF Skagen Denmark. Havnevagtvej 12.9990 Skagen. 2 De-hulled solvent extracted soybean meal, Southern Sates Cooperative Inc., Richmond VA, USA. 3 Industrial Hemp planted under license by Dr. M. Farran and extracted by cold press of seeds. 4 Ether extracted from police-confiscated cannabis. 5 The vitamin and mineral premix provided the following per kg of experimental diet: vitamin A retinyl acetate 1 million IU, vitamin D3 cholecalciferol 0.1 million IU, vitamin E alphatocopherol acetate 7 g, vitamin K 0.5 g, folic acid niacin 0. 1 g, niacin 4 g, calcium pantothenate 2.5 g, riboflavin (B2) 0.6 g, vitamin B12 0.001 g, thiamine (B1 nitrate) 0.5 g, pyridoxine (B6 HCl) 0.5 g, biotin 0.0125 g, vitamin C (ascorbic acid) 0.25 g, inositol 5 g, selenium (as sodium selenite) 0.0045 g, iodine (as calcium iodate) 0.25 g, iron (as sulphate monohydrate) 2 g, zinc (as oxide) 5 g, copper (as sulphate pentahydrate) 0.25 g, manganese (as sulphate monohydrate) 3.5 g, chlorine chloride 75, phosphorus (as monodicalcium phosphate) 2.5, sodium chloride (salt) 225 g, and cellulose 75 g. Calcium carbonate carrier to balance. 6 250 mg kg — 1 active vit C supplied by Stay C®, (L-ascorbyl-2-polyphosphate 25 percent Active C), Roche Vitamins Inc., Parsippany, New Jersey, USA. 7 Himedia laboratories Pvt. Ltd., 23, Vadhani Ind. Est., LBS Marg, Mumbai, India. 8 Based on a calculated value. (CONTINUED ON PAGE 62)
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