Plant protein-based diets can replace a fish meal-based diet for sustainable growth and body composition of zebrafish

This 3 × 2 factorial study involving three diets at two stocking densities tested the effect of replacing fish meal (FM) with either soybean meal (SBM) or rapeseed meal (RSM) in diets on growth and body composition of zebrafish (Danio rerio). Fish were fed three times daily for eight weeks. Morphometric and water quality parameters were also determined. The survival rate of the fish ranged from 95.2 - 97.8%. The water quality remained within the acceptable limits for tropical aquaculture. The stocking density did not show any significant difference (p>0.05) for the length and weight of the fish. The length, weight and condition factors were significantly higher (p<0.05) in the fish fed FM based diet. The fish length and weight related well (R2) across the diets but this was more significant for RSM than those fed the other two diets. The weight gain (WG), feed conversion ratio (FCR) and protein intake (PI) were significantly higher (p<0.05) in the fish fed the FM based diet than the other diets. No significant differences observed (p>0.05) in the specific growth rate (SGR), food intake (FI) and protein efficiency ratio (PER) among the fish fed the three diets. The crude protein CP, nitrogen-free extract (NFE) and ash contents of these fish did not differ significantly (p>0.05). However, the ether extract (EE) of the fish fed SBM diet was significantly lower (p<0.05 than the other two diets. It appears that both SBM and RSM as sustainable source to partially FM in the diets of zebrafish and similar fish species.

used to analyse the differences in the growth of the fish. Tukey's post-hoc test was used to 224 compare mean to observe significance at p < 0.05.

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The results of the percentage survival of the fish at the end of the experiment are 229 presented in Figure   density for the fish length and weight, though the mean weight and length of fish were 247 numerically higher for the fish stocked at lower stocking density than those stocked at higher  The mean condition factors were 1.2 ± 0.2, 1.15 ± 0.2 and 1.14 ± 0.2 for the fish fed CFM,    The mean values with the same superscript along the same row for diets and the stocking   The multivariate test results show that there were significant differences (p<0.05) in the weight 297 of the fish based on the stocking density. However, there was no significant difference observed 298 among the fish fed the diets. The Mauchly's test revealed no significant differences in the 299 weight of the fish relative to the interaction between the diets and the stocking density.

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The Mauchly's test of sphericity equally revealed significant differences (p<0.05) in the weight 301 of the fish between the first week and the second week of the feeding trial. There were no 302 significant differences; however, in the weight of the fish between the second, and the third 303 week until the fourth week through to the seventh week where significant increments (p<0.05) 304 were observed. Significant differences were manifested in the weight of the fish between the 305 two stocking densities from the fifth weeks to the eight weeks. The difference was due to the 306 reduction in the numbers of the fish due to the fish sampling relative to the respective culture  gained more weight significantly (p<0.05) than the fish in tanks with high stocking density.

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The PI was significantly higher in the fish stocked at high density than those at low density.

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There were no significant differences (p>0.05) in the SGR, FCR, FI, as well as the PER 328 between the two stocking densities among the fish fed the three diets. Fish in tanks with low 329 stocking density converted more food to flesh and gained more weight than those stocked at 330 high density. There were no significant differences between the two stocking densities in the   2.61 ± 0.21 a 1.61 ± 0.09 b 2.51 ± 0.17 a 1.28 ± 0.13 b 2.72 ± 0.14 a 1.37 ± 0.11 b F.Wt (g) 4.94 ± 0.26 a 3.26 ± 0.06 b 3.64 ± 0.21 a 2.31 ± 0.12 b 3.60 ± 0.24 a 2.55 ± 0.16 b Wt.G (g) 2.33 ± 0.05 a 1.65 ± 0.10 b 1.13 ± 0.14 1.03 ± 0.03 0.88 ± 0.01 1.17 ± 0.01 SGR (%) 1.13 ± 0.05 1.25 ± 0.10 0.66 ± 0.08 b 1.04 ± 0.09 a 0.49 ± 0.08 b 1. Values are mean ± standard error. The mean values with the same superscript in the same row The chemical composition of the fish fed the three diets (g/kg DM) 357 The proximate composition of the fish fed the CFM, SBM and RSM based diets are 358 presented in Figure 6. There were no significant differences (p>0.05) in the dry matter (   factor, which is classically considered a health and well-being indicator in fish.

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Accomplishing measurement of fish in fisheries study and biological research is a 390 challenging task but it is a beneficial instrument in determining the size of fish as it grows. species. There was no information on the detailed body composition of zebrafish fed plant 506 protein-based diets compared with the commercial diets used in most zebrafish laboratories; 507 therefore, the results of this study will contribute to this invaluable database for zebrafish nutrition. An aquaculture system using zebrafish for nutrition research needs to develop a 509 method to carry out and elucidate the interactive effect of different nutrient sources on feed 510 digestibility and its effects on the growth and nutrient utilisation of fish. There is a need to