An 8‐week feeding trial was conducted to determine the quantitative lysine requirement of juvenile grouper Epinephelus coioides (initial mean weight: 15.84 ± 0.23 g, mean ± SD) in eighteen 500‐L indoors flow‐through circular fibreglass tanks provided with sand‐filtered aerated seawater by feeding diets containing six levels of l‐lysine ranging from 19.2 to 39.5 g kg−1 dry diet in 4 g kg−1 increments. The diets, in which 250 g crude protein kg−1 diet came from fish meal and soybean protein concentrate, and 230 g kg−1 from crystalline amino acids, were formulated to simulate the amino acid profile of 480 g kg−1 whole chicken egg protein except for lysine. Each diet was assigned to three tanks in a completely randomized design. Grouper were fed to apparent satiation twice daily during the week and once daily on weekends. Weight gain and specific growth rate increased with increasing levels of dietary lysine up to 27.2 g kg−1 (P < 0.05) and remained nearly the same thereafter (P > 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (P < 0.05) and showed no significant differences among other treatments (P > 0.05). Survival could not be related to dietary treatments. Body composition remained relatively constant except for lipid contents in muscle and liver. Total essential amino acid contents in liver increased with dietary lysine level although there was a slight decline for fish fed the highest lysine level of diet. Plasma protein content increased with increasing dietary lysine level (P < 0.05), but cholesterol, triacylglycerol and glucose contents were more variable and could not be related to dietary treatments. Dietary lysine level significantly influenced morphometrical parameters (condition factor, hepatosomatic index and intraperitoneal fat ratio) of juvenile grouper (P > 0.05). Broken‐line analysis of weight gain indicated the dietary lysine requirement of juvenile grouper to be 28.3 g kg−1 diet or 55.6 g kg−1 dietary protein.

An experiment was conducted to determine the effect of dietary wheat starch on grass carp (Ctenopharyngodon idella) in terms of growth performance, feed efficiency and digestibility. Five isoproteic (23.5%) and isolipidic (5.7%) diets with five supplemented levels of wheat starch (D20, D26, D33, D40 and D47 with 20, 26, 33, 40 and 47%, respectively) were fed to triplicate groups of grass carp (mean initial wet weight 6.9 ± 0.1 g) for 8 weeks. Results showed that weight gain (WG, %), feed efficiency (FE, %) and protein efficiency ratio (PER) in D20, D26 and D33 treatments were significantly higher than those in D40 and D47 treatments (P \ 0.05). Digestibility of carbohydrate and protein was significantly higher in D20, D26 and D33. No significant differences were found in serum glucose and triglyceride contents between treatments. Serum lipase activity of fish fed D40 and D47 was significantly higher than that of fish fed other diets. Wholebody, muscle and liver lipid contents increased with dietary starch level as did mesenteric fat index, hepatosomatic index and viscerosomatic index. In conclusion, when dietary protein level was 23%, the level of dietary wheat starch should maximum be 33% to support normal growth of grass carp. Fish growth was hampered by higher wheat starch ([33%) despite fish ate increasing levels of dietary digestible energy. Furthermore, excess digestible carbohydrate was to some extent converted to lipid that was deposited in various tissues. Most importantly, grass carp could endure high levels of cellulose without any negative effect on growth and digestibilities of dietary protein and carbohydrate.

Problem statement: The utilization of crystalline amino acids was detected for growth performance and body composition of juvenile grass carp (Ctenopharyngodon idella). Approach: L-Lysine sulphate and Methionine Hydroxy Analog-Ca (MHA-Ca) were selected for determination. Two diets were formulated with or without amino acids supplementation. Each diet was assigned to 10 tanks in a completely randomized design for 8 weeks. Results: The results demonstrated that the final weight, Weight Gain (WG) and Protein Retention (PR) of the fish fed diet with supplemental lysine and methionine were significantly higher, while the Feed Conversion Ratio (FCR) were significantly lower in comparison with the reference group. The Condition Factor (CF) of the fish fed diet with lysine and methionine supplementation were significantly higher than the reference group (p<0.05). However, the Viscera Somatic Index (VSI), Hepato Somatic Index (HSI) and Intra Peritoneal Fat Ratio (IPFR) of the tested group were markedly lower (p<0.05). Whole body moisture and muscle protein content of the tested fish significantly increased, while the lipid level of whole body significantly decreased (p<0.05) with the supplementation of lysine and methionine. Conclusion: Results of the present investigation demonstrate significant improvement of growth and feed utilization of grass carp can be achieved by L-Lysine sulphate and MHA-Ca supplementation. WG and PR of the tested group improved 11.4% and 8.3% respectively, while FCR decreased 9.6% in comparison with the reference group (p<0.05)

An 8-week feeding trial was conducted to evaluate the effects of dietary aflatoxin B 1 (AFB 1 ) on growth performance, haematological parameters and histological changes in juvenile Pacific white shrimp, Litopenaeus vannamei. Six practical diets (455 g kg -1 protein, 78 g kg -1 lipid) with different levels of AFB 1 (0, 25, 50, 100, 500, 1000 lg kg À1 ) were formulated. Each diet was fed to triplicate groups of shrimps (initial weight: 0.52 g). The results showed that shrimp fed with control diet (0 lg kg À1 AFB 1 ) had significant higher weight gain (WG) and specific growth rate (SGR) than other groups. However, there were no significant differences in feed efficiency (FE) or hepatosomatic index (HSI) among all groups. Compared to the control diet, AFB 1 supplementation significantly changed the activities of shrimp serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total antioxidant capacity (T-AOC) and glutathione S-transferase (GST) and the content of cholesterol (CHO). Histological damages were identified in the hepatopancreas of shrimp when dietary AFB 1 level was over 107.6 lg kg À1 . Based on this study, it was concluded that the AFB 1 level in Pacific white shrimp diet should be <38.1 lg kg À1 .

A growth trial was conducted to estimate the optimum concentration of dietary magnesium (Mg) for grass carp (Ctenopharyngodon idella). Triplicate groups of grass carp (5.56 ± 0.02 g) were fed diets containing graded levels (187, 331, 473, 637, 779 and 937 mg kg )1 ) of Mg for 8 weeks.Weight gain, specific growth rate and feed efficiency were linearly increased up to 637 mg kg )1 dietary Mg and then levelled off beyond this level. For body composition, dietary Mg levels higher than 473 mg kg )1 significantly decreased the moisture content but increased the lipid content of whole body, muscle and liver. Dietary Mg levels higher than 473 mg kg )1 significantly decreased the ash contents of vertebrae, scales and muscle. Mg contents in whole body, vertebrae, scales and plasma were increased up to 637 mg kg )1 dietary Mg and then levelled off beyond this level. However, Ca and P contents seem to be inversely related to dietary Mg. Dietary Mg levels higher than 473 mg kg )1 significantly decreased Zn and Fe contents in whole body and vertebrae. Broken-line analysis indicated that 687 mg kg )1 dietary Mg was required for maximal tissue Mg storage, as well as satisfied for the optimal growth.