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An 8-week feeding trial was conducted to investigate the effects of dietary soy protein concentrate (SPC) levels on growth, blood biochemical indexes, non-specific immune enzyme activity, and nutrient apparent digestibility for juvenile Litopenaeus vannamei (initial weight 0.44 ± 0.002 g). They were formulated by replacing 0% (the control), 10%, 20%, 30%, 40%, 60%, and 80% of fish meal (FM) protein with SPC (designed FM, S11, S22, S33, S44, S55, and S66, respectively). With the replacement level of SPC in the diet was higher than 30%, weight gain (WG) and specific growth rate (SGR) for juvenile Litopenaeus vannamei significantly decreased (P < 0.05) with SPC increasing, but feed conversion ratio (FCR) significantly increased (P < 0.05). When the replacement level was above 40%, the protein efficiency ratio (PER), survival rate (SR), apparent digestibility of dry matter, and energy significantly decreased (P < 0.05). On the contrary, the content of triglyceride glucose (TG) in serum was increased significantly (P < 0.05). Apparent digestibility for crude protein and total lipid were significantly higher at higher fishmeal inclusion (0 and 10% SPC replacement) and significantly lower at lower fishmeal inclusion (< 70%) (P < 0.05). In conclusion, with reference to all the parameters, SPC can be used to replace up to 30% of fishmeal protein in shrimp feeds and so the total fishmeal exceeds 70% be used to cater to shrimps' dietary needs. [ABSTRACT FROM AUTHOR]

A 10-week feeding trial was conducted to investigate the effects of dietary carbohydrate-to-lipid (CHO:L) ratios on glycogen content, hematological indices, liver, and intestinal enzyme activity of sub-adult grouper Epinephelus coioides. Five iso-nitrogenous (496.0 g kg−1 protein) and iso-energetic (21.6 KJ g−1 gross energy) diets with varying CHO: L ratios of 0.65 (D1), 1.31 (D2), 2.33 (D3), 4.24 (D4), and 8.51 (D5), respectively, were fed to triplicate groups of 20 fish (average 275.1 ± 1.86 g). Results showed that the weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) of sub-adult grouper increased and then stable when dietary CHO:L ratios reach D4 (CHO:L = 4.24). The trend of feed conversion ratio (FCR) was opposite to PER. Along with the dietary CHO:L ratios, the liver and muscle glycogen level increased gradually. Plasma triglycerides (TG) and glucose (GLU) were all maximized at D5 (CHO:L = 8.51) group, cholesterol (CHOL) at D4 (CHO:L = 4.24) group. Digestive enzyme activities were significantly affected by dietary CHO:L ratios. Liver hexokinase (HK), alkaline phosphatase (AKP), and glucose-6-phosphate dehydrogenase (G6PDH) activity increased significantly as CHO:L ratios increased. Liver lysozyme (LYZ) and superoxide dismutase (SOD) activity of sub-adult grouper fed the D4 diet was significantly higher than that of the D2 (CHO:L = 1.31) diet. The trend of acid phosphatase (ACP) is opposite to AKP. The regression model analysis showed that the most suitable dietary CHO:L ratio to reach the highest SGR is 6.06. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate the dynamic process of soybean β-conglycinin in digestion, absorption, and metabolism in the intestine of grass carp (Ctenopharyngodon idella). Fish fed with 80 g β-conglycinin/kg diet for 7 weeks, the intestinal digestive enzyme was extracted to hydrolyze β-conglycinin in vitro, the free amino acid and its metabolism product contents in intestinal segments were analyzed. The present study first found that β-conglycinin cannot be thoroughly digested by fish intestine digestive enzyme and produces new products (about 60- and 55-kDa polypeptides). The indigestible β-conglycinin further caused the free amino acid imbalance, especially caused free essential amino acid deficiency in the proximal intestine but excess in the distal intestine. Moreover, these results might be partly associated with the effect of β-conglycinin in amino acid transporters and tight junction-regulated paracellular pathway. Finally, dietary β-conglycinin increased the content of amino acid catabolism by-product ammonia while decreased the amino acid anabolism product carnosine content in the proximal intestine and distal intestine. Thus, the current study first and systemically explored the dynamic process of β-conglycinin in digestion, absorption, and metabolism, which further supported our previous study that dietary β-conglycinin suppressed fish growth and caused intestine injure. [ABSTRACT FROM AUTHOR]