Ai Qinghui

Effects of phytase and non-starch polysaccharide enzyme supplementation in diets on growth and digestive enzyme activity for Japanese seabass, Lateolabrax japonicus C.

A feeding experiment was conducted to investigate the effects of dietary exogenous enzymes(Phytase,non-starch polysaccharide enzymes: WX and VP) on growth,body composition and digestive enzymes activitives of Japanese seabass,Lateolabrax japonicus C.(initial weight(6.26±0.10) g).A basal diet was used as the control(Diet 1),which contained 36.1% fish meal and 18.0% compound protein source(soybean meal∶meat and bone meal∶peanut meal∶rapeseed meal=4∶3∶2∶1,and crystalline lysine,methionine and isoleucine were supplemented to simulate the essential amino acid profile of fish meal).Two other diets were supplemented with 200mg phytase and the combination of 800mg WX and 400 mg VP per kilogram diet,respectively.Each diet was fed to triplicate groups of fish in seawater floating cages(1.5m×1.5m×2.0m),and each cage was stocked with 60 fish.Fish were fed twice daily(06:00 and 18:00) to apparent satiation for 8 weeks.The water temperature fluctuated from 27.5℃ to 29.5℃,the salinity from 25‰ to 28‰ and dissolved oxygen content was above 7mg / L during the experimental period.Results showed that exogenous enzymes supplementation did not significantly influence the survival of Japanese seabass(92%—95%),but significantly improved the growth(weight gain(WG) increasing from 859.3% to 947.2% and 905.2%,specific growth rate(SGR) from 4.0 to 4.2 and 4.1%/d)(p0.01).Dietary non-starch polysaccharide enzymes did not significantly affect the carcass moisture,crude protein,crude lipid,ash and gross energy of Japanese seabass.Dietary phytase also had no influence on the carcass moisture,crude lipid and gross energy of Japanese seabass,but significant influence on the carcass crude protein and ash(p0.05).The digestive enzymes activitives in stomach and intestine of fish supplemented with exogenous enzymes showed increasing trend when supplied with exogenous enzymes compared with the control group(Diet 1).The amylase activity of stomach and intestine significantly increasing from 0.05 to 0.16 U/mg and 0.12 to 0.21 U/mg respectively by the supplementation of non-starch polysaccharide enzyme(p0.01),but no significant differences in protease and lipase were observed.Similarly,dietary supplementation of phytase significantly increased the protease activity of stomach and intestine from 0.74 to 1.02 U/mg and 1.09 to 1.71 U/mg respectively(p0.01),but no significant differences in lipase and amylase were observed.

Effects of soybean oligosaccharides on lipid metabolism of Japanese flounder (Paralichthys olivaceus Temminck et Schlegel) fed animal or plant protein source-based diets

A feeding trial was conducted to investigate the effects of dietary soybean oligosaccharides (SBOS) on the levels of cholesterol in plasma and liver, and the fatty acid composition in muscle and liver of juvenile Japanese flounder (Paralichthys olivaceus Temminck et Schlegel). Four isonitrogenous and isocaloric practical diets (crude protein 49%, gross energy 19 kJ/g) including only fish meal (FM) or soy protein isolate (SPI) as sole dietary protein source with (Diets FMO and SPIO) or without (Diets FM and SPI) supplemented SBOS (stachyose, 2.61%; raffinose, 0.61%) were formulated. Each diet was randomly assigned to triplicate aquaria stocked with 30 fish (initial body weight 1.93 ± 0.02 g) each. Fish were maintained in the flow-through aquaria at water temperature ranging from 22.0°C to 25.0°C and fed twice (08:00, 16:00) daily to apparent satiation for 8 weeks. Dietary SBOS supplementation significantly increased the levels of total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) in plasma of the fish fed FM-based diets (P < 0.05), but no significant differences were observed at the levels of plasma triacylglycerol (TG) and low-density lipoprotein cholesterol (LDL-C) and LDL-C/HDL-C ratio (P > 0.05). The levels of TC, TG, HDL-C and LDL-C, and LDL-C/HDL-C ratio in plasma of the fish fed SPI-based diets were not significantly influenced by the supplemented SBOS (P > 0.05). Supplementation of SBOS did not influence the hepatic TC, TG and lipid contents and lipid droplet accumulation in fish fed FM-based diets, but significantly decreased the hepatic TC, TG and lipid contents and lipid droplet accumulation in fish fed SPI-based diets (P < 0.05). In contrast, supplemented SBOS significantly increased fecal cholesterol extraction in the fish fed FM-based diets (P < 0.05), but no significant difference was observed in the fish fed SPI-based diets (P > 0.05). The fatty acid composition in muscle and liver was not significantly affected by supplemental SBOS regardless of dietary protein source (P > 0.05). These results indicate that dietary SBOS supplementation (stachyose, 2.61%; raffinose, 0.61%) does not negatively affect the lipid metabolism of the fish fed FM-based diets, but decrease the incidences of fatty liver of the fish fed SPI-based diets.

Dietary pyridoxine requirement for juvenile cobia (Rachycentron canadum).

Vitamin B6 or pyridoxine in the form of pyridoxal phosphate participates as a prosthetic group of enzymes in a large number of metabolic reactions,particularly those associated with the metabolism of proteins and amino acids. With the success of artificial propagation and larval production,the culture of cobia becomes widely distributed in southern coastal provinces of China(especially in Guangdong and Hainan Provinces) as well as Southeast Asia. However,currently the growth of cobia heavily depends on trash fish and the development of formulated feeds for cobia is still in its infancy. The objective of this study is to detect the optimal requirement of pyridoxine in diet of juvenile cobia Rachycentron canadum.Basal diet was formulated using vitamin-free casein,gelatin and fish protein concentrate as the protein source. The graded levels of PN(0,2,4,8,16 and 32 mg/kg diet) were added to the basal diets to formulate six experimental diets containing 0.22,1.89,3.87,7.54,14.75 and 29.88 mg PN/kg diet,analyzed by HPLC,respectively. Each diet was fed to three replicate groups of cobia in 300 L tanks for 9 weeks,and each tank was stocked with 25 fish [initial weight (3.23±0.06) g]. The water salinity was from 30 to 34,temperature fluctuated from 28 to 32 ℃ and dissolved oxygen was above 7 mg/L. The results showed that specific growth rate(SGR) have an increasing trend with the increase of dietary pyridoxine(from 0.22 to 3.87 mg/kg),but no significant differences were observed among diets containing 3.87 mg/kg PN or above. The contents of PN and AST in liver of fish fed diets with 3.87 mg/kg were significantly higher than the treatments with the contents of PN lower than 3.87 mg/kg,however,there were no significant differences among diets containing 3.87-29.88 mg/kg PN. The contents of PLP and the activities of ALT of the diet containing 7.54 mg/kg PN were significantly higher than the diets containing PN7.54 mg/kg,however,no significant differences were discovered among diets containing PN7.54 mg/kg. The dietary pyridoxine requirement was estimated to be 3.09-3.26 mg/kg by the broken-line model based on the SGR,and the activities of ALT in fish liver.