Studies Of Arginine Requirement For Juvenile Hybrid Sturgeon(Acipenser Schrenckii♀×Acipenser Baeri♂)

This experiment was aimed to study the dietary arginine requirement of juvenile hybrid sturgeon(Acipenser schrenckii♀×Acipenser baeri♂). Seven isonitrogenous and isolipidic diets were formulated to contain graded dietary arginine levels ranging from 1.74% to 3.54%(dry matter) in approximately 0.3% increments, and dietary actual arginine levels was 1.76%, 2.05%, 2.36%, 2.05%, 2.93%, 3.24% and 3.53%,respectively. The experiment fish was purchased from Beijing Fangshan breeding center.The experiment was carried out in indoor aquarium with controlled water circulation system. Before the experiment, the fish were acclimatized two weeks. After the domestication, a total of 630 juvenile hybrid sturgeons with an average initial body weight of(3.63±0.08) g were randomly divided into 7 groups with 3 replicates per group and 30 fish per replicate. During the experiment, the water temperature controlled in 22±1℃, and dissolved oxygen is greater than 5 mg/L, and keep in the natural light.The fish was fed 4 times a day by hand to apparent satiation at 7:00, 11:00, 16:00 and19:00. At the same time, recording the amount of feeding, regularly change water,disinfection, to ensure good water quality. The experiment was lasted for 8 weeks. The results showed as follows:(1) The specific growth rate, weight gain, feed efficiency ratio, protein efficiency ratio and condition factor were significantly increased(P<0.05), and the maximum value appeared in 2.64% group except condition factor appeared in 2.93% group. The value of that indices were no significant differences with dietary arginine supplementation(P>0.05). The dietary arginine levels had no significant effect on theviscerosomatic index(P>0.05). The content of crude protein in whole body on 2.64%and 2.93% group were significantly increased(P<0.05), compared to the 1.76% group.There were no significant differences in moisture, crude lipid and ash of whole body(P>0.05).(2) The content of whole body total amino acids and non-essential amino acids were significantly increased with dietary arginine supplementation(P<0.05), and the maximum value appeared in 2.64% group. Compared to the 1.76% group, the content of lysine on 3.24% and 3.53% group were significantly decreased(P<0.05), the content of aspartic acid on 2.36% and 2.64% group were significantly increased(P<0.05), the content of glutamic acid on 2.64% group was significantly increased(P<0.05), the content of proline on 2.64% and 2.93% group were significantly increased(P<0.05).(3) Compared to the 1.76% group, the activity of serum glutamic-oxalacetic transaminase was decreased(P<0.05), and the content of serum total protein and albumin were increased significantly on 2.64% group(P<0.05). The content of serum urea nitrogen was decreased and serum glucose was increased significantly on 2.64%and 2.93% group(P<0.05). The content of serum triglyceride on 2.36%, 2.64%, 2.93%and 3.24% group were significantly decreased(P<0.05). Dietary arginine levels had no significant effect on the activity of glutamic-pyruvic transaminase and the content of globulin and cholesterin in serum(P>0.05).(4) Compared to the 1.76% group, 2.64% and 2.93% group significantly increased the activity of superoxide dismutase(SOD) and reduced glutathione(GSH) in intestine(P<0.05), and significantly decreased the activity of malonaldehyde(MDA) in midgut of juvenile hybrid sturgeon(P<0.05). The dietary arginine levels had no significant effect on the activity of MDA in foregut and hindgut(P>0.05). Dietary arginine levels had no significant effect on the activity of MDA and SOD in serum and liver(P>0.05).(5) Compared to the 1.76% group, 2.64% and 2.93% group significantly increased the activity of foregut protease(P<0.05), and 2.36%, 2.64%, 2.93%and 3.24% group significantly increased the activity of foregut amylase(P<0.05). Compared to the 1.76%group, 2.36%, 2.64% and 2.93% group significantly increased the activity of midgut protease(P<0.05). The dietary arginine levels had no significant effect on the activity of midgut amylase, hindgut protease and amylase(P>0.05). The dietary arginine levels had no significant effect on the activity of hindgut protease and amylase(P>0.05).Compared to the 1.76% group, the lipase activity in the intestine showed a rising trend with theincrease of dietary arginine levels, but the differences were not significant(P>0.05).(6) Compared to the 1.76% group, 2.64% group significantly increased the activity of serum nitric oxide synthetase(P<0.05); 2.36%, 2.64% and 2.93% group significantly increased the content of serum nitric oxide(P<0.05). Compared to the 1.76% group, the liver nitric oxide synthetase activity of other groups were significantly increased(P<0.05); 2.05%, 2.36%, 2.64% and 2.93% group significantly increased the content of liver nitric oxide(P<0.05). What’s more, GH and IGF-I relative gene expression were significantly enhanced with dietary arginine supplementation from 1.76% to 2.64%(P<0.05). The 2.64% group had the highest abundance, and it was 3.35- and 3.15-fold higher than the 1.76% group, respectively. The GH and IGF-I relative gene expression had no significantly differences with further dietary arginine supplementation(P>0.05).(7) Compared to the 1.76% group, 2.36%, 2.64% and 2.93% group significantly increased the fold height and muscular thickness of foregut(P<0.05); 2.93% group significantly increased the villus width of foregut(P<0.05). Compared to the 1.76%group, 2.64%, 2.93% and 3.24% group significantly increased the fold height of midgut(P<0.05). Different dietary arginine levels had no effect on villus width and muscular thickness of midgut, and it also had no effect on hindgut morphology(P>0.05).It is concluded that dietary appropriate arginine levels has a positive effect on the protein utilization rate and nitrogen deposition of fish, and enhance the antioxidative state of fish, and promote the development of intestinal morphology, and enhance the activities of intestinal digestive enzyme, and promote the absorption and metabolism of nutrients. What’s more, dietary appropriate arginine levels can up-regulate the relative expression of liver GH and IGF-I genes, modulate the correspond hormone release of body to promote the growth of fish. Quadratic regression analysis on specific growth rate, weight gain and feed efficiency ratio indicated that the optimal dietary arginine requirement for juvenile hybrid sturgeon was estimated to be 2.90%, 2.89% and 3.03%,respectively.