| This thesis was conducted to investigate the effects of dietary arginine levels on growth performance, body composition, serum biochemical indices, immunity function, oxidation resistance, anti-ammonia-nitrogen stress ability and intestinal health indices of yellow catfish(Pelteobagrus fulvidraco). The contents and results are as follows:1. Effects of dietary arginine levels on growth performance, body composition and serum biochemical indices of yellow catfishFive isonitrogenous and isolipidic test diets(42% protein and 9% lipid) were formulated to contain graded levels of arginine 2.44%, 2.64%, 2.81%, 3.01% and 3.23%. Seven hundred juvenile yellow catfish with an initial average body weight of 1.13±0.02 g were randomly divided into 5 groups with 4 replicates of 35 fish each and fed the five diets respectively. The feeding trail was lasted for 56 d. The results showed that with the increasing of dietary arginine, the weight gain rate(WGR), specific growth rate(SGR), protein efficiency ratio(PER) and feed efficiency(FC) firstly increased and then decreased, and the best performance was observed in 2.64% group. Compared with 3.23% group, WGR, SGR in 2.64% and 2.81% groups were significantly increased(P<0.05), while FCR in 2.64%, 2.81% and 3.01% group was significantly decreased(P<0.05). The PER in 2.64% group was significantly higher than in 2.44% and 3.23% group(P<0.05). The condition factor(CF) in 2.81% group was significantly increased when compared with 2.44% group(P<0.05). Dietary arginine levels had no significant effect on hepatosomatic index(HSI), viscerosomatic index(VSI), and whole-body dry matter, crude protein, crude lipid, ash contents, as well as serum total protein, triglyceride, high density lipoprotein, low density lipoprotein, urea nitrogen, glucose contents and aspartate aminotransferase, alanine aminotransferase activities(P>0.05). A quadratic regression analysis on weight gain rate against dietary arginine levels indicated that the optimal dietary arginine requirement of juvenile yellow catfish was estimated to be 2.74% of the diet(corresponding to 6.45% of dietary protein).2. Effects of dietary arginine levels on immunity function, oxidation resistance and anti-ammonia-nitrogen stress ability of yellow catfishAfter 56 d feeding trail, the serum and tissue samples were prepared to analyse the changes of immunity function and oxidation resistance. Fourteen healthy yellow catfish were randomly selected from each replicates to conduct ammonia-nitrogen stress test. The results showed that with the increasing of dietary arginine, the serum complement 3(C3) content showed a trend of decreasing first and then increased, achieving the lowest in 2.81% group, and the content was significantly decreased when compare with 2.44%, 2.64% and 3.23% group(P<0.05). The content of serum interleukin 1?(IL-1?) in 2.64%, 2.81%, 3.01% and 3.23% groups was significantly lower than 2.44% group(P<0.05), and serum interleukin 6(IL-6) in 2.44% and 2.64% groups was significantly higher than 2.81% group(P<0.05). The activity of intestinal alkaline phosphatase(AKP) in 2.64%, 2.81%, 3.01% and 3.23% groups was significantly increased when compared with 2.44% group(P<0.05). The activity of serum glutathione peroxidase(GSH-Px) in 2.64% group was significantly higher than 2.44% group(P<0.05), and catalase(CAT) in 2.64% group was significantly higher than 2.44%, 3.01% and 3.23% groups(P<0.05), the content of serum malondialdehyde(MDA) in 3.01% group was significantly lower than 2.64% group(P<0.05). With the increasing of dietary arginine, the activity of intestinal and intestinal mucosa CAT, intestinal and hepatopancreas total antioxidant capacity(T-AOC) increased, while the content of intestinal and hepatopancreas MDA decreased. Compared with 2.44% group, the activity of intestinal CAT in 2.81%, 3.01% and 3.23% groups, intestinal mucosa CAT in 2.81% group, intestinal T-AOC in 3.01% group, hepatopancreas T-AOC in 2.64%, 2.81%, 3.01% and 3.23% groups were significantly increased(P<0.05). The content of intestinal MDA in 2.64%, 3.01% and 3.23% groups, hepatopancreas MDA content in 3.01% group were significantly decreased when compared with 2.44% group(P<0.05) and intestinal MDA in 2.64% group was also significantly lower than 2.81% group(P<0.05). After 72 h of ammonia-nitrogen stress, the cumulative mortality rate in other groups were lower than 2.44% group and 2.81% group was decreased significantly(P<0.05), the relative protection rate was 78.1%.3. Effects of dietary arginine levels on intestinal health indices of yellow catfishAfter 56 d feeding trail, the intestine and intestinal mucosasamples were prepared to determine the intestinal digestive enzyme activities, intestinal morphology and intestinal function indices. The results showed that dietary arginine levels had no significant effect on intestinal protease, lipase and amylase activities(P>0.05). Compare with 2.44% group, intestinal fold height in 3.23% group was significantly increased(P<0.05). The intestinal muscularis thickness in 2.81% and 3.23% group were significantly increased when compared with 2.44% group(P<0.05), and that in 3.23% group also significantly higher than 2.64 group(P<0.05). The activities of intestinal glutamyl transpetidase(?-GT), Na+K+-ATPase, and the content of endothelin 1(ET-1), as well as the activity of intestinal mucosa nitric total oxide synthase(TNOS), inducible nitric oxide synthase(i NOS), Lactase, maltase and the content of arginine decarboxylase(ADC), ornithine decarboxylase(ODC) and arginase(ARG) were not significantly affected by dietary arginine levels(P>0.05). The activity of intestinal mucosa diamineoxidase(DAO) in 3.01% group was significantly lower than 2.44% group(P<0.05). Compared with 2.44% group, the activity of intestinal mucosa sucrose in 2.64% and 2.81% groups were significantly increased(P<0.05). |
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