Effects Of Plant Energy Resource, Additive And Feeding Frequency On Growth Performance Of Juvenile Myxocyprinus Asiaticus

This study was conducted to evaluate the effects of plant energy resource, additive and feeding frequency on growth performance of juvenile Chinese sucker. The results were as followed.1. A feeding experiment was conducted to evaluate the potential of replacing fish meal (FM, Diet1)with fermented soybean meal (FSBM, Diet2), corn gluten meal(CGM, Diet3), soybean meal (SBM, Diet4) and cottonseed meal(CSM, Diet5) in practical diets of juvenile Chinese sucker. Diet containing FM as the main protein source was used as a control (Diet1). Diets2-5had30%of the FM protein replaced with FSBM, CGM, SBM or CSM protein. Fish (average weight,1.82±0.03g, mean±SD) were hand-fed for8weeks. At the end of the feeding trial, fish fed Diets1-4showed no significant difference in weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER), while fish fed Diet5showed significant inferior weight gain (WG,5.04g/fish), specific growth rate (SGR), feed conversion ratio (FCR,1.52) and protein efficiency ratio (PER,1.55). Body crude protein (15.78%) and crude lipid (4.92%) of the fish fed Diet5were significantly lower than those of the fish fed the other diets. Essential amino acids (EAAs) contents (%dry matter) of the fish showed significant differences among the different treatments. Digestive enzyme activities in the intestine and hepatopancreas of the fish fed Diet5were significantly lower than those of the fish fed Diets1-4. Results of the present study indicated that about30%of FM protein can be replaced by FSBM, CGM or SBM protein in Chinese sucker diets without adversely affecting growth.2. In experiment2, juvenile Chinese sucker (3.403.40±0.08g) was fed one of five experimental diets twice daily for8weeks. Dietl in experiment I were used as a control and Diet4(CSM) in experiment1, with ferrous sulfate, with lysine or with both ferrous sulfate and lysine were used as the experimental diets (designated as FM, CSM, CSM+Fe, CSM+L and CSM+Fe&L, respectively). Results from feeding trial indicated that about30%of FM protein can be replaced by CSM with lysine supplement in Chinese sucker diets without adversely affecting growth. The highest weight gain was found in group FM (12.01g/fish), littlely higher than groups CSM+L and CSM+Fe&L, but no significant difference. The SGR in groups FM, CSM+L and CSM+Fe&L were2.68,2.63and2.66, were significantly higher than groups CSM and CSM+Fe (both were2.25). The PER in in groups FM, CSM+L and CSM+Fe&L were significantly higher than groups CSM and CSM+Fe. The protein, lipid as well as lysine contents of fish body in groups CSM+L and CSM+Fe&L were significantly higher than groups CSM and CSM+Fe. The results indicated that cottonseed meal with lysine supplyment could replace30%fish meal in the diets for juvenile Chinese sucker without affecting growth performance.3. Six isonitrogenous diets with six levels of soybean meal in substitution offish meal (0,20,40,60,80and100%) were evaluated in Chinese sucker of1.81±0.01g (mean±SD) initial weight for8weeks. There existed a significant difference (P<0.05) in growth performance of fish when the replacement level for fish meal protein was increased from40%to60%, indicating that up to40%of fish meal protein could be replaced with soybean meal protein without causing reduction in growth and protein utilization. Lipid contents in the Chinese sucker body decreased significantly (P<0.05) as dietary soybean meal increased. Digestive enzyme activities in the intestine and hepatopancreas of the fish were significantly different (P<0.001) as the soybean meal protein replacement level was increased. Results of the present study appear to indicate that40%FM can be replaced by SBM in practical feeds of Chinese sucker.4. This study was designed to evaluate the effects of using soybean meal supplemented with or without methionine (M) and graded levels of phytase (P) to replace high level (60%) fish meal in the diets of juvenile Chinese sucker. Seven experimental diets (about430g kg-1crude protein on dry matter basis) were formulated from practical ingredients. The control feed (diet1) was formulated to contain400g kg-1white fish meal (FM), whereas in the other six feeds (diets2-7), soybean meal (SBM) was used to replace60%fish meal with or without methionine(3g kg-1) and0,500,1000,1500and2000U kg-1phytase (designated as SBM, S+M, S+M&P500, S+M&P1000, S+M&P1500and S+M&P2000, respectively). Results from the feeding trial indicated that SBM without any methionine or phytase supplement replacing about60%FM significantly affected the growth of fish. Growth of fish which fed diet S+M was improved compared with the group which fed diet SBM, but still much lower than fish fed the control diet. SBM with methionine and graded levels of phytase supplement significantly improved growth of fish and apparent digestibility coefficient of phosphorus compared with the groups which fed diet SBM and diet S+M. Fish fed S+M&P1500showed optimal growth performance and no significant difference compared with control group. This suggested that soybean meal with3g kg-1methionine and1500U kg-1phytase supplement could successfully replace60%fish meal in the diet for juvenile Chinese sucker without affecting growth of fish, and enhanced the apparent digestibility coefficient of phosphorus.5. A8weeks feeding experiment was carried out on juvenile Chinese sucker to evaluate the effects of dietary replacement of fish oil by soybean oil on fish growth,body composition and liver biochemical composition. Fish (average weight,13.7g) in triplicate were fed five diets, in which0%(FO as control),40%(SO40),60%(SO60),80%(SO80) and100%(SO100) offish oil was replaced by soybean oil. The weight gain offish fed SO40, SO60or SO80diet was similar to that of fish fed the control diet, but a total replacement of fish oil by soybean oil significantly reduced fish growth(P<0.05). Although the level of soybean oil resulted in an increase in the crude lipid content of the liver, the level of fish oil replacement did not significantly alter the hepatosomatic index and feed conversion ratio. The inclusion of soybean oil in Chinese sucker diets increased hepatic vitamin E concentrations, but reduced thiobarbituric acid-reactive substances (TBARS) and plasma cholesterol. Linoleic acid and linolenic acid significantly increased in fish liver fed soybean oil diets, but docosahexaenoic acid and the ratio n-3/n-6were significantly reduced by the inclusion of dietary soybean oil (P<0.05). Our results indicated that the inclusion of soybean oil increased the hepatic vitamin E content and reduced lipid peroxidation in fish. However, complete substitution of fish oil with soybean oil reduced growth efficiency. Thus,40-80%replacement of fish oil by soybean oil is recommended in diet formulation for juvenile Chinese sucker.6. A feeding trial was conducted to investigate the effects of feeding frequency on the growth performance, feed utilization and body proximate composition of juvenile Chinese sucker. Triplicate groups of fish (average weight,11.85g) were fed each feed type to visual satiation at four meals per day, three meals per day, two meals per day and one meal per day for8weeks. At the end of the feeding trial, Weight gain was affected by the feeding frequency. The highest weight gain was observed in the group which fish were fed three meals per day, significantly higher than fish fed one or two meals per day. There existed a significant difference in daily feed intake (DFI), feed conversion ratio (FCR) and protein efficiency ratio (PER) when the feedingn frequeny was increased from one or two to three or four meals per day (P<0.05), but no different with the fish fed four meals per day. The body proximate composition of fish was altered by feeding frequency. The crude lipid content increased with the increase of feeding frequency. The present findings suggest that three feedings per day may be sufficient for the maximal growth performance of juvenile Chinese sucker.