| Feeding experiments were conducted to determine the effects of dietary proteinlevels, dietary lipid levels, different protein source, and different lipid source on thegrowth and feed utilization of southern catfish (Silurus meridionalis Chen) andcatfish (Silurus asotus Linnaeus). Results of the studies are presented as follows:1．A4×3two factor experiment was designed to evaluate the optimal dietaryprotein and lipid level for the juveniles of two species of catfish, Silurus meridionalisChen, the initial weight of which was about9.2g. Twelve practical diets wereformulated to contain four protein levels (46%,43%,40%,37%), each with three lipidlevels (13%,10%,7%), using fish meal and soybean meal as protein source, soybeanoil as lipid source. Each diet was fed to a triplicate group of catfish for8weeks in aflow-though water system. The results showed that the weight gain rate (WGR) of S.meridionalis Chen was not significantly affected by dietary lipid (P>0.05). However,dietary protein had significant effects on WGR of S. meridionalis Chen. In the groupwith7%dietary lipid, WGR of S. meridionalis chen firstly increased with theincreasing level of dietary protein, the highest value which was significantly higherthan the other groups (P <0.05) was found in S. meridionalis Chen fed with46%dietary protein level. In the group with10%dietary lipid, WGR of S. meridionalischen firstly increased with the decreasing level of dietary protein, and then decreased,the highest value was found in S. meridionalis Chen fed with43%dietary protein.The same change trend of WGR of S. meridionalis Chen was found in the group with13%dietary lipid, but the highest WGR was found in40%dietary group. With theincreasing level of dietary lipid, the need of maximum dietary protein for S.meridionalis Chen decreased, it was suggested that dietary lipid had protein-sparingeffect on this catfish.Dietary protein significantly affected feed intake (FI), feed efficiency ratio (FER),protein efficiency ratio (PER) of S. meridionalis Chen (P <0.05), but not dietary lipidor their interaction (P>0.05). Among all dietary lipid treatments, FI increased withthe decreasing of dietary protein level (r=-0.811, p=0.000;), and the lowest dietary protein level (37%) significantly increased FI (P<0.05), no significant differenceswere found among the other dietary protein groups.FER had the opposite change trend with FI and was positively related withdietary protein (r=0.820, p=0.000). PER was negatively related with dietary protein(r=-0.693, p=0.000), the group with highest dietary protein and highest dietarylipid (P46/L13) had the lowest PER and significantly lower than the other group(P<0.05).There were no significant differences in deinternal organ ratio, condition factor(CF) and hepatosomatic index (HI). Viscerasomatic index (VI) were significantly(P<0.05) increased by dietary lipid, but not dietary protein. Dietary protein and lipidhad significant effect on HV (P<0.05). when dietary protein level was37%~43%,there were no significant effect on HV among different dietary lipid treatments. Whendietary protein level was46%, the values of VSI significantly increased with theincreasing of dietary lipid levels, moreover, the HV with dietary13%lipid wassignificantly higher than that with dietary7%lipid.Based on the data of WGR, using piece-wise linear analysis, the optimal dietaryprotein for S. meridionalis was40.46%when dietary lipid was7%,43.40%whendietary lipid was10%and46.00%when dietary lipid was13%.Based on the results of WGR, FER, PER, and VI, low dietary protein had thelowest FER. So the optimal dietary protein and lipid requirement of S. meridionaliswas estimated to be43%and7%~10%respectively.2．A4×3two factor experiment was designed to evaluate the optimal dietaryprotein and lipid level for the juveniles of two species of catfish, Silurus meridionalisChen, the initial weight of which was about9.1g. Twelve practical diets wereformulated to contain four protein levels (46%,43%,40%,37%), each with three lipidlevels (13%,10%,7%), using fish meal and soybean meal as protein source, soybeanoil as lipid source. Each diet was fed to a triplicate group of catfish for8weeks in aflow-though water system. The results showed that there were no significantdifference between Survival rate，SR and weight gain rate (WGR) of S. asotusLinnaeu (P>0.05).Dietary protein significantly affected feed intake (FI), feed efficiency ratio (FER),protein efficiency ratio (PER) of S. meridionalis Chen (P <0.05), but not dietary lipidor their interaction (P>0.05). Among all dietary lipid treatments, FI was negatively related with the dietary protein level (r=-0.622, p=0.000;), and when dietary lipidwas13%or7%, the lowest dietary protein level (37%) significantly increased FI(P<0.05); when dietary lipid was10%, the lowest dietary protein level (37%)increased FI although no significant differences were found (P>0.05). FER had theopposite change trend with FI (r=-0.980, p=0.000) and was positively related withdietary protein (r=0.630, p=0.000). Among all the dietary lipid groups, the FERincreased with the increasing level of dietary protein. PER was negatively related withdietary protein (r=-0.488, p=0.000), the group with highest dietary protein anddietary10%lipid (P46/L13) had the lowest PER and significantly lower than P40/L7and P43/L7(P<0.05).Although there were no significant difference in the growth of S. meridionalis,but the group with37%dietary protein had low FER and the group with46%dietaryprotein had low PER. Based on the data of growth and feed utilization, the optimaldietary protein and lipid were estimated to be40%~43%and7%~10%respectively.3. A feeding experiment was studied to determine the effect of dietary rapeseedmeal on the survival, growth and feed utilization of southern catfish Silurusmeridionalis Chen (initial weight about11.5g). Fish meal, soybean meal andrapeseed meal were used as the protein sources. Soybean oil was used as the lipidsource. Wheat meal was used as the carbohydrate source. Seven practical diets wereformulated in a single factor design to contain seven levels of rapeseed meal0%,3%,6%,9%,12%,15%and18%, replacing0%,4.55%,9.09%,13.64%,18.18%,22.73%,27.27%of fishmeal. Each diet was fed to a triplicate group of catfish for8weeks in aflow-though water system. The results showed that there were no significantdifferences in the Survival rate，SR, weight gain ratio (WGR), feed intake (FI), feedefficiency ratio (FER), protein efficiency ratio (PER), and the moisture, crude protein,crude lipid, and ash in muscle (P>0.05). The dietary rapeseed meal had nosignificant effect on the deinternal organ ratio, condition factor, hepatosomatic index(P>0.05). Viscerasomatic index (VI) significantly increased when fish meal wasreplaced27.27%(P <0.05). The cholesterol and urea nitrogen in serum, the alanineaminotransferase and aspartate amino-transferase in liver, pepsin, ereptase, stomachamylase and intestine amylase showed no significant differences in differenttreatments (P>0.05).In conclusion, when dietary rapeseed meal increased to18%, as fish meal was replaced27.27%, there were no significant differences in the growth, survival andfeed utilization, except that VI significantly increased. So it was estimated that thehighest fish meal replacement was27.27%at least according to the results in thisexperimental condition.4. A feeding experiment was studied to determine the effect of dietary rapeseedmeal on the survival, growth and feed utilization of southern catfish Silurus asotusLinnaeus (initial weight about12.4g). Fish meal, soybean meal and rapeseed mealwere used as the protein sources. Soybean oil was used as the lipid source. Wheatmeal was used as the carbohydrate source. Seven practical diets were formulated in asingle factor design to contain seven levels of rapeseed meal0%,3%,6%,9%,12%,15%and18%, replacing0%,4.55%,9.09%,13.64%,18.18%,22.73%,27.27%offishmeal. Each diet was fed to a triplicate group of catfish for8weeks in aflow-though water system.The results showed that there were no significant differences in the survival ofSilurus asotus Linnaeus (P>0.05). However, the supplementation of rapeseed mealsignificant decreased the special growth rate (SGR)(P <0.05). The different level ofdietary rapeseed meal had no significant difference on the SGR (P>0.05). Themoisture, crude protein, crude lipid, and ash in muscle, the feed intake, feed efficiencyratio, protein efficiency ratio, apparent digestibility, apparent protein digestibilityshowed no significant difference between different treatments.The morphological indices, deinternal organ ratio, condition factor,hepatosomatic index, viscerasomatic index showed no significant difference betweendifferent treatments.The supplementation of rapeseed meal decreased the liver alanineaminotransferase significantly (r=-0.949, p=0.000).when fish meal was replaced9.09%, the liver alanine aminotransferase decreased significantly. There was nosignificantly difference between9.09%-18.18%, but22.73%is significantly decreasedthan9.09%. There was no significantly difference between13.64%-22.73%, but27.27%is significantly decreased than13.64%and18.18%. When fish meal wasreplaced22.73%, liver aspirate amino-transferase significantly decreased (P <0.01),There was no significantly difference between22.73%and27.27%. Thesupplementation of rapeseed meal decreased pepsin significantly (r=-0.766，p=0.000), when fish meal was replaced22.73%, pepsin decreased significantly, and when it s reach27.27%, pepsin further significantly decreased. The supplementationof rapeseed meal decreased ereptase significantly too(r=-0.885; p=0.000), when fishmeal was replaced18.18%, ereptase decreased significantly, and when it s reach27.27%, pepsin further significantly decreased.In conclusion, the supplementation of rapeseed meal in extruded feed woulddecrease SGR of Silurus asotus Linnaeus. The supplement of rapeseed meal of3%~18%, replacing4.55-27.27%fish meal, and showed no significant effect on thesurvival, growth and feed utilization.Because the difficulty in extruded production technique, the supplement of morethan18%(replacing more than27.27%fish meal) of rapeseed meal could not be usedin the experiment.5. A single factor experiment was studied to discuss the different lipid source onthe survival, growth and feed utilization of southern catfish Silurus meridionalis Chen(initial weight:11.50±0.02g). Fishmeal and soybean meal were used as the proteinsource, wheat flour was used as carbohydrate source. Four practical diets wereformulated to feed to a triplicate group of catfish for8weeks in a flow-though watersystem. The lipid source was soybean oil, fish oil, rapeseed oil and beef tallowrespectively in four experimental feed.The results showed that the survival and growth had no significant differencebetween different lipid source treatments (P>0.05).There were no significant differences in the feed intake, feed efficiency ratio,protein efficiency ratio between different treatments.The apparent digestibility were rapeseed oil, fish oil, soybean oil and beef tallowfrom high to low, and the value in rapeseed oil group was significantly higher thanthat in the others. There were no significant difference between the fish oil, soybeanoil and beef tallow groups.The four lipid source had no significant effect on moisture, crude protein, crudelipid and ash in the muscle, on the deinternal organ ratio, ondition factor,hepatosomatic index, viscerasomatic index.The serum cholesterol in beef tallow group was significantly higher than that inthe other group (P <0.01). The serum nitrogen in rapeseed oil group was significantlylower than that in beef tallow group and soybean oil group (P <0.01). The liveralanine aminotransferase and liver aspirate amino-transferase showed no significantdifference between different treatments (P>0.05). The pepsin, ereptase, stomach amylase and intestine amylase showed nosignificant differences in different treatments (P>0.05).In the experiment, the supplement of lipid source was4.5%, which is more thanhalf the dietary lipid. Different lipid source had no significant effect on the survival,growth and feed utilization, which suggested that soybean oil, fish oil, rapeseed oiland beef tallow are optimal for Silurus asotus Linnaeus in extruded feed.6. A single factor experiment was studied to discuss the different lipid source onthe survival, growth and feed utilization of southern catfish Silurus asotus Linnaeus(initial weight about12.3g). Fishmeal and soybean meal were used as the proteinsource, wheat flour was used as carbohydrate source. Four practical diets wereformulated to feed to a triplicate group of catfish for8weeks in a flow-though watersystem. The lipid source was soybean oil, fish oil, rapeseed oil and beef tallowrespectively in four experimental feed.The results showed that the survival and growth had no significant differencebetween different lipid source treatments (P>0.05).The feed intake were fish oil, beef tallow, soybean oil and rapeseed oil form highto low, and the value in fish oil group was significantly higher than the other group (P<0.01), beef tallow group was significantly higher than rapeseed oil group (P <0.01).The feed efficiency ratio and protein efficiency ratio were rapeseed oil, soybeanoil, beef tallow oil and fish oil form high to low. There were no significant differencein feed efficiency ratio and protein efficiency ratio between rapeseed oil, soybean oil,beef tallow oil groups, but the fish oil group was significantly lower than rapeseed oilgroup(P<0.05). Moreover, the feed efficiency ratio was positively related with proteinefficiency ratio (r=0.990, p=0000). The feed efficiency ratio and protein efficiencyratio are negatively related with feed intake (r=-0.839, p=0.000; r=-0.801, p=0.002).Different lipid source feed had no significant effect on the apparent digestibilityand protein digestibility respectively (P>0.05).The four lipid source had no significant effect on moisture, crude protein, crudelipid and ash in the muscle, on the deinternal organ ratio, ondition factor,hepatosomatic index. Viscerasomatic index were fish oil, rapeseed oil, beef tallow andsoybean oil from high to low. Viscerasomatic index in fish oil group was significantlyhigher than that in soybean oil and rapeseed oil group (P <0.01), rapeseed oil groupwas significantly lower than that fish oil and beef tallow group(P <0.01).The serum cholesterol were fish oil, rapeseed oil, beef tallow and soybean oil from high to low, and fish oil group was significantly higher than the other group (P<0.01). The serum nitrogen had the same change trend with serum cholesterol, thevalue in fish oil group and rapeseed oil were not significantly different (P>0.05), butboth the two group were significantly higher than beef tallow and soybean oil group(P <0.05).The pepsin, ereptase, stomach amylase and intestine amylase showed nosignificant differences in different treatments (P>0.05).In the experiment, soybean oil, fish oil, rapeseed oil and beef tallow in extrudedfeed had no significant effect on the survival, growth and feed utilization for Silurusasotus Linnaeus. |
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