Feeding Strategy And Apparent Digestibility Coefficients Of Various Feed Ingerdients For Thamnaconus Septentrionalis Juvenile

The farmed Thamnaconus septentrionalis juvenile were taken as the research object in this article,we analyzed its feeding strategy and apparent digestibility coefficients of various feed ingerdients.Results of the study are presented as follows:1. To investigate the diet feeding rhythm and gastric emptying model of T.septentrionalis juvenile,a once-per-day satiation feeding treatment（one day was divided into eight time periods,each time period was used as one treatment,and the fish of each treatment were fed to apparent satiation once a day）and a continuous feeding treatment with fixed intervals（one day was divided into eight time periods,the fish in each tank were fed to apparent satiation,eight times a day）were conducted for 7 days.The experimental fish（4.28±0.46）g were removed at various intervals（0,2,4,6,8,10,12,14,16,20,24,and 28h）after satiation feeding.The wet mass of the chyme was determined and the applicability of the three mathematical models（linear model,exponential model,and square root model）was compared by the fitness of gastric evacuation data in T.septentrionalis juvenile.The results showed that（1）T.septentrionalis exhibit a 24h diet feeding cycle under two feeding scenarios.The feeding rate under the continuous feeding mode was not significantly different at 3:00,6:00,9:00,and 12:00,but decreased rapidly after reaching a peak at 15:00（P<0.05）,and at 0:00 reached the lowest value（P<0.05）.The feed efficiency was not significantly different at 3:00,6:00,15:00,and 18:00 in the once-per-day satiation feeding,and the specific growth rate was significantly higher than that of a once-per-day satiation feeding（P<0.05）.（2）The feeding rate of experimental fish decreased rapidly after 18:00 in the continuous feeding with a fixed interval（P<0.05）,and reached the lowest value at 0:00（P<0.05）.The specific growth rate and feed efficiency at 09:00-12:00 in the experimental fish were significantly higher than at the other times of the day（P<0.05）,Optimal feeding times in T.septentrionalis culturing were during 09:00-12:00.（3）Among the three models,the gastric emptying rate was best fitted to the square root model,and the equation was y^0.5=2.802?0.204t（R²=0.987）.According to the square root model,the 100%gastric emptying time was 10 h and the80%was 6 h,3h can reach a higher level of 41%.Based on the above indicators,it is recommended to feed the T.septentrionalis 3 times per day during the production practice from 9:00 to 15:00,with an interval of 3 h.2. A 30 days growth trial was conducted on T. septentrionalis juvenile to determine the effect of feeding frequency on their growth performance and antioxidant enzyme activity in liver.In the experiment,fish[body weight（6.18±0.86）g]were fed commerical feed at 5 feeding frequencies,including one meal per day at feeding on 12:00（F1）,two meals per day at feeding on 9:00 and 15:00 respectively（F2（1））,two meals per day at feeding on 6:00 and 18:00 respectively（F2（2））,three meals per day at feeding on 6:00,12:00,and 18:00（F3（1））or 9:00,12:00,and 15:00（F3（2））,four meals per day（F4）and five meals per day（F5）.Three replicates with 30 fish per barrel were assigned randomly to each feeding frequency.The results showed that:（1）From one meal per day to four meals per day,the feeding rate,weight gain rate and specific growth rate of T.septentrionalis juvenile were gradually increased（P<0.05）;the frequency of once per day was significantly lower than other feeding frequencies（P<0.05）,the HSI at four meals per day and five meals per day were significantly higher than other groups（P<0.05）.（2）The crude protein content of the experimental fish gradually decreased with the increase of the feeding frequency（P>0.05）,and the crude fat content continued to increase（P<0.05）.The crude fat content of the five times per day group was compared with once per day group increased about 5%,there was no significant difference in water content of each group（P>0.05）;with the increase of feeding frequency,trypsin activity showed a downward trend after the first rise,the lowest value was foud at three meals per day（P<0.05）;the lipase activity of four times per day and five times per day was significantly higher than the other three groups（P<0.05）,and there was no difference among the amylase groups（P>0.05）.（3）With the increase of the feeding frequency,there was no significant difference in the AKP activity of the experimental fish liver（P>0.05）,CAT,SOD and MDA activity showed an increasing trend（P<0.05）,the CAT in the five times per day group was significantly higher than the other 4 groups（P<0.05）;the SOD activity in the once per day and three times per day groups was significantly lower than the four times per day and five times per day（P<0.05）;MAD content in the four times per day and five times per day was significantly higher than the other 3 groups（P<0.05）.（4）In the range of twice per day to three times per day,changing the feeding time has a significant effect on the feeding rate,weight gain rate and specific growth rate（P<0.05）,but three times per day had no significant effect;the HSI ratio of the F3（2）group was significantly higher than the other three groups（P<0.05）,and there were no significant differences in condition factor,VSI,digestive enzyme activity and antioxidant enzyme activity（P>0.05）.To sum up,under this experimental condition,the optimal feeding frequency of the T.septentrionalis juvenile is three meals per day.3. This experiment was conducted to determine the apparent digestibility of dry matter（DM）,crude protein（CP）,crude fat（CF）and amino acids（AA）in domestic fish meal,soybean meal,peanut meal,cottonseed meal and rapeseed meal for T.septentrionalis juvenile.The experimental diets were consisted of 70%basal diet and30%test feed ingredients,and added 0.5%Y₂O₃as a exogenous indicator.Five hundred and foutyen T.septentrionalis juvenile[23.94±0.48g]were randomly divided into 6groups with 3 replicates in each group and 30 fish in each replicate,farmed in 18 barrels of indoor flow aquaculture system（200L）.The fish in control group were fed a basal diet,and those in experiment groups were randomly fed one of five test diets.The fecal samples were collected by siphon method after feeding one week.The results showed that:（1）The range of apparent digestibility of the DM was 52.20%-75.08%,the order from high to low was fish meal（75.08%）,peanut meal（63.84%）,rapeseed meal（59.69%）,cottonseed meal（54.33%）,soybean meal（52.20%）.（2）The apparent digestibility of CP of fish meal and peanut meal were above 91%,which higher than other feed materials,and there is no significant difference between them（P>0.05）.The apparent digestibility of CP of soybean meal,cottonseed meal and rapeseed meal were73.35%,79.35%and 78.84%,the protein digestibility of cottonseed meal and rapeseed meal were significantly higher than soybean meal（P<0.05）,but there is no significant difference between them（P>0.05）.（3）The fat apparent digestibility of the five raw materials used in the experiment were all above 93%.The apparent digestibility of fish meal was significantly higher than soybean meal and peanut meal（P<0.05）,reaching99.81%.There was no significant difference between the other four raw materials（P>0.05）.（4）The apparent digestibility of the total AA of the T.septentrionalis juvenile was in the range from 73.25%to 89.69%,which was consistent with that of CP in the five feed ingredients.The apparent digestibility of AA in fish meal and peanut meal was relatively high,reaching more than 86%,which was significantly higher than rapeseed meal,peanut meal and soybean meal（P<0.05）,and there was no significant difference between them（P>0.05）.In conclusion,fish meal and peanut meal were excellent protein sources of T.septentrionalis juvenile.While,the apparent digestibility of CP was in higher in soybean meal,cottonseed meal and rapeseed meal,but some AA is lower in them,which should be controlled in feed for T.septentrionalis juvenile.