| This study was conducted to investigate the effects of the optimum protein to energy ratio in diet,feeding strategies and apparent digestibility coefficients of selected feed ingredients,in order to provide reference for the nutrition of juvenile tiger puffer(Takifugu rubripes).The results are summarized as follows.1.Effects of dietary protein to energy ratios on growth performance and body composition of juvenile tiger pufferA growth experiment was conducted to determine the optimal dietary protein to energy(P/E)ratio for juvenile tiger puffer(initial average weight 14.95g).Nine practical diets were formulated to contain three protein levels(36%,42% and 48%),each with three lipid levels(8%,12% and 16%),in order to produce a range of P/E ratios(from 17.06 to 24.20 mg/k J).Juvenile tiger puffer were fed the experimental diets for 56 days.Based on two-way analysis of variance,the protein level,lipid level and protein to energy ratio of feed significantly affected the final weight,feed efficiency ratio(FER)and specific growth rate(SGR)(P<0.05).When Those three growth parameters in the 42% and 48% protein groups was significantly higher than that in the36% protein group(P<0.05),but there was no significant difference in the 42% and48% protein groups(P>0.05).Those three growth parameters in the 8% lipid group was significantly lower than that of the 12% lipid group(P<0.05),while no significant difference was observed between the 12% and 16% lipid groups(P>0.05).In addition,there was no significant interaction between feed protein and lipid levels on growthrelated indexes.One-way analysis of variance showed that the final weight,FER,and SGR were the highest in the Diet8(48/12)treatment,which were significantly higher than those in the Diet1(36/8),Diet2(36/12),and Diet3(36/16)treatments(P <0.05),and was no significant differences compared with the Diet 4(42/8),Diet 5(42/12),Diet 6(42/16),and Diet 7(48/8)treatments(P> 0.05).Considering growth performance and protein saving effect,these results suggest that the diet containing 42% protein and 12%lipid with P/E of 20.75 mg/k J is optimal for juvenile tiger puffer.2.Effects of feeding strategies on the growth performance,body composition,digestive enzyme activities and biochemical parameters of juvenile tiger puffer2.1 Effects of different feeding levels on the growth performance,body composition,digestive enzyme activities,protein metabolism-related parameters and index of water quality of juvenile tiger pufferTo determine the optimum feeding level for juvenile tiger puffer,an experiment was conducted to study the effects of different feeding levels on the growth performance,body composition,digestive enzyme activities,protein metabolism-related parameters and index of water quality of juvenile tiger puffer.The fish were randomly assigned into 8 groups with 3 replicates per group,including 5 groups(initial body weight: 15.57 g)treated with different feeding levels(2%,4%,6%,8%,and 10%).After the 28 d feeding trail,the increased feeding level significantly improved the final weight,feeding intake(FI),specific growth rate(SGR),hepatosomatic index(HSI),viscerosomatic index(VSI)of juvenile tiger puffer(P<0.05).In addition,the trypsinogen activities,lipase activities,GPT in the liver also increased significantly with the increasing feeding level of juvenile tiger puffer(P<0.05),but final weight,SGR,HSI,VSI,lipase activities,GPT had no significant difference in the 4%,6%,8% and10% feeding levels(P>0.05).However,chymotrypsinogen activities in the liver and BUN in the serum decreased significantly with the increasing feeding level(P<0.05),but there was no significantly difference in the 4%,6%,8% and 10% feeding levels(P>0.05).Overall,considering the results of this study and feeding cost,the optimum feeding strategy with regards to the feeding level for juvenile tiger puffer was suggested to be 4% of the body weight.2.2 Effects of different feeding frequency on the growth performance,body composition,digestive enzyme activities,protein metabolism-related parameters and index of water quality of juvenile tiger pufferTo determine the optimum feeding frequency for juvenile tiger puffer,an experiment was conducted to study the effects of different feeding frequencies on the growth performance,body composition,digestive enzyme activities,protein metabolism-related parameters and index of water quality of juvenile tiger puffer.The fish were randomly assigned into 3 groups with 3 replicates per group,including 3groups(initial body weight: 15.57 g)treated with different feeding frequencies(twice,three times and four times a day).After the 28 d feeding trail,the HSI and VSI decreased significantly with the increasing feeding frequency(P<0.05).Meanwhile,trypsinogen activities and lipase activities in the liver firstly increased with the increasing feeding frequency,but then decreased(P<0.05).The GPT and NO3-N decreased significantly with the increasing feeding frequency(P<0.05),but they had no significant difference between twice a day and three times a day.The growth performance,body composition had no significant difference in the 3 kinds of feeding frequencies.Overall,considering the results of this study,the optimum feeding strategy with regards to the feeding frequency for juvenile tiger puffer was suggested to be twice per day.3.Apparent digestibility coefficients of selected feed ingredients for juvenile tiger pufferApparent digestibility coefficients(ADCs)of dry matter,crude protein,crude lipid,gross energy,phosphorus and amino acids in white fish meal,Peruvian red fish meal,meat and bone meal,corn gluten meal,soybean meal,peanut meal,cottonseed meal and rapeseed meal were determined for juvenile tiger puffer(Takifugu rubripes)with initial mean body weight of 37.90 g.A reference diet and test diets that consisted of a 70 : 30 mixture of the reference diet to test ingredient were used with 0.1% Y2O3 as an external indicator.White fish meal,Peruvian red fish meal and soybean meal had higher ADCs of dry matter,dry matter ADCs ranged 43.35%~70.54% among ingredients tested.Protein ADCs of feed ingredients ranged 50.91%~92.78%,meat and bone meal had significantly lower ADCs of protein compared with that of white fish meal,Peruvian red fish meal,soybean meal,peanut meal,rapeseed meal and DDGS(P<0.05).Amino acid ADCs generally reflected protein digestibility.ADCs of lipid were relatively high in the ingredients tested.Energy ADCs of feed ingredients ranged30.58%~90.01%,white fish meal,Peruvian red fish meal,soybean meal and peanut meal had significantly higher ADCs of energy(76.26%~90.01%).Phosphorus ADCs of feed ingredients ranged 9.13%~68.14%,white fish meal,Peruvian red fish meal had significantly higher ADCs of phosphorus among ingredients tested.In conclusion,ADCs of dry matter,crude protein,crude lipid,gross energy,phosphorus and amino acids in white fish meal,Peruvian red fish meal were higher,while ADCs of dry matter,crude protein,crude lipid,gross energy,phosphorus and amino acids in meat and bone meal and corn gluten meal were lower compared with that other tested ingredient for tiger puffer.Soybean meal and peanut meal had higher ADCs of protein and essential amino acids in plant protein ingredients.Resultant digestibility data may provide useful information to commercial tiger puffer feed industry. |
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