| Feeding trials were conducted to investigate the effects of dietary protein,lipid and carbohydrate ratio and various lipid sources on growth performance and body composition for bullfrog(Rana catesbeiana),which is the major culture species of amphibian animals in China.The optimal dietary protein to lipid ratio,carbohydrate to lipid ratio,and lipid sources were estimated for bullfrog.Results of the present study are presented as follows:1.Effects of dietary protein and lipid levels on growth of bullfrog,Rana catesbeianaA feeding trial was conducted to estimate the optimum dietary protein and lipid levels for bullfrog(Rana catesbeiana).Twelve diets were formulated to contain three protein levels(35%,40% and 45%),each with four lipid levels(4%,7%,10% and 13%),in order to produce a range of P/E ratios(from 21.9 to 32.0 mg protein/kJ).The designed dietary protein and lipid levels in a brown fish meal-based formulation were achieved by serial adjustment of casein(for protein)or a mixture of fish oil and soybean oil(for lipid)at the expense of microcrystalline cellulose.Each diet was randomly assigned to three tanks(200 L),each tank was stocked with 12 bullfrogs[(91.5±0.10)g average initial body weight].Bullfrogs were fed twice daily(08:00 and 17:00)to apparent satiation for 8 weeks.The results showed that no significant differences in survival were found among all dietary treatments,but bullfrogs fed the diet with 13% lipid appear liver lesions,such as abnormal color and crumbly texture.Weight gain(WG)and specific growth rate(SGR)of bullfrogs fed diet with 40% protein were significantly higher than that of bullfrogs fed diet with 35% protein(P<0.05),but no significant differences with bullfrogs fed diet with 45%protein(P>0.05).With increasing dietary protein levels,feed efficiency(FE)increased significantly(P<0.05),whereas,feed rate(FR)and protein efficiency ratio(PER)were just the opposite(P<0.05).WG,SGR and FR increased significantly with increasing dietary lipid levels(P<0.05),however,FE,PER and nitrogen retention efficiency were not significantly affected by dietary lipid levels(P>0.05).No significant difference was observed in body composition among all the groups at different dietary protein levels(P>0.05).Whole-body crude protein contents were not significantly affected by dietary lipid levels(P>0.05).However,whole-body crude lipid and energy contents increased significantly with increasing dietary lipid level(P<0.05).With increasing dietary lipid levels hepatic malondialdehyde(MDA)concentration increased significantly(P<0.05),whereas,hepatic catalase(CAT)and lipoprotein lipase(LPL)activitywere firstly increased and then decreased(P<0.05).The results of this study suggest that diet containing 40% protein and 7% lipid with a protein to energy ratio of 27.7 mg protein/kJ was optimal for bullfrog.2.Effect of dietary carbohydrate to lipid ratios on growth and body composition of bullfrog,Rana catesbeianaA feeding trail was conducted to determine the effects of dietary carbohydrate to lipid ratios on growth performance and whole-body composition of bullfrog(Rana catesbeiana).Using brown fish meal and casein as main protein sources,fish oil and soybean oil as main lipid source,corn starch as main carbohydrate source,and mixing with mineral mixture and vitamin mixture,seven isonitrogenous(40% crude protein)and isoenergetic(14.5 kJ/g avaliable energy)experimental diets were formulated with varying carbohydrate to lipid(CHO/L g/g)ratios of12.11(D1),6.10(D2),3.94(D3),2.76(D4),1.82(D5),1.20(D6)and 0.76(D7),respectively.Each diet was randomly assigned to three tanks(200 L),each tank was stocked with 15 bullfrogs(68.43±0.42 g average initial body weight).Bullfrogs were fed twice daily(08:00 and 17:00)to satiation for 8 weeks.The results showed that no significant differences in survival were found among all dietary treatments.With decreasing dietary CHO/L levels,Weight gain(WG)and specific growth rate(SGR)were increased and then leveled off(P<0.05).No significant differences were found in WG and SGR among D4,D5,D6 groups(P>0.05),and those group were significantly higher than those in D1 and D2 groups.There were no significant differenceson the feed efficiency,protein efficiency ratio,viserosomatic index and hepatosomatic of the bullfrog among dietary treatments.With decreasing dietary CHO/L levels,energy retention efficiency were increased and then reatched a plateau(P<0.05),and and the highest value was observed in D4 group.Whole-body crude lipid and energy contents increased significantly with decreasing dietary CHO/L levels,whereas,moisture was just the opposite(P<0.05).Muscle moisture,crude protein,crude lipid and ash contents were not significantly affected by dietary CHO/L levels(P>0.05).Hepatic crude lipid contents in D5,D6 and D7 groups were significantly higher than that in other groups(P<0.05).With decreasing dietary CHO/L levels,hepatic hexokinase and pyruvate kinase activities decreased significantly(P<0.05).Hepatic acetyl CoA carboxylase and glucose-6-phosphatase activities in D3 group were the highest in all groups(P<0.05).This study suggested that bullfrog can perform equally well on diets containing available carbohydrate ranging from 25.5 to 30% of the diet,with lipid content ranging from 9.3 to 7.6% or at CHO/L ratio of 2.76-3.94.3.Effects of dietary lipid sources on growth performance and body composition of bullfrog,Rana catesbeianaA feeding trial was conducted to estimate the effects of dietary lipid sources on growthperformance and body composition of bullfrog,Rana catesbeiana.Seven isonitrogenous and isoenergetic experimental diets were formulated using fish oil,embedding fish oil,chicken oil,lard,lecithin oil,soybean oil and palm oil as the lipid sources,respectively.Each diet was randomly assigned to three tanks(200 L),each tank was stocked with 12 bullfrogs [(83.50±0.10)g average initial body weight].Bullfrogs were fed twice daily(08:00 and 17:00)to apparent satiation for 8 weeks.The results showed that the weight gain rate(WG)and the specific growth rate(SGR)of bullfrogs fed diets supplemented with fish oil,soybean oil and palm oil were significantly(P<0.05)higher than that of bullfrogs fed other diets.Feed efficiency(FE),protein efficiency ratio(PER)and nitrogen retention rate of bullfrogs that fed embedding fish oil were significantly(P<0.05)higher than that of bullfrogs fed other diets,and there was no significant difference other groups(P>0.05).The moisture,crude protein,crude ash,crude lipid and energy contents of whole bullfrogs did not showed significant difference among all groups(P>0.05).The muscle moisture,crude lipid,crude protein content and energy of bullfrogs did not showed significant difference among all groups(P>0.05),but the lowest crude lipid content in bullfrog muscle was observed in the fish oil group,respectively.The content of cholesterol in the serum,lipoprotein lipase in the liver,lipase in the intestinal tract of fish oil group,soybean oil group and palm oil group were significantly higher than that of the other groups(P<0.05),while the triglyceride,the high-density lipoprotein cholesterol,low-density lipoprotein cholesterol in the serum,total antioxidant capacity,carnitine palmityl transferase-I and carnitine palmityl transferase-II in the liver,protease in the intestinal tract were not significantly different among all treatments.These results indicate that fish oil,soybean oil and palm oil were good alternative dietary lipid sources for bullfrogs.The results of the present study suggest that diet containing 40% protein and 7% lipid with a protein to energy ratio of 27.7 mg protein/kJ and a carbohydrate to lipid ratio of 2.76-3.94 with25.5 to 30% dietary available carbohydrate and 9.3 to 7.6% dietary lipid were optimal for bullfrog,and fish oil,soybean oil or palm oil were good alternative dietary lipid sources for bullfrog. |
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