The metabolic consequences of the isoenergetic replacement of dietaryprotein by carbohydrates (CHO) were compared in studies of European eel andrainbow trout. Diets with 45/20, 37/30, 29/40 and 21/50 percentprotein/carbohydrate were assessed during a 12-week experiment. The CHO sourcewas pre-gelatinized corn starch. Fish of initial average weight 45gwere fed to satiation twice daily. Weight-gain and feed-efficiency data weregenerally better in trout than in eel, presumably because trout digestibilitycoefficients for protein and energy were higher than in eel. In both species,regardless of physiological differences in digestion and absorption, feedintakeand nutrient digestibility were lower when dietary CHO was higher, but theinter-species differences decreased with increasing dietary CHO.Pyruvate kinase activity (PK) in trout was not affected by dietary CHO content,while blood-glucose and liver-glycogen levels significantly rose withincreasingdietary CHO. In contrast, blood-glucose levels appeared to be regulated ineels,perhaps by an accelerated glycolysis rate, revealed by changes in PK.Gluconeogenic activity was inhibited in trout fed a diet containing20–30%CHO, while in eels this activity was not inhibited by dietary replacement ofprotein by carbohydrate. Liver glucose 6-phosphate dehydrogenase activity(G6PDH) was inhibited in trout fed increasing dietary CHO, whereas in eelsG6PDHoperated at a high rate regardless of dietary composition. These results mayindicate that eels have a better capacity for metabolising high-CHO/low-proteindiets than do trout. 相似文献
A growth experiment was conducted to determine the optimal dietary protein requirement for juvenile ivory shell reared in indoor aerated aquaria. Six isoenergetic experimental diets using fish meal, casein and gelatin as protein sources were formulated to contain graded levels of protein (27, 33, 38, 43, 49 and 54% of dry diet, respectively). Triplicate groups of 40 shells (average weight 93.50 ± 1.70 mg) were stocked in 120-l tanks and fed to apparent satiation twice daily for 8 weeks. The results showed that the growth performance and feed utilization were significantly affected by dietary protein level (P < 0.05). Maximum weight gain, mean protein gain, specific growth rate and soft body to shell ratio occurred at 43% dietary protein level (P < 0.05). There were significant differences in protein, lipid, moisture and ash content in soft body; except that ash content in shell was not significantly affected by dietary protein level. Pepsin activity in soft body tissue significantly increased with dietary protein level up to 43%, and trypsin-like enzyme activity increased with dietary protein level up to 49%. However, lipase activity in soft body decreased with increasing dietary protein level. However, no significant differences (P < 0.05) in survival, calcium, phosphorus concentration in the shell and soft body were found among dietary treatments. Quadratic regression analysis of weight gain against dietary protein level indicated that the optimal dietary protein requirement for maximum growth and feed utilization of juvenile ivory shell is 45% of dry diet. 相似文献
A trial was conducted in 12 purpose-built, commercial, drainable, earthen ponds to evaluate the effect of fish and plant protein and lipid source on the growth, condition indices, and body composition of marron (Cherax tenuimanus). Juvenile marron (1.3±0.28 S.E. g) at the stocking densities of three per square meter were fed for a period of 1 year with four different formulated isoenergetic practical diets (D1, D2, D3, and D4). Three of the test diets (D1, D2, and D3) were isonitrogenous whereas the fourth test diet (D4) was protein-free. Protein and lipid sources in D1 were from Lupin (Lupinus albus) whereas protein and lipid sources in D2 and D3 were from fish meal. Fish oil (3.5%) was added to D1, D3, and D4 whereas sunflower oil was added to D2 and D4 in order to make them isoenergetic. The four test diets were randomly allocated to three replicate ponds.
The lack of protein in D4 did not significantly influence (P>0.05) the mean final weight and specific growth rate of marron. Survival was low in all ponds (13.82–34.66%) but feeding with D4 resulted in a significantly (P<0.05) higher survival than marron fed with D1 and D2. Feeding a diet containing a combination of fish protein and fish oil (D3) resulted in significantly higher (P<0.05) wet tail muscles-to-body weight ratio than was observed with other diets. Tail muscles protein level of all marron was significantly lower (P<0.05) at the end of the trial than at the beginning. EPA and DHA in hepatopancreas and tail muscles of marron were affected by the four test diets. The inclusion of plant protein in formulated diets had a negative impact on the pond environment due to significantly higher unionised ammonia levels that resulted in lower survival. Juvenile marron fed with a plant protein diet had significantly lower protein levels in their hepatopancreas compared to those fed with diets containing animal protein. Feeding marron with lupin protein source (D1) and plant oil (D2) for 1 year did not alter the lipid content of their hepatopancreas. Four test diets had no influence on the fat content of marron hepatopancreas; however, these test diets significantly reduced the protein content of the tail muscles of marron.
Environmental variables, particularly temperature, nitrogen metabolites, and the natural productivity of the ecosystem, greatly influenced the nutritional requirements of the juvenile marron under culture. 相似文献