| The purposes of this dissertation are to (1) study the utilization of dietary amino acids in teleost fish during early life stages (larvae and juvenile), (2) to investigate the effect of the indispensible amino acids (IDAA) imbalanced diets on young teleosts in terms of their body weight gain, feed intake, feed conversion rate and the concentrations of whole body (or muscle) free amino acids.; In the first set of experiments, we evaluated the utilization of synthetic dipeptide-based, FAA-based diets in early life stages of stomachless (common carp larvae and juvenile), or stomach possessing-fish (rainbow trout alevine and juvenile, or pacu juvenile). A live feed organisms (brine shrimp Artemia salina nauplii, AS) or casein-gelatin-based diet was used as protein control. These experiments were listed as Chapter 2 (Indispensable amino acid concentrations decrease in tissues of stomachless fish, common carp in response to free amino acid- or peptide-based diets), Chapter 3 Influence of different dietary arginine supplementation forms on hepatic arginase activity in juvenile Pacu (Piaractus mesopotamicus ) and comparative aspects of arginase activity in teleosts), Appendix 1 (A concept of dietary dipeptides: a step to resolve the problem of amino acid availability in the early life of vertebrates), and Appendix 2 (Free- and peptide-based dietary arginine supplementation for the South American fish pacu (Piaractus mesopotamicus)). Our results demonstrated that synthetic dipeptide-based diets but not FAA-base diet can sustain young rainbow trout and pacu optimal growth. On the contrary, neither synthetic-base or FAA-based diets can be utilized by common carp larvae.; In another set of experiments (including 2 experiments), we examined the effect of IDAA-imbalanced diets on juvenile teleost, and tested IDAA imbalance/complimentary feeding strategy that may eliminate the adverse effect of IDAA deficient diet on young fish. These experiments were listed as Chapter 4 (The effect of dietary amino acid imbalances on feed intake: Is there a neurological sensing of deficiency present in fish?), Chapter 5 (Postprandial and long-term effect of dietary imbalanced amino acid composition on the whole body free amino acid concentrations in teleost fish (Midas experiment 1)) and Chapter 6 (Whole body free IDAA were not depressed after feeding juvenile Midas (Amphilophus citrinellum) with IDAA imbalanced diets in alternate meals (Midas experiment 2)). In experiment 1, two IDAA imbalanced diets, (-)Lys diet (Lys, His, Ile, Phe and Trp in the diet were omitted) and (-)Arg diets (Arg, Thr, Val, Leu and Met in the diet were missing), and two IDAA balanced diets, casein-gelatin-based diet (protein control) and FAA-based diet (FAA control), were tested in juvenile midas (Amphilophus citrinellum) with 95.6 +/- 4.3 mg initial body weight. We found fish responded initially by a decreased feed intake, but two weeks into the experiment, fish fed (-)Arg or (-)Lys had a significantly increased intake of amino acid imbalanced diets. Fish fed FAA diet or IDAA imbalanced diet showed a decreasing trend in their whole body IDAA concentrations, which differ from the fish fed with protein diet. In experiment 2, three diets, FAA-based diet (control diet), (-)Lys and (-)Arg diets, were used. Juvenile midas with 135 +/- 10 mg initial body weight were provided with FAA imbalanced diets using several different feeding strategies. The principle was that within 2-day frame, all fish get the same amount of dietary IDAA throughout the 32-day experiment period. After 32 days, fish in all feeding treatments increased their body weight significantly, but the final weights linearly decreased with lower frequency of complimentary diets provision. Fish in the group fed with -Lys-Arg - Lys-Arg (interchangeably) had well balanced whole body IDAA and DAA profile (after the last meal of the day) and higher final body weight gain compared to other IDAA imbalanced diets-fed groups. I... |
