Ornithine is an arginine family amino acid and is not incorporated into protein. This study evaluated its role in growth, immune response and acute NH 3 stress tolerance of Penaeus vannamei . Six diets with graded levels (0.6, 0.9, 1.2, 1.5, 1.8, 2.1 g kg −1 ) of L-ornithine were formulated, and fed the shrimp for 8 weeks. The growth of shrimp was significantly improved with the dietary ornithine levels increased from 0.6 to 1.5 g kg −1 . Feed efficiency, protein efficiency ratio and protein productive value showed a similar trend to the growth performance of shrimp. Whole body protein and muscle lipid of shrimp were significantly increased in shrimp fed 1.8 g kg −1 ornithine compared to those fed 0.6 g kg −1 ornithine. The contents of several amino acids were increased with the dietary ornithine increased to 1.5 g kg −1 . Elevated levels of ornithine increased the Nitric Oxide (NO) content and suppressed arginase activity in the hemolymph. The relative mRNA expression of superoxide dismutase , heat shock protein 70 , dorsal and caspase 3 were increased with the dietary addition of ornithine, while the mRNA level of arginase was decreased with the increasing dietary ornithine levels. After 9 h acute NH 3 stress, mortality of shrimp reduced with the increasing dietary ornithine levels. The relative mRNA levels of superoxide dismutase , heat shock protein 70 , dorsal and catalase were increased with the dietary addition of ornithine after the acute NH 3 stress. The second-order regression analysis of weight gain and survival after acute stress revealed that the suitable ornithine content in the shrimp diet was 1.4–1.5 g kg −1 .
S.-W. Xie,Y.-T. Li,W.-W. Zhou,L.-X. Tian,Y.-M. Li,S.-L. Zeng,Y.-J. Liu
An 8-week feeding trial was conducted to evaluate the optimum dietary γ-aminobutyric acid (GABA) level in low fishmeal diet for juvenile Pacific white shrimp, Litopenaeus vannamei . Six practical diets (449 g kg −1 protein, 87 g kg −1 lipid) supplemented with graded levels of GABA (0, 50, 100, 150, 200, 250 mg kg −1 ) were formulated. Each diet was randomly assigned to triplicate groups of 30 shrimps (approximately 0.44 g), and the shrimps were fed four times a day to apparent satiation. Weight gain and gain rate were significantly increased with the supplementation of GABA ( P < 0.05). Hepatosomatic index and survival were also significantly influenced by the dietary GABA levels ( P < 0.05) and show a similar trend to those of growth performance. Insulin and neuropeptide Y concentrations in blood were increased with the supplementation of GABA. In total, 150 mg GABA kg −1 -supplemented diets significantly increased the survival after 12, 24 and 36 h of NH 3 stress, also increased the total antioxidant capacity, total superoxide dismutase, catalase, antihydroxyl radical and phenoloxidase activities before and after the 36 h NH 3 stress compared to basic group. These results clearly indicated that GABA could improve growth performance, antioxidative capacity and resistance against NH 3 stress in L. vannamei , and 150 mg kg −1 GABA supplementation was suitable for L. vannamei fed with low fishmeal diet.
Zhan Hu,Dantong Wang,Pengcheng Li,Yaoqi Hou,Guanyi Chen,Chunfeng Song
The CO 2 chemical absorption and microalgae conversion (CAMC) system can achieve low-energy consumption CO 2 capture and resource utilization, but the study on enhancing the synthesis of high-value products has been overlooked. In this study, the coupling strategy of nitrogen stress and exogenous phytohormones was applied to induce high-value products accumulation of Dunaliella salina in CAMC system, and the potential mechanism was also discussed. The results showed that phytohormones could promote D. salina growth by alleviating the oxidative damage under nitrogen limited treatment, especially in gibberellin (GA) group, and the biomass increased by 10.24%. In addition, phytohormones combined nitrogen limited changed carbon flow, directing more carbon to polysaccharose synthesis, supplementation with GA under nitrogen-limited conditions resulted in a 1.65-fold increase in polysaccharide content in D. salina compared to the control. Furthermore, supplementation with GA under nitrogen-limited conditions enhanced the accumulation of β-carotene, and the β-carotene yield and content were 18.52% and 14.46% higher than control. This study suggested that GA could further affect carbon metabolism and products synthesis of D. salina under nitrogen stress, and provided a possible insight in improving the production of economical metabolites in CAMC system.
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