投喂率对凡纳对虾中间培育生长、生理和水环境的影响

Effects of feeding rate on the intermediate cultivation of Penaeus vannamei

关键词:  投喂率  凡纳对虾  中间培育  养殖水环境  非特异性免疫  生长性能  综合得分

Key words:  Feeding rates  Penaeus vannamei  Intermediate cultivational stage  Aquaculture water environment  Non-specific immunity  Growth performance  Composite score

摘要:

中间培育是凡纳对虾(Penaeus vannamei)养殖的重要阶段，投喂率是影响此阶段养殖成效的重要参数。本研究开展为期30 d的养殖实验，研究3组投喂率(投喂率分别为体重的5%、7.5%、10%，分别命名为T5、T7.5和T10)对凡纳对虾中间培育养殖水质、微生物群落结构、非特异性免疫指标及生长性能的影响。实验期间，水体pH、盐度、温度及溶解氧均保持在适宜对虾生长的范围内。结果显示，随着实验进行，总氨氮(TAN)、亚硝态氮(NO2–-N)和化学需氧量(COD)浓度出现上升趋势，实验结束时，其浓度随投喂率升高呈现显著差异：T10>T7.5>T5。微生物群落结构分析表明，养殖水体的微生物群落丰富度和多样性随投喂率升高呈下降趋势，不同投喂率的优势门类均为变形菌门(Proteobacteria, 50.36%~67.53%)和拟杆菌门(Bacteroidetes, 12.09%~67.53%)；在属水平上，对凡纳对虾有害的弧菌(Vibrio)相对丰度在T10组最高(37.33%)、T5组最低(0.13%)；对其有益的假交替单胞菌(Pseudoalteromonas)相对丰度在T10组最低(0.28%)、T7.5组最高(9.78%)。凡纳对虾肝胰腺的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、酸性磷酸酶(ACP)和碱性磷酸酶(AKP)活性在T10组最低、T7.5组最高(P<0.05)。T7.5和T10组对虾的体长和体重均显著大于T5组(P<0.05)，但T7.5和T10组之间无显著差异(P>0.05)，投喂率与存活率呈负相关，且3组间存在显著差异(P<0.05)。利用因子分析对非特异性免疫指标和生长指标进行综合评价，结果表明，T7.5组得分最高，为0.92，凡纳对虾中间培育的投喂率在7.5%左右为宜。

Abstract:

Penaeus vannamei Boone is an important economic species in aquaculture. It has become the main species of shrimp cultured in China due to its fast growth rate, high yield, and delicious meat. Segmented culture, which is important for promoting the environmental adaptation of shrimp, reducing the negative impact of diseases and improving the success of culture, is considered one of the major methods of shrimp farming. The intermediate cultivation stage is an important stage of shrimp farming as it determines the success or failure of economic benefits. P. vannamei are usually reared in intensive aquaculture systems that are highly dependent on bait feeding, which makes optimizing feeding rates fundamental to obtaining farming benefits. The feeding rate is the amount of bait as a percentage of the body mass of the cultured object, which is an important factor affecting the shrimp factory farming. Feeding rate directly affects the survival and specific growth rate of the cultured species; an excessively slow feeding rate will slow the growth of cultured objects and affect the normal development, while an excessively high feeding rate will increase the cost of breeding and cause accumulation of residual bait, which reduces water quality and may even result in death of the cultured objects. Therefore, it is necessary to determine the appropriate feeding rate to improve baiting efficiency and to satisfy the needs of sustainable aquaculture. However, in the intermediate cultivation stage, the determination of feeding rates relies on farming experience and lacks a scientific basis. To the best of our knowledge, few scholars have analyzed the influencing mechanisms of different feeding rates on shrimp growth, physiology, and water environment separately from the perspectives of exogenous and endogenous factors; however, there is a lack of comprehensive studies on the combined effects of feeding rates. Therefore, there is an urgent need to elaborate on the intrinsic connections between different parameters, such as the growth and physiological indicators of P. vannamei, water quality, as well as the microbial communities in the culture environment. The main objectives of this study are (1) to analyze the effects of different feeding rates on water quality conditions, microbial community structure, non-specific immunity indicators, and the growth performance of shrimp during the intermediate cultivational stage; (2) to elucidate the interaction between feeding rates and different indicators; and (3) to determine the appropriate feeding rate of the intermediate cultivation of P. vannamei. In this study, three groups of feeding rates, namely T5 (5%), T7.5 (7.5%), and T10 (10%), were used to feed P. vannamei during the intermediate cultivation stage for 30 d. The effects of different feeding rates on water quality, microbial community structure, non-specific immune indices, and growth performance in the intermediate cultivation of P. vannamei were analyzed. During the experiment, water quality and shrimp growth were regularly tested, and pH, salinity, temperature, and dissolved oxygen were maintained in a range suitable for shrimp growth. At the end of the experiment, the hepatopancreas of shrimp was used for non-specific immunity activity testing, and the microbial community characteristics of different culture densities were analyzed using high-throughput sequencing technology (Illumina MiSeq). Results showed that the concentrations of total ammonia nitrogen (TAN), NO2–-N, and chemical oxygen demand (COD) gradually increased as the experiment continued, and significant difference could be observed at the end of the experiment, T10 > T7.5 > T5 (P<0.05). Analysis of the microbial community structure showed an increasing tendency in richness and diversity with increasing feeding rates. At the phylum level, Proteobacteria (50.36%–67.53%) and Bacteroldota (12.09%–67.53%) were dominant in all samples; at the genus level, the relative abundance of Vibrio (harmful to P. vannamei) was the highest at T10 (37.33%) and lowest at T5 (0.13%), while the relative abundance of Pseudoalteromonas (beneficial to P. vannamei) was the highest at T7.5 (9.78%) and lowest at T10 (0.28%). Results of the redundancy analysis showed that the microbial community in the culture water with a feeding rate of 5% was positively correlated with salinity and temperature, and salinity had greater effect on microbial communities than temperature. The microbial community with feeding rate of 7.5% and 10% was positively affected by TAN, COD, and pH, and the effect of TAN on microbial community was greater than that of COD and pH. The superoxide dismutase, catalase, alkaline phosphatase, and acid phosphatase activities were the highest in T7.5 and were the lowest in T10 (P<0.05). The final average weight and length of T7.5 and T10 were significantly greater than those of T5 (P<0.05), while there was no significant difference between T7.5 and T10 (P>0.05). Survival rate was the highest at T5 (83.12%) and lowest at T10 (68.52%), with a significant difference (P<0.05). Factor analysis showed that the highest overall score of 0.92 was achieved at T7.5. This study showed that a feeding rate of 7.5% could improve growth performance and non-specific immunity in P. vannamei, and T7.5 was recommended for the intermediate cultivation of P. vannamei. This study elucidated the interactions between feeding rates and different indicators and determined the appropriate feeding rate for the intermediate cultivation of P. vannamei. This study might help optimize the feeding rates for the intermediate cultivational stage with a view to providing technical guidance for the improvement of the success rate of P. vannamei.