Effects of Feeding Rate on the Intermediate Cultivation of Penaeus vannamei

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). 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.

Keywords

• feeding rates
• penaeus vannamei
• intermediate cultivational stage
• aquaculture water environment
• non-specific immunity
• growth performance
• composite score