The effects of different feeding rates and re-feeding of Litopenaeus vannamei in a biofloc culture system

Abstract

The natural productivity in biofloc culture systems could be an important source of supplementary food to shrimp, representing savings in artificial feed. The aim of the present study was to evaluate the effects of using different feeding rates for a period of 21days with a posterior re-feeding period in a microcosm system in the presence of bioflocs. Litopenaeus vannamei juveniles (1.14±0.38g) were stocked at 400 shrimp m−3 in 150-L tanks in a biofloc recirculation system in two phases. The feeding rates were calculated considering an expected weekly growth of 1g week−1 and an estimated weekly mortality of 0.5%; each treatment corresponded to a different feeding rate, and each feeding rate corresponded to a fixed food conversion ratio. The first phase (food restriction) lasted 21days, and the following treatments were used: T0 (no artificial feed addition), T0.3, T0.6, T0.9, T1.2, T1.5, T1.8 and T2.1. In the second phase (re-feeding), the feeding rate was calculated based on the average of the best results in the first phase of the experiment (FCR=1.45). The re-feeding period lasted for more 29days. There were no observed significant differences in the water quality parameters among the treatments (P>0.05). At the end of the food restriction, the shrimp in T0, T0.3 and T0.6 presented lower final weights (P<0.05), and the weights in the other treatments did not significantly differ (P>0.05). The survival rate was lower only in T0 in the two phases of the study. The other treatments presented survival rates higher than 95%, with no significant differences among them. The feed intake did not increase during the re-feeding period, indicating that hyperphagia did not occur after a period of food restriction. The SGRs were higher for treatments that received lower amounts of feed in the first phase, and treatments T0, T0.3 and T0.6 presented partial weight compensation compared with the treatments with higher feeding rates. This study indicates that shrimp can be reared in a biofloc system with lower feeding rates, obtaining partial weight compensation and high survival rates and saving up to 24.79% of the artificial feed.