Growth performance of the white shrimp Litopenaeus vannamei reared under time- and rate-restriction feeding regimes in a controlled culture system

Abstract

When shrimp prices are low there can be economic pressure to restrict or cease feeding temporarily. Nevertheless, there is little or no information available on the effects of moderate or severe feed restriction on growth performance of Litopenaeus vannamei. The present study aimed at evaluating the effect of time- (TR) and rate-restricted feeding (RR) on the growth performance of L. vannamei raised in controlled conditions. Three separate experiments were carried out in a clear water rearing system, composed of 500-l tanks. In experiment 1, 2.8 ± 1.20 g shrimp were stocked in 20 tanks at 46 shrimp/m 2. Animals were randomly submitted to four experimental treatments (2, 3, 4, 5 h/day of feed availability) and one control (6 h/day) for 96 days. In experiment 2, 9.1 ± 1.44 g shrimp were stocked in 16 tanks at 36 animals/m 2 and reared for 28 days. Shrimp in the control group were fed to satiation, while in RR treatments feeding rates were reduced to 25%, 50% and 75%. In experiment 3, 9.1 ± 1.95 g shrimp were stocked in eight tanks at 40 shrimp/m 2. The experiment consisted of collecting feed remains at consecutive 1-h intervals, starting 1 h after first feed delivery up to 8 h. Treatments were composed of 9 replicates, each with an uninterrupted observation period of 9 days. In all trials, shrimp were fed a 39.6% crude protein diet delivered in PVC feeding trays. Shrimp performed better in treatments under longer TR periods. Although survival was not affected by TR, yield and weekly growth were significantly higher for shrimp fed longer than 3 h/day. There were no statistical differences in BW when shrimp were fed to apparent satiation versus under a 25% and 50% RR ( P > 0.05). On the other hand, final BW of shrimp fed at 75% restriction was significantly lower ( P < 0.05) than that of shrimp fed to apparent satiation and with 25% restriction. In contrast, under the maximum RR (75%) shrimp showed the poorest feed efficiency and development index ( P < 0.05). Shrimp feed intake was proportional to feed exposure and BW, not ration size. Feed intake occurred in a continuous and uniform fashion over the 8-h feed exposure period. On average, hourly feed intake reached 4.09% BW. The present study has shown that longer and continuous feed exposure periods enhanced shrimp growth performance and feed intake. Also, this study has indicated it is possible to moderately reduce daily feeding rates without detrimental effects in L. vannamei survival, growth and feed efficiency.