Growth performance of the white shrimp Litopenaeus vannameireared under time- and rate-restriction feeding regimesin a controlled culture system

Abstract

When shrimp prices are low there can be economic pressure to restrict or cease feeding temporarily. Nevertheless, there is littleor no information available on the effects of moderate or severe feed restriction on growth performance ofLitopenaeus vannamei.The present study aimed at evaluating the effect of time- (TR) and rate-restricted feeding (RR) on the growth performance ofL.vannameiraised in controlled conditions. Three separate experiments were carried out in a clear water rearing system, composed of500-l tanks. In experiment 1, 2.8±1.20 g shrimp were stocked in 20 tanks at 46 shrimp/m2. Animals were randomly submitted tofour 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±1.44g shrimp were stocked in 16 tanks at 36 animals/m2and reared for 28 days. Shrimp in the control group were fed to satiation, whilein RR treatments feeding rates were reduced to 25%, 50% and 75%. In experiment 3, 9.1±1.95 g shrimp were stocked in eighttanks at 40 shrimp/m2. The experiment consisted of collecting feed remains at consecutive 1-h intervals, starting 1 h after first feeddelivery 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 TRperiods. Although survival was not affected by TR, yield and weekly growth were significantly higher for shrimp fed longer than 3h/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 toapparent satiation and with 25% restriction. In contrast, under the maximum RR (75%) shrimp showed the poorest feed efficiencyand development index (P<0.05). Shrimp feed intake was proportional to feed exposure and BW, not ration size. Feed intakeoccurred 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 feedintake. Also, this study has indicated it is possible to moderately reduce daily feeding rates without detrimental effects inL.vannameisurvival, growth and feed efficiency.