Effects of feeding frequency on feed leaching loss and grow-out patterns of the white shrimp Litopenaeus vannamei fed under a diurnal feeding regime in pond enclosures

Abstract

Feed management plays a major role in the economical and environmental status of shrimp farms. It involves basic aspectssuch as when, where and how much to feed. Studies were conducted under pond conditions in order to determine the effectsof feeding frequency on the grow-out patterns ofLitopenaeus vannamei. Feed loss of crude protein (CP), lipid and dry matter(DM) over different water exposure periods were also investigated. In a commercial shrimp farm, 25 open-bottom enclosures(5 treatments and 5 replicates) of 50 m2each were installed in a 7.43-ha grow-out pond and stocked at 80 shrimp/m2(2.7F1.52 g body weight). Shrimp were fed a commercial pelleted feed, delivered exclusively in feeding trays 2 (at 0700 and1700 hours), 3 (at 0700, 1100 and 1500 hours), 4 (at 0700, 1000, 1300 and 1500 hours), 5 (at 0700, 0900, 1200, 1500 and1700 hours) and 6 times/day (at 0700, 0900, 1100, 1300, 1500 and 1700 hours). Feed was made available over continuous 24-h periods and remains were collected at next feeding. After 8 h of water immersion, feed CP and lipid level dropped from39.58% to 34.07% and from 9.25% to 7.88%, respectively. Leaching of feed CP and lipid was not statistically different overthe study period. Long feed water exposure generated significant losses in DM. Leaching of DM reached 4.65F0.34% afterthe first hour of water immersion, peaking at 8 h (10.20F0.48%). Shrimp were harvested at day 84 of grow-out, whenaverage body weight ranged from 9.7F1.75 to 10.9F1.90 g. No shrimp performance benefit could be detected by adoptinghigher diurnal feeding frequencies. Although shrimp fed five times/day showed superior grow-out performance indices, atharvest no statistical differences were detected in shrimp survival (64.1F11.7%), shrimp yield (0.46F0.08 kg/m2) and feedconversion ratio (2.85F1.42) between feeding treatments. Also, no consistent growth pattern could be detected in relation tofeeding treatments over the rearing cycle. The present study demonstrated that when feed rations are only adjusted at a weeklybasis, using as the only criteria shrimp estimated biomass, delivering feed more than twice per day is not advantageous in thegrow-out ofL. vanname