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 aspects such as when, where and how much to feed. Studies were conducted under pond conditions in order to determine the effects of feeding frequency on the grow-out patterns of Litopenaeus 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 m 2 each were installed in a 7.43-ha grow-out pond and stocked at 80 shrimp/m 2 (2.7 ± 1.52 g body weight). Shrimp were fed a commercial pelleted feed, delivered exclusively in feeding trays 2 (at 0700 and 1700 hours), 3 (at 0700, 1100 and 1500 hours), 4 (at 0700, 1000, 1300 and 1500 hours), 5 (at 0700, 0900, 1200, 1500 and 1700 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 from 39.58% to 34.07% and from 9.25% to 7.88%, respectively. Leaching of feed CP and lipid was not statistically different over the study period. Long feed water exposure generated significant losses in DM. Leaching of DM reached 4.65 ± 0.34% after the first hour of water immersion, peaking at 8 h (10.20 ± 0.48%). Shrimp were harvested at day 84 of grow-out, when average body weight ranged from 9.7 ± 1.75 to 10.9 ± 1.90 g. No shrimp performance benefit could be detected by adopting higher diurnal feeding frequencies. Although shrimp fed five times/day showed superior grow-out performance indices, at harvest no statistical differences were detected in shrimp survival (64.1 ± 11.7%), shrimp yield (0.46 ± 0.08 kg/m 2) and feed conversion ratio (2.85 ± 1.42) between feeding treatments. Also, no consistent growth pattern could be detected in relation to feeding treatments over the rearing cycle. The present study demonstrated that when feed rations are only adjusted at a weekly basis, using as the only criteria shrimp estimated biomass, delivering feed more than twice per day is not advantageous in the grow-out of L. vannamei.