Efeito da granulometria de rações sobre o desempenho zootécnico de juvenis do camarão Litopenaeus Vannamei

Abstract

In shrimp farming, feeds have a cylindrical shape, varying their diameter and length in response to the gain in shrimp body weight during culture. It is suggested that pellets with a smaller particle size result in a greater distribution of food among the cultured population, and, therefore, provides better growth performance and homogeneous body weight in farmed shrimp. The present study evaluated the effect of different pellet sizes on the growth performance of juvenile of the white shrimp, Litopenaeus vannamei. Three feeds were lab-manufactured with the following variations in pellet diameter and length: 1.33 ± 0.14 and 4.76 ± 1.23 mm; 2.23 ± 0.28 and 4.73 ± 0.66 mm; and, 2.92 ± 0.08 and 4.03 ± 0.52 mm, respectively. Shrimp of 8.45 ± 1.31 g were stored at 61 shrimp/m2 (34 shrimp per tank) were cultured for 45 days in ten clear-water tanks of 0.5 m3 with continuous water recirculation. Shrimp were fed four times daily exclusively in feeding trays. Experimental diets showed no difference in final moisture content (7.83 ± 0.39%) and physical water stability (82.47 ± 5.91%). However, feed hardness increased proportionally with an increase in pellet diameter, from a minimum of 0.83 ± 0.29 to a maximum of 3.60 ± 0.87 kg. No significant differences were observed between the experimental diets in regards to shrimp final survival (100 ± < 0.0001%), final body weight (17.38 ± 2.40 g), weekly growth (1.39 ± 0.09 g), gained yield (535 ± 39 g/m2 ), apparent feed intake (15.5 ± 0.3 g/shrimp) and feed conversion ratio (1.75 ± 0.16). At the end of the study period, shrimp body weight coefficient of variation (cv) fed diets 1.33 x 4.76 mm (diameter x length) and 2.23 x 4.73 mm decreased from 16.6 and 14.5% to 11.8 and 11.1%, respectively. On the other hand, cv of shrimp fed the 2.92 x 4.03 mm diet increased from 14.9 to 18.2%. This study found that juvenile L. vannamei with a body weight ranging from 8.5 and 17.4 g can be fed diets between 1.33 and 2.92 mm diameter without deleterious effects on their growth performance. Pellets with a diameter between 1.33 and 2.23 mm produce shrimps with a more homogeneous body weight than pellets of 2.92 mm.