Granulometria dos ingredientes para uso em ração extrusada na qualidade física dos péletes e desempenho zootécnico de tambaqui (Colossoma macropomum)

Abstract

The particle size of feedstuff can interfere on the physicochemical parameters during the aquafeed extrusion process, influencing the pellet physical quality and, consequently, in the nutrients utilization by the fish. Therefore, the present study aimed to evaluate different particle size of ingredients in the physical quality of pellets of extruded feed and its impact on the zootechnical performance of tambaqui (Colossoma macropomum Cuvier, 1818) juveniles. Three experimental diets were produced with the same formulation, with different particle sizes of the ingredients: 500; 700 and 1000 μm. The pellets of the experimental diets were extruded in a 3 mm die and analyzed for moisture, apparent density, buoyancy, expansion rate, water solubility index, water absorption index, durability index of the pellets, water resistance and scanning electron microscopy. For the zootechnical performance experiment, 375 tambaqui juveniles (31.18 ± 0.27 g) were housed in 15 experimental tanks (1000L) at the density of 25 fish per experimental unit, in a completely randomized design composed of three diets (different particle size of feedstuff: 500; 700 and 1000 μm) and five replicates each. Fish were fed four times a day (8:00, 11:00, 14:00, 17:00 h) until apparent satiety for 56 days. Zootechnical parameters: feed intake, crude protein intake, protein efficiency rate, apparent feed conversion, weight gain, daily weight gain, final weight, final length, relative growth rate, condition factor and survival were evaluated. The results of the physical tests of the feed pellets with different granulometry particle size of the ingredients differed significantly (p<0.05) for moisture, apparent density, buoyancy, water absorption index, water solubility index and water resistance. And all the feed pellets presented the same expansion rate and durability index of the pellets. For the zootechnical performance, the results show that there were no significant difference (p<0.05) for feed intake, crude protein intake, protein efficiency rate, feed conversion rate, weight gain, daily weight gain, final weight, final length, relative growth rate, condition factor and survival. Biometric index (viscerosomatic, hepatosomatic and viscerosomatic fat indices) also showed no statistical difference (p>0.05). Furthermore, there were similarity between the results, which may have contributed to the same growth performance of tambaqui juveniles. This can be attributed to an average size of the particles of the ingredients that have been subjected to the different grindings. It is recommended the production of extruded feed from ground ingredients with particle size of 1000 μm for tambaqui juveniles for presenting lower cost in grinding processing.