Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

HIGH-DENSITY PELLET IMPROVES HOMOGENEITY AMONG JUVENILES TAMBAQUI Colossoma macropomum

Ana Beatriz de S. Farias* , Armando G. Prestes, Cláudia M. Epifânio, Driely K. M. Santos, César C. Oishi , Yugo M. Pastrana, Fernando Y. Yamamoto , Thaís B. Carvalho, Ligia U. Gonçalves

Thad Cochran National Warmwater Aquaculture Center

Mississippi State University

Stoneville, MS 38776

abd308@msstate.edu

 



 The aim of this study was to evaluate the influence of bulk density  of the pellet diet on feeding and aggressiveness , as well as the production  performance and homogeneity of the  batch of  tambaqui juveniles. To manufacture  the experimental diets, the  single screw  extruder settings were adjusted to produce pellets (equal diet formulation) with different bulk densities: high-density ( HD), medium-density (MD), and low-density (LD). The study was divided into three trials . Trial 1 : assessment of the physical quality of pellets: bulk density (BD), floatability (F), expansion (E), water solubility index (WSI), water absorvation index (WAI), pellet durability index (PDI), water stability (WS), and sinking velocity (SV) .  Trial 2: 48 fish were used to assess the aggressiveness of tambaqui juveniles when offered the experimental pellets. Fish were distributed in 12 aquariums (55L; n=4; 4 fish/aquarium) in a completely randomized design with three treatments (HD, MD, and LD ). For the behavioral interactions analysis, fish were recorded for 3 days, for  5 minutes after feeding, with a total of 360 minutes of observation. Ethograms of feeding behavior and aggressive interaction were elaborated and used to quantify the frequency of the respective behavioral units. To investigate the influence of bulk density on production performance (Trial 3),  225  tambaqui juveniles were equally distributed in 15 circular polyethylene tanks (260 L) , in a completely randomized design using  the same  dietary treatments (n=5, 15 fish/tank). Fish were fed four times a day  with 3% of biomass for 9 weeks .  In trial  1, all variables  were significantly affected by the density of the pellets , except for WSI and WAI. An inverse relationship between E and BD was observed,  in which p ellets with higher E presented lower BD. LD presented 75.33% of F , and pellets from MD and HD sank as soon as they reached  the water, with sinking velocity of 3.22 ± 0.40 and 7.37 ± 0.94 cm/s, respectively. PDI was  lower for LD diets, with 99.69 ± 0.03, due to the increase in E, which results in pellets with thinner walls and less resistance to mechanical stress. In trial  2, the  time of  feed consumption of fish fed LD was longer, totaling 8.7 ± 2.8 minutes. However, HD and MD were similar, with 0.2 ± 2.4 and 0.2 ± 3.9 min, respectively. It is likely that the physical characteristic of the LD of floating in  static water, demotivated fish to fed with the same motivation as the fish fed HD and MD, which immediately sa nk when reaching the  water. However, f ish fed MD presented higher aggressiveness  and social instability  in relation to  fish  fed HD and LD pellets . The longer period  that the  feed  pellets  stay in the water column, more competition is displayed by the tambaqui while feeding . Tambaqui from trial 3,  had higher feed intake  when  offered  HD and MD pellets  when  compared to the fish fed LD .  Despite  no significant differences were observed for  the weight gain data,  fish fed with HD presented lower variance in total weight (15.9 % of  the coefficient of variation ). HD pellet is suitable  for feeding tambaqui juveniles, resulting  in  a more stable social hierarchy with lower aggressiveness and  more homogeneous batch of fish.