No abstract

Nile tilapia juveniles (8.35 ± 0.80 g) were fed on four levels (0.0%; 0.5%; 1.0%; 2.0%, 4.

This study evaluated the inclusion of Aurantiochytrium sp. (ALL-G-RICH ™ ), a source of docosahexaenoic acid (22:6 n-3, DHA), in the diet of Nile tilapia and its effect on growth performance indexes and body composition. Fish (initial mean weight 8.35 ± 0.80 g) were fed different dietary inclusion levels of ALL-G-RICH ™ : 0.00, 0.05, 0.10, 0.20, and 0.40 g/kg and a control diet using cod liver oil (CLO), to provide DHA content comparable to the inclusion of 0.10 g/kg ALL-G-RICH ™ . Although there was no significant effect (p > 0.05) on weight gain, specific growth rate, feed conversion, protein retention rate, and proximal body composition, the inclusion of ALL-G-RICH ™ in the Nile tilapia diet influenced positively the fatty acid profile in the body, resulting in a high DHA concentration. CLO-fed fish accumulated significantly more DHA compared to those fed 0.10 g/kg ALL-G-RICH ™ (p < 0.05). A digestibility trial was also performed for ALL-G-RICH with 65.86 g mean-initialweight fish. The digestibility was high for DHA (96.10%); however, it was low for palmitic acid (70.81%). The results show that the inclusion of up to 0.40 g/kg ALL-G-RICH ™ can be used in Nile tilapia diets without impairing growth performance.

Soy protein concentrate (SPC) was evaluated as a dietary replacement of animal protein sources (fish meal and poultry by-product meal) (APS) for juvenile Nile tilapia (Oreochromis niloticus). Apparent digestibility coefficients (ADC) of crude protein (CP) and dry matter (DM) were evaluated by feeding tilapia an experimental diet composed of 69.5% reference diet, 30% SPC, and 0.5% chromic oxide as inert marker. Apparent digestibility coefficients were 96.57% for CP and 76.84% for DM. In a feeding trial, increasing levels of dietary SPC (0, 33, 67, and 100%) replaced APS and were fed to tilapia juveniles (10.0 ± 0.18 g) for 60 days. Daily weight gain, specific growth rate, protein retention, feed conversion, body composition and liver histology were not significantly (P>0.05) affected by protein replacement. A second feeding trial compared tilapia's growth performance when SPC was supplemented with methionine and threonine (100% SPC+aa, 100% SPC, and 0% SPC) as well as CP and DM digestibility. The amino acid supplementation of SPC significantly increased tilapia daily weight gain. Diets containing 100%SPC and 100% SPC+aa promoted higher protein ADC values than diet containing only APS. However, DM ADC values were significantly higher in fish fed 0% SPC when compared to 100% SPC. Therefore, SPC can replace poultry by-product meal and fish meal in diets for Nile tilapia without compromising growth performance, protein retention, body composition, liver histology, and protein digestibility. However, SPC supplementation with limiting amino acids, such as methionine and threonine, is advisable since it further increases weight gain and protein digestibility. RESUMOConcentrado proteico de soja (CPS) foi avaliado como substituto dietético das farinhas de peixe e vísceras de aves (FP e FVA) para juvenis de tilápia do Nilo (Oreochromis niloticus). Os coeficientes de digestibilidade aparente (CDA) da proteína bruta (PB) e matéria seca (MS) foram avaliados com o fornecimento de dieta experimental composta de 69,5% da dieta referência, 30% CPS e 0,5% de óxido de cromo como marcador inerte. O CDA foi de 96,57% para PB e 76,84% para MS. Em ensaio de alimentação, dietas com níveis crescentes de CPS (0, 33, 67 e 100%) foram oferecidas para juvenis de tilápia (10,0 ± 0,18 g) por 60 dias. Ganho de peso diário, taxa de crescimento específico, retenção proteica, conversão alimentar, composição corporal e histologia hepática não foram afetados (P>0,05) pela substituição. Um segundo ensaio de alimentação comparou crescimento e digestibilidade quando CPS foi suplementado com metionina e treonina (100% CPS+aa, 100% CPS, e 0% CPS). A suplementação resultou em maior ganho de peso diário dos peixes. As dietas 100% e 100% CPS+aa promoveram maiores CDA para proteína que a dieta 0% CPS. No entanto, o CDA para MS foi significativamente maior nos peixes alimentados com 0% CPS quando comparado com 100% CPS. CPS pode substituir FP e FVA em dietas de tilápia do Nilo sem comprometer o desempenho do crescimento, retenção proteica, composição...