Lack of affordable feeds is one of the major constraints facing small-scale fish farmers in Tanzania. This study evaluated the suitability of moringa leaf meal (MLM), cassava leaf meal (CLM) and cassava root meal (CRM) as novel ingredients in Nile tilapia, Oreochromis niloticus diets. Each of the ingredients was processed in an attempt to remove the most significant antinutritional factor. A series of five experiments was conducted in a recirculation system using juvenile O. niloticus. The fish were fed isonitrogenous (30g 100g-1), isolipidic (10g 100g-1) and isoenergetic (18 kJ g-1) diets containing graded levels of the processed ingredients to their apparent appetite but not exceeding 10% of their body weight for a period of 8 weeks. Processing led to the removal of 0.3% of saponin from MLM and 60% and 90% of hydrogen cyanide from CLM and CRM respectively. The contents of other inherent antinutritional factors such as phenols, tannins and phytic acid were little affected. Processed MLM, CLM and CRM had 31.1/29.0/1.5g 100g-1 of crude protein, 5.9/10.2/2.4g 100g-1 of crude fibre and 20.1/19.7/15.8k Jg-1 of gross energy. The content of sulphur amino acids was higher in CLM (0.47%) than in MLM (0.23%). Digestibe protein and digestible energy was higher in MLM (25.71g 100g-1/15.44kJ g-1) than in CLM (12.71g 100-1/9.16kJ g-1). CRM had a digestible energy content of 13.5kJ g-1. Inclusion of either of the leaf meals, even at the lowest level of 15g 100g-1 of total dietary protein, led to a significant reduction in feed intake, growth and feed utilisation. Liver and small intestine did not show any histopathological changes which could be linked to dietary treatment. Conversely, cassava root meal could replace up to 75% of wheat meal in the diet without significantly affecting performance. The performance of leaf meals was marginally improved by a combination of blending and feeding stimulants, whereby a blend containing 1 part MLM and 2 parts CLM could provide up to 20g 100g-1 of dietary protein without significantly reducing performance. Biological and economic performance of practical diets containing 30-50g 100g-1 of dietary protein from moringa and cassava blends (LMB) with feeding stimulants was significantly lower than a fishmeal-meal based diet (FM) but comparable to a soybean meal-based diet (SBM). The suitability of MLM and CLM as novel protein sources in O. niloticus diets will depend on 1) improving reduction/removal of inherent antinutritional factors in MLM and CLM as well as improving digestibility of CLM. On the other hand, the suitability of CRM as a carbohydrate energy source will depend on the availability of cost effective protein sources due to its low protein content.

Made available in DSpace on 2015-03-26T13:55:29Z (GMT). No. of bitstreams: 1 texto completo.pdf: 477916 bytes, checksum: 7f60ab95e78394c4ee61871a9c31bd74 (MD5) Previous issue date: 2007-03-19 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The current study was aimed at investigating the crude protein reduction and the methionine+cystine and threonine to lysine ratios, based on the ideal protein concept in diets for reverted Nile tilapia fingerlings (Oreochromis niloticus), of the thailand line. Four hundred twenty Nile tilapia fingerlings with an average initial weight of 1.83 ± 0.02 g, were allotted in a completely randomized design, with five treatments (seven replications per treatment and twelve fishes per experimental unit) in a 37-days trial. Treatment one consisted of a diet with 32.0% of crude protein (CP), methionine+ cystine:lysine ratio of 63.0% and threonine:lysine of 74.0%. In treatment two, the level of CP was reduced in four percentiles points and the amino acids ratios were the same of the treatment one, except the triptofan that was reduced in three percentiles points to ensure the minimum level of this amino acid. In treatment three the methionine+cystine:lysine ratio of 60.0% was used. In treatment four the methionine+ cystine:lysine ratio was 63.0% and the threonine:lysine ratio was 69.0%. The treatment five was similar to the treatment two, however was added 3.0% of glutamic acid, to verify a possible deficiency of nonessential amino acids. The fishes were maintained into 35 aquariums of 130 liters supplied with single-pass flow-through water, controlled temperature and indivudual aeration; and they were fed ad libitum six times per day. The fishes from treatment one had lower protein efficiency ratio and nitrogen efficiency ratio, whereas all the others parameters had no significant differences. The CP level of the diet is 28.0% since it is supplemented with limiting essential amino acids. The methionine+cystine and threonine to lysine ratios are 60.0% and 69.0%, respectively. / Objetivando-se avaliar a redução de proteína bruta e as relações dos aminoácidos metionina+cistina e treonina digestíveis com a lisina digestível, com base no conceito de proteina ideal, em rações para alevinos revertidos de tilápia do Nilo (Oreochromis niloticus), da linhagem tailandeza, foi realizado um experimento, com duração de 37 dias. Foram utilizados 420 alevinos, com peso inicial de 1,83 ± 0,02 g, distribuidos em delineamento inteiramente ao acaso, composto por cinco tratamentos, sete repetições por tratamento e doze peixes por unidade experimental. O tratamento um consistiu-se de uma dieta com 32,0% de proteína bruta (PB), relação de metionina+cistina com a lisina de 63,0% e de treonina:lisina de 74,0%. No tratamento dois, o nível de PB foi reduzido em quatro pontos percentuais e as relações aminoacídicas foram as mesmas do tratamento um, exceto do triptofano que foi reduzida em três pontos percentuais, garantindo-se o nível mínimo deste aminoácido. No tratamento três foi usada a relação da metionina+cistina com a lisina de 60,0%. No tratamento quatro a relação da metionina+cistina foi de 63,0% e a relação da treonina com a Lisina foi de 69,0%. O tratamento cinco foi constituído de uma ração semelhante a do tratamento dois, porém foi acrescentado 3,0% de ácido glutâmico, para verificar uma possível deficiência de aminoácidos não essenciais. Os peixes foram mantidos em 35 aquários de 130 litros dotados de abastecimento de água, temperatura controlada e aeração individual; e alimentados ad libitum em seis refeições diárias. O tratamento um proporcionou menores eficiência protéica para ganho e eficiência de retenção de nitrogênio, porém todos os outros parâmetros não tiveram diferenças significativas. O nível de PB da ração é de 28,0%, desde que seja suplementada com aminoácidos essenciais limitantes. As relações de metionina+cistina digestível e treonina digestível com a lisina são de 60,0% e 69,0%, respectivamente.