Modelagem matemática da proteína digestível e determinação da digestibilidade da proteína e aminoácidos em ingredientes de origem vegetal para tilápias

• Ano de defesa: 2012
• Autor(a) principal: Vidal, Luiz Vítor Oliveira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual de Maringá; Brasil; Programa de Pós-Graduação em Zootecnia; UEM; Maringá, PR; Centro de Ciências Agrárias
• Palavras-chave em Português: Tilápias; Nutrição; Avaliação de alimentos; Modelagem matemática; Estimativa; Nutriente limitante; Validação; Brasil.; Tilapia; Nutrition; Food assessment; Mathematical modeling; Estimate; Limiting nutrient; Validation; Brazil.; Ciências Agrárias; Zootecnia
• Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/1588

In three studies the mathematical modeling was used as a tool for evaluating the digestibility of plant ingredients for tilapia and the relationships between digestible nutrients and nutritional requirements of the species. In the first, digestible protein (DP),apparent digestibility coefficient of crude protein (ADCCP), crude protein, crude fiber, ether extract and mineral matter of biological assays obtained from the literature were subjected to multiple linear regression and path analysis, to all ingredients and subgroups, as seeds and byproducts as well as alternative ingredients. The models were validated by independent data also obtained in the literature. In the second, mathematical models adjusted to estimate the digestible protein ingredients for various fish species were evaluated, as well as various feed groups to check their applicability to plant ingredients, provided to the tilapia in extruded diets. In the third study, the apparent digestibility of protein and amino acids were evaluated, as well as the correlation between these values. The digestible amino acids content of the ingredients were compared with the nutritional requirement of the species as a function of digestible protein. For the second and third studies juvenile Nile tilapia weighing 30.38 ± 4.52 were used, fed with a practical extruded diet, with chromium III (Cr2O3) oxide as an indicator of digestibility. The system used for feces collection was adapted from Guelph. Fish were fed to satiation six times, between 11h and 16h, with the placement of the collector tubes at 17h for the stool sedimentation overnight and later collection at08h. In the first study path analysis estimated the crude protein as the most influential independent variable on the digestible protein, independent of separation into subgroups. Less than half of the ADCCP variation is explained by the variation of the chemical composition. The model for seeds and byproducts was the best among the adjusted models: it uses only one independent variable to estimate the digestible protein of the ingredients, showed high accuracy coefficients and the individual null hypothesis accepted, in this way, the estimated values do correspond to observed values. In the second study, none of the models had the null hypothesis accepted, either individual or paired. However, it was observed that models adjusted for more restricted feed groups were more efficient, so the two models adjusted for seeds and byproducts had the estimated values closer to the observed DP, especially the model adjusted for indistinct species. In the third study, the apparent digestibility coefficients were high for all ingredients, being the lowest ones for the crude fiber-rich ingredients, in the corn and wheat groups. The apparent digestibility of crude protein and amino acids showed high correlation with a determination coefficient of 100% in the three groups. Although deficient in certain amino acids, the wheat group was more balanced with respect to providing the nutritional requirements of the species, a fact confirmed by the Euclidean distance, calculated in the Hierarchical Cluster Analysis. The group of soybean, although not as close to the nutritional requirements of the species, appears to be quite useful for formulation, because it shows an excess of some amino acids, such as lysine. This compensates the deficiency of other important feeds in diet formulation for fish, such as the corn group.