The suckling rat has provided a useful model for these studies of lipid digestion and absorption. In adults dietary triacylglycerols are predominantly hydrolyzed by the "classic" mechanism involving pancreatic lipase (E.C. 3.1.1.3) and biliary micelle-mediated product uptake. Unlike affluent man, adult laboratory rats normally consume a low-fat diet (< 20% of energy). However suckling rats, like most neonates, consume a milk diet that is normally high in fat. Suckling rats receive ~90% of non-protein energy from milk triacylglycerols, although rats have very low levels of "classic" pancreatic lipase before weaning. Dissertation studies demonstrate that other lipases promote efficient gastrointestinal triacylglycerol utilization in suckling rats. Nearly half of milk triacylglycerols are hydrolyzed to diacylglycerol within the stomach; and results strongly support that lingual lipase is the significant source of this activity. Furthermore, enzyme studies show considerable similarity between this lipase from rat tongue and so-called pregastric esterases of suckling ruminant species. Of fatty acids released in stomach, nearly three-quarters are of medium-chain length. These have high aqueous solubility and are rapidly absorbed from the upper gastrointestinal tract. Remaining triacylglycerols, diacylglycerols, and long-chain fatty acids enter the intestinal lumen and mix with lipid-rich bile. Suckling rats have higher biliary concentrations of bile salts, phospholipids and cholesterol than do adults. Bile salt enterohepatic circulation clearly occurs in the suckling rat, at least as early as 10 days. The bile acid β-muricholate is elevated during the suckling period, compared to post-weaning. Results show that further lipolysis occurs along the intestine, possibly through the action of lingual lipase and others from pancreas, producing mostly long-chain free fatty acids, monoacylglycerol, and some lysophosphatidylcholine, derived largely from bile. This composition closely resembles adult intestinal contents, but is much higher in both dietary and biliary lipid constituents. Alteration of milk triacylglycerol fatty acids produced no apparent impairment in gastrointestinal lipid utilization by sucklings, but resulted in hyperlipemia and increased carcass fatness. These results suggest gastrointestinal events do not limit triacylglycerol utilization in the suckling rat, regardless of composition; but post-absorptive metabolism may be different when sucklings consume altered milk lipids.

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Retrograded starches are commonly found in foods due to the production and/or processing conditions they have received prior to consumption. These resistant starches escape digestion in the small intestine and are fermented in the colon by the microflora present, to produce gases and SCFA in varying amounts. These are utilised by the host animal as an energy source, with a low gut pH being maintained by the production of SCFA. The fermentation of carbohydrates within the colon is beneficial to the health of the gut, as the beneficial bacterial species such as Lactobacillus and Bifidobacterium spp. are maintained, and a low pH reduces the activity of potentially harmful species such as the coliforms. The production of toxic metabolites from the breakdown of proteins will be reduced if these resistant starches persist further along the colon as a carbohydrate source. This is particularly important in the distal region of the colon, where the carbohydrate source usually becomes limited. The fermentation of both native and retrograded starches from various botanical sources containing varying amounts of the major components amylose and amylopectin, was examined. In particular, the effects on bacterial fermentation of variations in the ratios of amylose and amylopectin in starch, and of treatments such as retrogradation and/or pancreatin digestion was examined.

Orientador: Dalton José Carneiro / Banca: Marta Verardino de Stéfani / Banca: Ligia Maria Neira / Resumo: O Colossoma macropomum, comumente conhecido como tambaqui conquistou a posição de espécie nativa mais produzida na piscicultura, devido às boas condições zootécnicas com um bom padrão de crescimento e produtividade. Assim, a sua oferta no mercado consumidor se torna abundante. O hábito alimentar do tambaqui é onívoro-oportunista com preferências dietéticas que alterna do zooplâncton às sementes e frutas. Os peixes exigem diferentes nutrientes para manutenção de suas atividades fisiológicas normais. A adição de fontes de energia não proteicas tem melhorado a eficiência de retenção da proteína, incrementando a energia digestível disponível e também diminuindo as perdas metabólicas de nitrogênio. Proteína e energia assumem grande importância na composição de dietas para peixes, com maior destaque para a fração proteica, que é exigida em quantidades elevadas. A relação energia/proteína da dieta interfere de forma expressiva na determinação da concentração ótima de proteína em rações para peixes. O presente trabalho aplicado à nutrição de peixes apresenta dados de exigências proteicas e energéticas da espécie na fase inicial de crescimento. Forão realizados dois ensaios experimentais consecutivos. No primeiro foi estudado os coeficientes de digestibilidade dos 8 principais alimentos utilizados na formulação de dietas comerciais da espécie. E foi utilizado os resultados de digestibilidade na formulação das 8 dietas experimentais do segundo ensaio de desempenho produtivo. Utilizou-s... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Colossoma macropomum, commonly known as tambaqui, has gained the position of native species most produced in fish farming, due to the good zootechnical conditions with a good growth pattern and productivity. Thus, its offer in the consumer market becomes abundant. The tambaqui's eating habit is omnivorous-opportunistic with dietary preferences that alternate from zooplankton to seeds and fruits. Fish require different nutrients to maintain their normal physiological activities. The addition of non-protein energy sources has improved protein retention efficiency, increasing available digestible energy and also decreasing nitrogen metabolic losses. Protein and energy assume great importance in the composition of diets for fish, with greater emphasis on the protein fraction, which is required in high amounts. The energy / protein ratio of the diet significantly interferes in determining the optimal protein concentration in fish feed. The present work applied to fish nutrition presents data of protein and energy requirements of the species in the initial phase of growth. Two consecutive experimental trials are performed. In the first one, the digestibility coefficients of the 8 main foods used in the formulation of commercial diets were studied. And the digestibility results were used in the formulation of the 8 experimental diets of the second productive performance test. Eight treatments were used in a 4x2 factorial scheme, with extruded diets with four levels of digestible ene... (Complete abstract click electronic access below) / Mestre