Utilização de glúten de trigo na alimentação de dourada, Sparus aurata (Linnaeus, 1758)

A incorporação de fontes proteicas alternativas à farinha de peixe na alimentação de espécies piscícolas tem sido objecto de variados estudos no âmbito da nutrição animal. Neste contexto realizou-se o presente trabalho, cujo objectivo foi determinar o nível de substituição ideal de farinha de peixe por glúten de trigo na alimentação de dourada. Foram realizados dois ensaios, um de crescimento e um de digestibilidade. O ensaio de crescimento efectuou-se para determinar qual o nível máximo de substituição sem que os animais apresentassem diferenças significativas em termos de taxa de crescimento. O ensaio de digestibilidade teve como principal objectivo determinar qual das dietas testadas proporcionaria melhores valores de utilização digestiva por parte dos animais. Tendo em conta os resultados dos ensaios e as condições experimentais em que se realizaram, verificou-se que a substituição até 40% não afecta significativamente o desempenho zootécnico das douradas. ABSTRACT; The incorporation of alternative protein sources in fish diets has been the aim of many scientific experiments in animal nutrition. ln this study, the main objective was to evaluate the ideal level of wheat gluten incorporation in substitution of fishmeal in diets for gilthead sea bream (Sparus aurata L). To reach this objective, two experiments were carried out, in which growth and digestibility were studied. The aim of the growth experiment was to evaluate the maximum level of fish meal substitution by wheat gluten (20%, 40%, 60% and 80%), without affecting significantly the animals growth rate. The digestibility experiment took place to evaluate which animals presented better food utilization with the tested diets (20%, 40%, 60% and 80%). Observing the results of these two experiments, it was concluded that the substitution until 40% did not affect significantly the performance of the fishes.

Tannins in Ruminant Nutrition: Impact on Animal Performance and Quality of Edible Products

Tannins are widespread throughout the plant kingdom, occurring as hydrolysable and condensed tannins and at different levels in several animal feeding sources. Recent years have seen an increasing interest in the use of tannin-rich plants and plant extracts in ruminant diets for improving the quality of their edible products. Some results show that this strategy is effective in improving the fatty acid profile of meat and milk, increasing the level of health-beneficial fatty acids as well as enhancing the oxidative stability of the products. However, the use of tannin-rich feed in animal diets requires great care, due to its possible detrimental effects on animal performance and induction of metabolic disorders. Although promising, the results of studies on the effects of tannins on animal performance and quality of their products are still controversial, probably depending on type and chemical structure of tannins, amount ingested, composition of diet, and species of animal. In this chapter, the current knowledge regarding the effect of dietary tannins on animal performance and the quality of their products (meat and milk), particularly on the fatty acid profile, oxidative stability, and organoleptic properties, is reviewed. The tannin chemistry diversity and its occurrence in ruminant diets, as well as its beneficial and adverse effects on ruminants, will be briefly reviewed, and aspects related to oral cavity physiology, saliva production/composition, and postingestive effects will also be discussed.