Aquaculture represents a sustainable alternative to natural fisheries for provision of high quality, animal protein. Crustaceans make a significant contribution to global aquaculture production, of which decapods are the most economically important group. Among freshwater crayfish, the genus Cherax includes several species that have emerged as important culture species. A suite of favourable biological attributes, including fast growth and an omnivorous feeding habit, have contributed to establishment of successful culture of Cherax quadricarinatus (redclaw) in many countries. Aspects of redclaw production, however, remain relatively undeveloped, in particular feed formulation. To better understand the digestive processes and nutritional requirements of redclaw, this study examined the relationship between diet composition and digestive enzyme activity, growth performance and diet digestibility coefficients. The extent to which redclaw can efficiently utilise complex polysaccharides, such as cellulose, has been speculated on by authors who reported endogenous cellulase activity in this species. I evaluated the use of insoluble α-cellulose by redclaw, demonstrated that high dietary levels (30%) can significantly reduce the specific activity of selected digestive enzymes (amylase and cellulase), while also lowering apparent digestibility coefficients. Inclusion of α-cellulose above 12% also significantly reduced survival rate, specific growth rate and feeding efficiency in this organism which corresponds with low tolerance for insoluble fibre by other decapods. Even though redclaw possess endogenous cellulases, they appear to have only a limited capacity to utilise insoluble fibre in their diets. Further, I assessed the impact of different nutrient profiles on digestive enzyme activity, growth and tail muscle composition in redclaw. Purified diets containing varying levels of dietary protein significantly affected activity of digestive enzymes (protease, amylase and cellulase) and the composition of the tail muscle tissue. Redclaw have a relatively low protein requirement, which was reflected here, as little significant difference was observed in growth rates and the feed conversion ratio was only significantly affected by the lowest protein diet. Manipulation of the non-protein energy component in purified diets (protein to lipid ratio) had no effect on growth performance indices in redclaw. Digestive enzyme activity (protease) was however, strongly influenced by both the amount of protein and lipid in the diet and a significant correlation was observed between protease activity and growth performance indices. The findings here, provide preliminary data for consideration of digestive enzymes such as proteases as potential growth indicators for freshwater crayfish. These enzymes are already recognised as reliable biological indicators for comparison of digestive efficiency and potential growth rate in fish. The relationship between diet composition and digestive enzyme expression observed here, stress the need for further empirical evaluation of specific ingredients in artificial diets for redclaw. A range of single cell, plant and animal-based, agricultural products were assessed for their potential use in diets formulated for redclaw. Analysis of dietary supplements revealed that apparent digestibility of crude protein was generally higher for diets containing plant-based ingredients. A similar outcome was observed for digestibility coefficients of test ingredients. Ingredient type also had a significant effect on digestive enzyme activity. Importantly, a significant correlation was observed for enzyme activity and apparent digestibility coefficients. It appears that redclaw have the capacity to utilise nutrients from a broad range of dietary ingredients successfully including animal, single cell and in particular, plant matter in their diet. Taken together, the results presented here demonstrate that digestive enzyme activities in redclaw are significantly influenced by diet composition. I show clearly that the ability of redclaw to utilise various nutrients (measured as digestibility coefficients) is highly correlated with digestive enzyme activity. Finally, protease activity demonstrated a potential for use as an indicator of redclaw growth performance. The data presented here will contribute to development of better and cheaper feed formulations for use in redclaw aquaculture and have broader applications to freshwater crustacean culture. In particular, the potential for use of plant-based ingredients in aqua-feeds for redclaw will contribute to a more economically and environmentally sustainable redclaw culture.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The objective of this experiment was to evaluate the effect of diet with high grain diets on the carcass tissue composition, the centesimal composition and the profile of the fatty acids deposited in the meat of Lambs finished in confinement, as well as the economical viability of the system. Thirty - eight male lambs, castrated, of the Texel breed, born of simple birth and weaned at approximately 50 days of age, were used. The treatments were constituted by different types of grains, unprocessed, being: corn grain, white oat grain, black oat grain or rice grain with bark. The animals were slaughtered when they reached the pre-established slaughter weight of 32 kg, which corresponds to 60% of the adult weight of their mothers. The lambs of the different treatments presented similarity as to the proportion of muscle. However, corn-based treatment lambs presented lower percentage of bone and higher amount of fat. Considering the cholesterol variable, the animals treated with black oats presented results lower than 90mg / 100g, and human health could be considered healthy in this approach. Grouping the fatty acids evaluated by degree of saturation, corn-based treatment lambs had the lowest results when compared to the others, but when evaluating these lipids individually, the animals of this treatment contained the highest proportion of fatty acids Undesirable when compared to treatments based on white oats, shelled rice or black oats. The polyunsaturated: saturated ratio also presented superior results for the lambs fed the corn grain diet when compared to the others. In order to evaluate the economic issue, consecutive historical quotations from 2003 to 2016 were considered. The univariate analysis was characterized by a completely randomized design, with four treatments and eight replications. The multivariate analysis consisted of clustering. By the univariate analysis, the only treatment that proved advantageous was the corn grain base, where values were found for gross margin of R $ 16.55; Net margin of R $ 10.45; Profit of R $ 12.59; Net present value of R $ 11.44; Benefit index: cost of 1.05; Additional return on investment of 2.4% a.m.; Internal rate of return of 3.3% a.m. and discounted payback of 1.91 months. By cluster analysis, corn treatment was also the one that presented the greatest discrepancy in relation to the other treatments, while the treatments based on white oats and black oats were the ones that presented the closest ones. Thus, meat from lambs confined to a high-fat diet, because it presents results close to those recommended for healthy consumption, can be ingested without risk to consumers, since human food consists not only of sheep meat but must be nutritionally balanced. The joint analysis of the financial indicators indicated the feasibility of the confinement of lambs with a high grain diet only for the treatment based on corn grain, determining economic unviability in this study for the other evaluated treatments. / O presente experimento, conduzido no Laboratório de Ovinocultura da Universidade Federal de Santa Maria, teve como objetivo avaliar o efeito da alimentação com dietas de alto grão, sobre a composição tecidual da carcaça, a composição centesimal e o perfil dos ácidos graxos depositados na carne de cordeiros terminados em confinamento, bem como a viabilidade econômica do sistema. Foram utilizados 32 cordeiros machos, castrados, da raça Texel, nascidos de parto simples e desmamados com aproximadamente 50 dias de idade. Os tratamentos foram constituídos por diferentes tipos de grãos, não processados, sendo: grão de milho, grão de aveia branca, grão de aveia preta ou grão de arroz com casca. Os animais foram abatidos quando atingiram o peso vivo de abate pré-estabelecido de 32 kg, que corresponde a 60% do peso adulto de suas mães. Os cordeiros dos diferentes tratamentos apresentaram similaridade quanto a proporção de músculo. Porém, os cordeiros do tratamento a base de grão de milho apresentaram menor percentagem de osso e superior quantidade de gordura. Já considerando a variável colesterol os animais tratados com aveia preta apresentaram resultados inferiores a 90mg/100g, podendo ser considerado salutar a saúde humana nesta abordagem. Agrupando os ácidos graxos avaliados por grau de saturação, os cordeiros do tratamento a base de grão de milho apresentaram os menores resultados quando comparados aos demais, mas ao avaliar individualmente estes lipídios contatou-se que os animais desse tratamento continham a maior proporção de ácidos graxos não desejáveis quando comparado aqueles dos tratamentos a base de aveia branca, arroz com casca ou aveia preta. A relação poliinsaturado:saturado também apresentou resultados superiores para os cordeiros alimentados com a dieta a base de grão de milho quando comparado aos demais. Para avaliar a questão econômica foram consideradas cotações históricas consecutivas dos anos de 2003 a 2016. A análise univariada caracterizou-se por delineamento inteiramente casualizado, com quatro tratamentos e oito repetições. A análise multivariada consistiu em agrupamento (cluster). Pela análise univariada, o único tratamento que se mostrou vantajoso foi o a base de grão de milho, onde foram encontrados valores para margem bruta de R$ 16,55; margem líquida de R$ 10,45; lucro de R$ 12,59; valor presente líquido de R$ 11,44; índice benefício:custo de 1,05; retorno adicional sobre o investimento de 2,4% a.m.; taxa interna de retorno de 3,3% a.m. e payback descontado de 1,91 meses. Pela análise de cluster, o tratamento a base de milho também foi o que apresentou maior discrepância em relação aos demais tratamentos, enquanto que os tratamentos a base de aveia branca e aveia preta foram os que se apresentaram mais próximos. Assim a carne proveniente de cordeiros confinados com dieta de alto grão, por apresentar resultados próximos aos preconizados para o consumo salutar, pode ser ingerida sem proporcionar risco aos consumidores, uma vez que a alimentação humana não consiste apenas em carne ovina devendo ser nutricionalmente balanceada. A análise conjunta dos indicadores financeiros indicou viabilidade do confinamento de cordeiros com dieta de alto grão somente para o tratamento a base de grão de milho, determinando inviabilidade econômica neste estudo para os demais tratamentos avaliados.

Traditionally, fish meal (FM) and fish oil (FO) have been used extensively in aquafeeds, mainly due to their excellent nutritional properties. However, various reasons dictate the use of sustainable alternatives and the reduction of the dependence on these commodities in fish feeds. Hence, the aim of the present thesis was to investigate the effects of the replacement of FM and FO with two vegetable oils (VO) and an oilseed meal on the growth performance, feed utilization, nutrient and fatty acids (FA) digestibility and tissue FA composition and metabolism in three commercially important European fish species. Specifically, in Experiment I crude palm oil (PO) was used to replace FO in diets for rainbow trout. In Experiments II and III FO was replaced with rapeseed oil (RO) in diets for Atlantic salmon at various dietary protein/lipid levels aiming also at further reductions of FM by using low protein (high lipid) diet formulations. In Experiments II and III the fish were reared at low and high water temperatures, respectively, in order to elucidate, also, the potential effects of temperature. Lastly, the effects of the replacement of FM with full fat soya meal (FFS) in Atlantic cod were investigated in Experiment IV. The results of the present thesis showed no negative effects on growth performance and feed utilization in rainbow trout when FO was replaced with PO. The dietary inclusion of RO improved the growth of Atlantic salmon, possibly, due to changes in the nutrient and FA digestibilities and FA catabolism while, the growth and feed utilization were unaffected by the dietary protein/lipid level. However, the growth of Atlantic cod was affected negatively by the replacement of FM with FFS. The proximate composition of the fish whole body was in most cases unaffected by dietary treatments. The changes in dietary formulations affected the dietary FA compositions and resulted in significant changes in the fish tissue FA compositions. It was clearly shown that the fish tissue total lipid FA composition reflects the FA composition of the diet, although specific FA were selectively utilized or retained in the tissues by the fish. These may have serious implications not only for fish metabolism and growth but also for the quality of the final product, especially in terms of possible reductions of n-3 HUFA.