La diversification des productions aquacoles mono-spécifiques apparaît fondamentale pour assurer la pérennité des entreprises conchylicoles françaises, touchées pour une crise depuis 2008. Cette thèse bidisciplinaire est le résultat du suivi et de l’accompagnement scientifique et socio-technique réalisés auprès d’une TPE ostréicole de la Baie de Bourgneuf. Celle-ci ayant diversifié sa production d’huîtres par le co-élevage de l’oursin Paracentrotus lividus, elle rencontrait des problèmes sur le plan biologique, technique et organisationnel, d’où le recours à la recherche. Les objectifs de cet accompagnement étaient (1) d’optimiser la zootechnie de l’oursin en l’adaptant aux ressources disponibles par les professionnels ostréicoles ainsi que (2) d’identifier les appuis et freins à l’acceptabilité de l’activité par les consommateurs et les encadrants de la filière. Des tests sur l’alimentation et le recrutement des larves d’oursin ainsi que sur l’alimentation des adultes ont été réalisés. En parallèle, ont été organisés des rencontres auprès du réseau d’acteurs de la filière conchylicole. Ce réseau a été suivi grâce à la Sociologie de la Traduction pour étudier son rôle dans le déploiement de l’innovation. Il apparaît que l’oursin est un candidat potentiel pour diversifier l’ostréiculture dans la région et qu’il a une place à prendre sur le marché national. Cependant, des limites au développement d’une filière échinicole ont été trouvées sur le plan socio-économique : les moyens financiers font défaut et le soutien institutionnel nécessaire pour la réussite de l’innovation ne peut être déclenché que si les porteurs des projets s’engagent dans des dynamiques collectives. / The diversification of monospecific aquaculture production appears to be crucial to ensure the sustainability of French shellfish farming companies, which have been affected by a crisis since 2008. This bi-disciplinary thesis is the result of monitoring and offering scientific and socio-technical support to a small oyster farm from Bourgneuf Bay. This farm has diversified its oyster production by co-cultivating sea urchins Paracentrotus lividus but with substantial biological, technical and organizational problems. The objectives of this work were (1) to optimize the zootechnics of sea urchin culture by adapting it to the resources available to the oyster farmers and (2) to identify the support and obstacles to the acceptability of sea urchin farming by consumers and institutions. Feeding and recruitment tests of sea urchin larvae as well as adult feeding tests were carried out. Simultaneously, meetings were held with shellfish industry stakeholders. This networking was done according to the Actor-Network-Theory to study its role in the deployment of innovation. It appears that sea urchin farming is a good candidate for diversifying oyster farming in the region and that it can have a relevant place on the national market. However, some limits to the development of an echinoculture industry have been found at the socio-economic level: the financial resources are still lacking and the institutional support necessary for the success of the innovation can only be triggered if the project promoters work within collective dynamics.

ABSTRACT: The objective of this study was to evaluate the effect of Saccharomyces cerevisiae yeast supplementation on the senescent equine diet and its effect on performance and apparent nutrient digestibility coefficients. Eighteen castrated male horses, with no defined breed, with a mean weight of 426.167±25.3kg and mean age of 17.5±1.42 years were used. The treatments consisted in the use of different sources of yeasts added to 200g of concentrate, being: control treatment - without addition of yeast (10mL sterile culture medium); Treatment containing yeast Saccharomyces cerevisiae, UFMG 905 in the concentration at 3x108 CFU/mL/day; And treatment containing commercial probiotic composed of Lactobacillus casei >7.9x104CFU/mL, Lactobacillus acidophilus >7.9x104CFU/mL and Saccharomyces cerevisiae >1.5x106CFU/mL. The standard diet was composed of commercial concentrate and Tifton 85 hay (Cynodon spp) in the proportion of 30:70, respectively. The experiment lasted 31 days, with 28 days of adaptation and three days for the digestibility assay. The performance of the animals was evaluated by weight, concentrate feed intake, forage and total diet feed intake. For the determination of the digestibility coefficients, the total fecal collection method was used. The isolation of microorganisms Lactobacillus spp. direct plate counting was used. The design was completely randomized, with three treatments and six replicates, considering the animal the experimental unit. The data were analyzed by ANOVA and Dunnet test, considering 5% of significance for the performance variables and 10% for the digestibility coefficients. The final weight, concentrate feed intake, forage and total diet feed intake did not differ between treatments (P>0.05). However, there was an increase in weight (P=0.03) and higher weight gain (P=0.03) in animals supplemented with yeast UFMG 905. Organic matter, ethereal extract, neutral detergent fiber, acid detergent fiber and non-structural carbohydrates did not differ between treatments (P> 0.05). However, the digestibility coefficients of the dry matter (P=0.05) and the crude protein (P=0.10) were higher in the commercial treatment compared to the control treatment and for the hemicellulose the coefficient of digestibility was lower in the commercial treatment in relation to the control treatment, bacterial growth in UFMG905 and commercial treatments were similar to each other with elevation from 106 to 107cfu/g. In conclusion, probiotic supplementation with Saccharomyces cerevisiae in diets for horses older than 16 years increased weight gain, dry matter and crude protein digestibility, and favored a growth of Lactobacillus spp. could be used as a probiotic. More studies are needed to define optimal yeast concentrations and their effects on horses. / RESUMO: Objetivou-se avaliar o efeito da suplementação de levedura Saccharomyces cerevisiae na dieta de equinos senescentes e seus efeitos sobre o desempenho e coeficientes de digestibilidade aparente de nutrientes. Foram utilizados 18 equinos machos castrados, sem raça definida, com peso médio 426,167±25,3kg e idade média de 17,5±1,42 anos. Os tratamentos consistiram na utilização de diferentes fontes de leveduras adicionados a 200g de concentrado, sendo: tratamento controle - sem adição de levedura (10mL meio de cultura estéril); tratamento contendo a levedura Saccharomyces cerevisiae, UFMG 905 na concentração de 3x108 UFC/mL/dia; e o tratamento contendo probiótico comercial composto por Lactobacillus casei >7,9x104UFC/mL, Lactobacillus acidophilus >7,9x104UFC/mL e Saccharomyces cerevisiae >1,5x106UFC/mL. A dieta padrão foi composta por concentrado comercial e feno Tifton 85 (Cynodon spp) na proporção de 30:70, respectivamente. O experimento teve a duração de 31 dias, sendo 28 dias de adaptação e três dias para o ensaio de digestibilidade. Foi avaliado o desempenho dos animais por meio do peso, consumo de concentrado, de volumoso e da dieta total. Para determinação dos coeficientes de digestibilidade foi utilizado o método de coleta total de fezes. O isolamento de microrganismos Lactobacillus spp. usou-se a contagem direta em placas. O delineamento foi inteiramente casualizado, sendo três tratamentos e seis repetições, considerando o animal a unidade experimental. Os dados foram analisados por meio da ANOVA e teste Dunnet, considerando 5% de significância para as variáveis de desempenho e 10% para os coeficientes de digestibilidade. O peso final, consumo de concentrado, volumoso e dieta total não diferiram entre os tratamentos (P>0,05). Entretanto, houve aumento do peso (P=0,03) e maior ganho de peso (P=0,03) nos animais suplementados com a levedura UFMG 905. A matéria orgânica, extrato etéreo, fibra em detergente neutro, fibra em detergente ácido e teor de carboidratos não estruturais não diferiram entre os tratamentos (P>0,10). Entretanto, os coeficientes de digestibilidade da matéria seca (P=0,05) e da proteína bruta (P=0,10) foram maiores no tratamento comercial em relação ao controle e o coeficiente de digestibilidade da hemicelulose foi reduzido (P=0,01) no tratamento comercial em relação ao controle, o crescimento bacteriano nos tratamentos UFMG905 e comercial foram semelhantes entre si com elevação de 106 para 107 ufc/g. Em conclusão, a suplementação de probiótico contendo Saccharomyces cerevisiae em dietas para equinos acima de 16 anos, aumentou o ganho de peso, a digestibilidade da matéria seca e da proteína bruta e favoreceu um crescimento de Lactobacillus spp., podendo ser utilizado como probiótico. Mais estudos são necessários no sentido de definir concentrações ótimas de leveduras e seus efeitos em equinos. / São Cristóvão, SE