Les mycotoxines telles que la fumonisine B1 (FB1) produites par les champignons du genre Fusarium sont particulièrement préoccupantes pour la filière maïsicole. L’ensilage de maïs est un processus de fermentation naturel susceptible de favoriser l’évolution des teneurs en FB1. La maîtrise du risque de contamination par la FB1 et la recherche de moyens permettant la décontamination des ensilages est donc nécessaire. L’objectif de ce travail est de caractériser le devenir de la FB1 dans les ensilages de maïs grain et de mettre en évidence l’existence d’agents microbiens capables de dégrader cette toxine. Pour cela, des mini-silos contenant du maïs grain naturellement contaminé en FB1 provenant de différents parcelles et issus des deux années de récolte ont été préparés. La stratégie analytique basée sur le dosage de la FB1 libre et la FB1 complexée par HPLC-MS/MS a révélé une diminution significative de la teneur en FB1 totale qui ne peut être attribuée à un mécanisme de complexation et résulte d’un mécanisme de dégradation. La recherche du microbiote associé à la dégradation de la FB1 a été réalisée par deux approches complémentaires : Une analyse métagénomique combinant l’extraction sélective de l’ADN microbien et le séquençage haut débit «shotgun» afin de comparer la diversité taxonomique et fonctionnelle d’un ensilage dégradant la FB1 et d’un ensilage moins dégradant. En parallèle, un criblage de microorganismes cultivables capables de métaboliser la FB1 a été conduit et a permis de confirmer les résultats de l’analyse globale. Ce travail apporte une première image du microbiote potentiellement associé à la dégradation de la FB1, ainsi que des activités microbiennes responsables. / Fungi of the genus Fusarium are one of the major contaminants of maize that can produce mycotoxins, such as the fumonisin B1 (FB1). Maize silage which is based on the fermentation of whole crop plant or grains is considered the main source of monogastrics and cattle feeding in Europe. The ensiling process could favor changes in FB1 content; however this has scarcely been documented. This led to questioning regarding the possibility of managing the microbiota during ensiling in order to reduce the level of mycotoxins exposure and improve feed quality. The aim of this work is to study the fate of FB1 during ensiling process of high moisture maize grain and to identify an endemic microbiota capable of degrading FB1. Laboratory scale silages were prepared with naturally contaminated FB1 grains from two cropping years. An analytical procedure allowed assessing both free and matrix associated FB1 forms and showed a significant decrease in total FB1 content that are not linked to the presence of bound FB1. Additionally, our data showed that the FB1 content decrease was mainly due to a degradation process. Identification of a potential microbiota responsible for FB1 degradation was conducted. A metagenomics approach combining a selective microbial DNA extraction and high-throughput shotgun sequencing showed microbial specific patterns between FB1 degrading and weakly degrading silage. These results were also supported by the isolation of microbial strains able to metabolize FB1. Ultimately, this work evidenced a microbiota associated to FB1 degradation and the functional diversity involved in this activity. Bacteria and yeasts have been obtained for further studies on degradation activities and their usage as silage starter.

Les Escherichia coli producteurs de Shiga-Toxines (STEC) sont responsables de maladies humaines sévères. Les ruminants sont considérés comme étant leur principal réservoir. La dissémination des STEC au sein des élevages est liée en partie à l’alimentation des animaux et donc potentiellement à l’ingestion d’ensilages contaminés. Les bactéries lactiques peuvent être employées comme agents technologiques ou dans des stratégies de bio-protection. Sur le plan de l’ensilage, elles jouent un rôle de préservation mais peuvent également représenter une barrière à la survie de pathogènes comme les STEC. Ce travail a permis de sélectionner des bactéries lactiques inhibitrices de la croissance de divers sérogroupes de STEC. Les études de compétitions ont mis en évidence un phénomène bactéricide sur certaines souches, dont le mécanisme reste encore non élucidé. Le potentiel inhibiteur des bactéries lactiques sélectionnées a été testé indépendamment dans des ensilages de maïs contaminés à différentes étapes de leur réalisation : à la mise en silos, à l’ouverture ou après une période d’exposition aérobie. En cas de contamination à la mise en silos, les souches de STEC testées n’ont pas survécu dans des ensilages correctement menés. Une souche de Ln. mesenteroides a permis de limiter la survie des souches de STEC dans les ensilages contaminés à l’ouverture. Cependant, après 144h d’aération, aucun additif n’a montré d’effet protecteur avéré. Le contrôle de l’alimentation animale afin de limiter l’entrée des STEC dans le cycle épidémiologique pourrait donc passer par l’emploi de bactéries lactiques ; sans négliger cependant les Bonnes Pratiques nécessaires à la réalisation de l’ensilage. / Shiga-toxin producing Escherichia coli (STEC) are responsible for severe human diseases. Cattle are considered as the main reservoir of this pathogen. STEC dissemination in farm environment is linked to cattle feed and potentially to ingestion of contaminated silage. Lactic Acid Bacteria (LAB) could be employed as starters in fermentations or in strategies of bioprotection. In silage, LAB play a preservative role and could also represent a barrier for the survival of pathogenic bacteria such as STEC. The selection of LAB strains, able to inhibit the growth of several serogroups of STEC strains, was performed in this study. Competitions assays have shown a bactericidal effect on some STEC strains, but reasons of this phenomenon remain unclear. Inhibiting potential of the selected LAB strains was tested independently in corn silages contaminated at different steps of their realizations : at ensiling, at opening or after aerobic exposure. In case of contamination at ensiling, STEC strains tested did not survive in well-made silages. A Ln. mesenteroides strain allowed the limitation of the STEC strains survival in silage contaminated at opening. However, after 144 h of aerobic exposure, no inoculant showed any protective effect. Control of cattle feed, in order to limit STEC entry in their epidemiological cycle, could be reached through LAB utilization ; however, Good Manufacturing Practices involved in silage making should not be omitted.

Made available in DSpace on 2014-06-11T19:33:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-30Bitstream added on 2014-06-13T18:45:25Z : No. of bitstreams: 1 rodrigues_jfh_dr_jabo.pdf: 490090 bytes, checksum: 16cb8217591247e91ae9d1757dc47d28 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Objetivou-se avaliar o efeito de aditivos químicos e dos períodos de exposição ao ar sobre as características nutricionais, microbiológicas das silagens pré secadas e dos fenos, bem como as características fermentativas das silagens de Tifton 85 (Cynodon spp.) colhidos em diferentes épocas do ano. Confeccionaram-se três silagens pré secadas com 50 a 60 % de matéria seca: não aditivada; aditivada com ácido propiônico tamponado e aditivada com uréia. Nos fenos, avaliaram-se os seguintes tratamentos: feno de alta umidade não aditivado; feno de alta umidade aditivado com uréia; feno de alta umidade aditivado com ácido propiônico tamponado e feno controle. Após o armazenamento das silagens pré secadas e dos fenos em condições anaeróbia, foram colhidas amostras no dia da abertura (tempo zero), quinto e nono dias após exposição aeróbia. O delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições, em parcelas subdivididas no tempo, sendo tratamentos, fatores das parcelas e tempo das subparcelas. A silagem aditivada com uréia apresentou maiores teores de PB (P < 0,05) em relação às demais silagens, no momento de abertura dos silos e no quinto dia de exposição aeróbia. Estimaram-se na silagem não aditivada, maiores valores de matéria seca, fibra em detergente ácido e lignina. O uso de aditivo alterou a composição nutricional das silagens, bem como a exposição ao ar. Houve efeito dos aditivos nas características de pH e nitrogênio amoniacal/NT e de aditivos e tempo na contagem de leveduras, entretanto não se verificou interação entre os dois fatores. A silagem aditivada com uréia apresentou valor superior de pH em relação a silagem aditivada com ácido propiônico. Maiores teores de nitrogênio amoniacal/NT foram verificados na silagem aditivada com uréia em comparação as demais silagens. As silagens aditivadas... / This study aimed to evaluate the effect of chemical additives and air exposition periods on the chemical composition, microbial population, and fermentation characteristics of the haylage and hay of the Tifton 85 (Cynodon spp.) harvested in different seasons of the year. Three wilted silages were prepared with 50-60% dry matter (DM), the first without additive (SE), the second treated with buffered propionic acid (SEAP) and the third with urea (SEU). In the hays the following treatments were evaluated: high-moisture hay without additive; high moisture hay with urea, highmoisture hay with buffered propionic acid, and control hay. After storage of the haylage and hay in anaerobic conditions, samples were taken on opening day (time zero) and at five days and nine days of aerobic exposition. The urea and propionic acid were applied, 1.0% of wet base on the haylage and hay. Experimental design was completely randomized with four replications in split plot scheme, considering treatments the factors of the parcels, and time on sub parcels. The SEU showed higher levels of CP (P <0.05), compared to other treatments, at the time of opening of the silos, and in the fifth day of aerobic exposition. It was estimated in the SE, the highest values (P <0.05) of DM, ADF and lignin, and lowest OM after nine days of aerobic exposition. Additive utilization change (P < 0.05) haylage chemical, as well as air exposition time. Significant effects of additives in the pH and N-NH3/NT characteristics was observed, and also the additives and air exposition effect in the yeast count (P <0.05), however there was no interaction (P> 0.05) between these factors. The SEU presented higher pH value compared to SEAP. Higher amounts of N-NH3/NT (P <0.05) were observed in the SEU related to other haylages. The SEU and SEAP showed lower yeast count compared to control haylage, it was observed also higher yeast... (Complete abstract click electronic access below)

Orientador: Sérgio Hugo Benez / Banca: Kléber Pereira Lanças / Banca: Antonio Renan Berchol da Silva / Resumo: Este trabalho teve como objetivo avaliar o consumo energético das operações mecanizadas envolvidas na produção de silagem de planta inteira e grão úmido de milho, tendo como referência o processamento seco deste cereal cultivado em sistema de plantio direto. O ensaio foi conduzido no ano agrícola 2005/2006, na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas - UNESP, localizada no município de Botucatu - SP, na região centro oeste do Estado de São Paulo. O processo de ensilagem foi conduzido na mesma fazenda experimental, nas instalações pertencentes à Faculdade de Medicina Veterinária e Zootecnia - UNESP - Campus de Botucatu-SP. Os tratamentos foram relacionados a época de colheita da cultura do milho, e foram divididos da seguinte forma: silagem de planta inteira (cento e treze dias após a emergência), silagem de grão úmido (cento e quarenta e sete dias após a emergência) e colheita de grãos secos (cento e setenta dias após a emergência). No experimento, o delineamento experimental foi em blocos ao acaso com parcelas subdivididas no tempo (três épocas de colheita: silagem de planta inteira, silagem de grãos úmidos e colheita de grãos secos), com 10 repetições. Cada parcela experimental possuía 50 m de comprimento e 10 m de largura, perfazendo área de 500 mø. As análises estatísticas foram realizadas através do programa ESTAT, pelo teste de média de Tukey a 5 % de probabilidade. A silagem de planta inteira teve o maior consumo de combustível por área, mas permite o produtor antecipar em 63 dias o plantio e desenvolvimento da cultura sucessora e a maximização da utilização da terra mesmo em condições edafoclimáticas desfavoráveis em razão da distribuição irregular de precipitação. A secagem dos grãos de 15,5 % para 13% foi responsável por 87% do gasto de energia por área. A silagem de grão úmido demandou... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work aims to evaluate the energy consumption of the mechanized operations involved in silage production of entire plant and humid maize, having as reference the dry processing of this cereal cultivated in no tillage. The trial was carried out in agricultural year 2005/2006, on Lageado Experimental Farm of the Agronomy School, UNESP, in Botucatu, in the center western region of the State of São Paulo, Brazil. The ensilage process was lead on the Education Research and Production Farm, of the Veterinary School of - UNESP - Botucatu Campus, Brazil. The treatments are related to the harvest time of the maize, and divided as follows: ensilage of the entire plant (one hundred and thirteen days after emergence), ensilage of humid grain (one hundred and forty and seven days after emergence) and harvest of dry grains (one hundred and seventy days after emergence). In the trial, the experimental design was in bands with parts subdivided in time (three times of harvest: silage of entire plant, silage of humid grains and harvest of dry grains), with 10 repetitions. Each experimental unit was 50m long and 10m wide, amounting to 500 m ø. The statistical analyses were performed with ESTAT software, and Tukey test at 5% of probability. The plant silage completes had the largest consumption of fuel for area, but it allows the producer to advance even in 63 days the planting and the culture successor's development and the best use of the use of the earth in conditions unfavorable climatic in reason of the irregular distribution of precipitation. The drying of the grains of 15,5% for 13% was responsible for 87% of the expense of energy for area. The silage of... (Complete abstract, click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:22:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-21Bitstream added on 2014-06-13T19:07:49Z : No. of bitstreams: 1 bueno_rj_me_jabo.pdf: 638842 bytes, checksum: 94a9fe6127820ecd17460806e354c604 (MD5) / Universidade Estadual Paulista (UNESP) / Este trabalho teve como objetivo avaliar o efeito da silagem ácida de resíduos da filetagem de tilápias em dietas do piauçu Leporinus macrocephalus. Foram utilizados 300 alevinos de piauçu com três faixas de pesos (2,0-2,5g; 2,51- 3,0g; 3,01-3,5g), distribuídos em 30 aquários de 100 litros de volume útil. O delineamento utilizado foi em blocos casualizados com duas repetições por bloco. Os peixes foram alimentados até a saciedade sem que houvesse sobras, duas vezes ao dia com dietas isoproteicas (32% PB) e isoenergéticas (4150kcal/kg EB). Foram empregados cinco tratamentos sendo: 0%, 2%, 4%, 6% e 8% de inclusão de silagem ácida de resíduos de filetagem de tilápias nas dietas. Durante todo o experimento a qualidade da água foi mantida em condições ideais para um bom desenvolvimento da espécie. Foram avaliados os parâmetros de desempenho, composição corporal, eficiência de utilização de nutrientes, índice hepato-somático e índice gordura-víscero-somático. Após 84 dias, os resultados mostraram que não ocorreram diferenças significativas sobre nenhum dos parâmetros avaliados (P>0,05), indicando que a inclusão de até 8% de silagem ácida de resíduos de filetagem de tilápias na dieta de alevinos de piauçu não causou prejuízo no crescimento, saúde e qualidade da carcaça. / This work aimed to evaluate the effect of acid ensilage of tilapia filleting residues on diets for piauçu Leporinus macrocephalus. It was used 300 piauçu fry with three weight ranges (2.0-2.5g; 2.51-3.0g; 3.01-3.5g), distributed in 30 aquaria with 100 liters of useful volume. The design used was randomized blocks with two replicates each block. Fish were fed until satiation with no leftovers, twice a day with isoproteic (32% CP) and isoenergetic (4150kcal/kg GE) diets. Five treatments were applied: 0%, 2%, 4%, 6% and 8% of tilapia filleting residues acid ensilage inclusion on the diets. During all the experiment, water quality was maintained under ideal conditions for the species good development. Parameters of performance, body composition, nutrient utilization efficiency, hepato-somatic index and mesenteric fat index were evaluated. After 84 days, results have shown no significant differences for any of the tested treatments (P>0.05), indicating that the inclusion of up to 8% of tilapia filleting residues acid ensilage on diets for piauçu fry has caused no damage on growth, health or carcass quality.

Made available in DSpace on 2014-06-11T19:24:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-01-19Bitstream added on 2014-06-13T18:52:22Z : No. of bitstreams: 1 seki_as_me_botfca.pdf: 830350 bytes, checksum: 84d18e5dc80a042138334b8a72a5291f (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho teve como objetivo avaliar o consumo energético das operações mecanizadas envolvidas na produção de silagem de planta inteira e grão úmido de milho, tendo como referência o processamento seco deste cereal cultivado em sistema de plantio direto. O ensaio foi conduzido no ano agrícola 2005/2006, na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas - UNESP, localizada no município de Botucatu - SP, na região centro oeste do Estado de São Paulo. O processo de ensilagem foi conduzido na mesma fazenda experimental, nas instalações pertencentes à Faculdade de Medicina Veterinária e Zootecnia - UNESP - Campus de Botucatu-SP. Os tratamentos foram relacionados a época de colheita da cultura do milho, e foram divididos da seguinte forma: silagem de planta inteira (cento e treze dias após a emergência), silagem de grão úmido (cento e quarenta e sete dias após a emergência) e colheita de grãos secos (cento e setenta dias após a emergência). No experimento, o delineamento experimental foi em blocos ao acaso com parcelas subdivididas no tempo (três épocas de colheita: silagem de planta inteira, silagem de grãos úmidos e colheita de grãos secos), com 10 repetições. Cada parcela experimental possuía 50 m de comprimento e 10 m de largura, perfazendo área de 500 mø. As análises estatísticas foram realizadas através do programa ESTAT, pelo teste de média de Tukey a 5 % de probabilidade. A silagem de planta inteira teve o maior consumo de combustível por área, mas permite o produtor antecipar em 63 dias o plantio e desenvolvimento da cultura sucessora e a maximização da utilização da terra mesmo em condições edafoclimáticas desfavoráveis em razão da distribuição irregular de precipitação. A secagem dos grãos de 15,5 % para 13% foi responsável por 87% do gasto de energia por área. A silagem de grão úmido demandou... / This work aims to evaluate the energy consumption of the mechanized operations involved in silage production of entire plant and humid maize, having as reference the dry processing of this cereal cultivated in no tillage. The trial was carried out in agricultural year 2005/2006, on Lageado Experimental Farm of the Agronomy School, UNESP, in Botucatu, in the center western region of the State of São Paulo, Brazil. The ensilage process was lead on the Education Research and Production Farm, of the Veterinary School of - UNESP - Botucatu Campus, Brazil. The treatments are related to the harvest time of the maize, and divided as follows: ensilage of the entire plant (one hundred and thirteen days after emergence), ensilage of humid grain (one hundred and forty and seven days after emergence) and harvest of dry grains (one hundred and seventy days after emergence). In the trial, the experimental design was in bands with parts subdivided in time (three times of harvest: silage of entire plant, silage of humid grains and harvest of dry grains), with 10 repetitions. Each experimental unit was 50m long and 10m wide, amounting to 500 m ø. The statistical analyses were performed with ESTAT software, and Tukey test at 5% of probability. The plant silage completes had the largest consumption of fuel for area, but it allows the producer to advance even in 63 days the planting and the culture successor's development and the best use of the use of the earth in conditions unfavorable climatic in reason of the irregular distribution of precipitation. The drying of the grains of 15,5% for 13% was responsible for 87% of the expense of energy for area. The silage of... (Complete abstract, click electronic access below)

Made available in DSpace on 2015-03-26T13:55:08Z (GMT). No. of bitstreams: 1 texto completo.pdf: 337392 bytes, checksum: fe191b2d9ab148e2398deaa665aca657 (MD5) Previous issue date: 2006-10-02 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Two experiments were conducted to evaluate the nutritive value, the profile of fermentation of sorghum silage produced with addition urea doses and two storage periods and to determine nitrogen and carbohydrates fractions of the silages. The PVC silos with 50 cm of height and 10 cm of diameter were used to sorghum storage. In the experiment I, the evaluation of the nutritional value of the silages was accomplished through the determination of the chemical composition and in vitro dry matter disappearance (IVDMD) of the silages and, the fermentation profile, through the determination of the contents of ammonia-N, values pH and WSC of the silages. The urea addition in the production of the sorghum silage was shown with potential of minimizing losses of DM of the silage. The urea addition in the sorghum ensilage increased the contents of CP, NDIP and the IVDMD of the silages and it reduced the contents of NDF, ADF, cellulose and lignin. The storage period had effect on the contents of NDF, ADF, cellulose and lignin. In relation to the inherent variables to the fermentative characteristics of the silages, the urea doses had quadratic effect on the contents of ammonia-N of the silages. The values of pH of the silages increased lineary. There was effect of the storage periods on the contents ammonia-N and pH value. There was interaction between urea doses and storage period, only on the pH value. However, the urea addition in the sorghum ensilage did not damage fermentation profile of silages and it can improve his nutritive value. In the experiment II, crude protein and CT fractions of the silages were determined and evaluated. The nitrogen fractions of the silages were influenced by the urea addition, being verified positive lineal effect for the contents of the A fraction, negative lineal effect for B1+B2, B3 and C fractions. The regression analysis detected lineal reduction of the contents of CT in function of the urea addition. The fractions of CT were influenced by the urea addition, being verified negative lineal effect on the contents of the A+B1 fraction, positive lineal effect about the B2 fraction and positive lineal effect for the content of the C fraction inside of the period of 60 days. / Dois experimentos foram conduzidos no delineamento inteiramente casualizado para avaliar o valor nutritivo, o perfil de fermentação de silagem de sorgo produzida com a adição de doses crescentes de uréia e dois períodos de armazenamento e determinar as frações protéicas e dos carboidratos da silagem. Foram usados silos de PVC com 50 cm de altura e 10 cm de diâmetro para o armazenamento do sorgo. No experimento I, a avaliação do valor nutritivo das silagens foi realizada através da determinação da composição química e da digestibilidade in vitro da matéria seca das silagens e, o perfil de fermentação, através da determinação dos teores de nitrogênio amoniacal, dos valores de pH e dos teores de carboidratos solúveis (CHOS) das silagens. A adição de uréia na produção da silagem de sorgo mostrou-se com potencial de minimizar perdas de matéria seca (MS) da silagem. A adição de uréia na ensilagem de sorgo aumentou os teores de proteína bruta (PB), proteína insolúvel em detergente neutro (PIDN), digestibilidade in vitro da matéria seca (DIVMS) das silagens e diminuiu os teores de fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), celulose e lignina. O período de armazenamento teve efeito sobre os teores de FDN, FDA, celulose e lignina. Em relação às variáveis inerentes às características fermentativas das silagens, as doses de uréia tiveram efeito quadrático sobre o teor de nitrogênio amoniacal das silagens. Os valores de pH das silagens aumentaram linearmente. Houve efeito significativo dos períodos de armazenamento sobre o teor de nitrogênio amoniacal e valor de pH. Houve efeito de interação entre doses de uréia e período de armazenamento, apenas sobre o valor de pH. Entretanto, a adição de uréia na ensilagem de sorgo não prejudicou o perfil de fermentação das silagens e pode melhorar o valor nutritivo das mesmas. No experimento II, foram determinadas e avaliadas as frações que constituem a PB e os carboidratos totais (CHO) das silagens. As frações nitrogenadas (A, B1+B2, B3 e C) das silagens foram influenciadas pela adição de uréia, constatando-se efeito linear positivo para os teores da fração A, efeito linear negativo para as frações B1+B2, B3 e C. A análise de regressão detectou redução linear do teor de CHO em função da adição de uréia. As frações de CHO (A+B1, B2 e C) foram influenciadas pela adição de uréia, constatando-se efeito linear negativo sobre os teores da fração A+B1, efeito linear positivo sobre a fração B2 e efeito linear positivo para o teor da fração C dentro do período de 60 dias.

Orientador: Ruben Pablo Schocken-Iturrino / Banca: Hélio José Montassier / Banca: Alessandra Aparecida Medeiros / Resumo: Visando suplementar ruminantes no período seco, a cana-de-açúcar nos últimos anos tem sido bastante pesquisada e empregada como volumoso alternativo, principalmente na forma de silagem. Na ensilagem desta forrageira, principalmente quando utilizada após queima do canavial, ocorre uma alta atividade de leveduras epífitas que convertem os carboidratos solúveis da forragem em etanol, gás carbônico e água, levando a elevadas perdas de matéria seca, aumento no teor de fibra em detergente neutro e diminuição de consumo. Buscando amenizar esses problemas temse pesquisado inoculantes bacterianos compostos por bactérias ácido-produtoras, tais como o Lactobacillus buchneri. Sendo assim, objetivando avaliar os efeitos antimicrobianos e químicos na silagem de cana-de-açúcar queimada e inoculada com Lactobacillus buchneri, quatro silos de superfície foram analisados por meio dos seguintes tratamentos: cana-de-açúcar crua sem aditivo; cana-de-açúcar crua inoculada com L. buchneri; cana-de-açúcar queimada sem aditivo e cana-de-açúcar queimada e inoculada com L. buchneri. As amostragens foram efetuadas após 0, 21, 49, 77 e 105 dias de utilização dos silos, sendo retiradas do centro e superfície do painel. Houve redução na população de leveduras e fungos filamentosos nas silagens inoculadas e aumento nas queimadas. Constatou-se maior população de microrganismos na camada superficial, além de maiores valores de pH e nitrogênio amoniacal. Ocorreram menores perdas de matéria seca na silagem de cana-de-açúcar queimada e inoculada em relação ao seu controle. As silagens apresentaram os fungos filamentosos Aspergillus, Penicillium, Trichoderma, Rhizopus e Neurospora após abertura, verificando-se redução na frequência dos mesmos ao longo do período. O inoculante exerceu um efeito redutor na população de leveduras e na perda de MS sendo esse efeito potencializado pela... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In order to supplement ruminants's diets in dry period, sugarcane in the last years has been researched and processed as silage to used as an alternative food. In this ensilage process, mainly after sugar cane plantation have been set on fire, occurs a high activity of yeasts that convert the soluble carbohydrates of the forage in ethanol, carbon dioxide and water, leading to dry matter losses, increase in fiber content and decrease in the intake. In a way to solve those problems bacterial inoculants produced with acid-producers bacteria's, such as Lactobacillus buchneri, have been researched. Considering this the aim of the present study was to evaluate the microbiological and chemical effects on burned sugarcane silage when inoculated with Lactobacillus buchneri. Four silos type surface were analyzed using the following treatments: sugarcane without additives; sugarcane inoculated with L. buchneri; burned sugarcane without additives; and burned sugarcane inoculated with L. buchneri. The samples were taken after 0, 21, 49, 77 and 105 days after opening the silos and they were taken from the center and the surface of the panel. There was a reduction in the population of yeasts and filamentous fungi in inoculated silages and an increase of them in burned silages. There was a greater population of microorganisms in the superficial layer, in addition to higher pH values and ammoniacal nitrogen. The burned silage inoculated with L. buchneri showed the least amount of losses of dry matter in comparison to the control sample. The fungi Aspergillus, Penicillium, Trichoderma, Rhizopus and Neospora were found in the silages after opening the silos and the frequency of these microorganisms decreased with the passing of time. The inoculating had an reduccing effect in the yeast's population and in the loss of DM, and this effect was enhanced by the burn of the sugarcane... (Complete abstract click electronic access below) / Mestre

La sélection génomique offre de nouvelles perspectives en amélioration des plantes pour la sélection de caractères complexes. Le travail proposé porte sur l’évaluation de son intérêt dans le cadre d’un programme de sélection réciproque pour la valeur d’hybrides entre deux groupes génétiques de maïs complémentaires. Il s’appuie sur un dispositif expérimental original constitué de 900 hybrides produits dans un plan factoriel entre deux dispositifs multiparentaux connectés. L’objectif de la sélection est d’améliorer le rendement ensilage des hybrides tout en améliorant leur digestibilité. Une réflexion sur les modèles permettant de prédire la valeur hybride sera conduite et testée sur les données expérimentales et par simulations. Ce travail, conduit en collaboration avec sept sociétés de sélection (au sein de PROMAÏS) devrait permettre d’améliorer les dispositifs de sélection classiques et de produire des hybrides d’intérêt agronomique. Il s’inscrit dans le cadre plus général de l’amélioration pour la valeur en croisement commune à de nombreuses espèces végétales allogames et à certaines espèces animales. / Genomic selection opens new prospects in plant breeding for the selection of complex traits. The proposed study aims to evaluate its efficiency in the context of a reciprocal selection schemes for the hybrid value between two complementary maize groups. The work will rely on an original experimental design including 900 hybrids produced from a factorial between two multiparental connected designs. The selection objective is to increase the hybrids silage yield as well as their digestibility. Several models for the hybrid value prediction will be proposed and tested on the experimental data and by simulations. This study, carried out in close connection with seven plant breeding companies (members of PROMAÏS) will contribute to the improvement of breeding designs and will produce new interesting hybrids. It falls within the general context of the selection for hybrid value which is common to numerous plant allogamous species and animal species.

Le maïs (Zea mays L.) est la plante la plus cultivée au monde. Pour valoriser le fort effet d’hétérosis pour les caractères liés à la biomasse, la diversité génétique du maïs est structurée en groupes hétérotiques et les variétés cultivées sont majoritairement des hybrides F1 entre lignées de groupes complémentaires. La valeur hybride se décompose comme la somme de l’Aptitude Générale à la Combinaison (AGC) de chacune des lignées parentales et de l’Aptitude Spécifique à la Combinaison (ASC) du couple. En Europe du Nord, le maïs est souvent utilisé en ensilage destiné à l'alimentation animale. L’objectif de sélection est d’améliorer la productivité et d'assurer une bonne digestibilité du maïs ensilage. Les objectifs de cette thèse étaient : (i) d’estimer l’importance de l’AGC et de l’ASC dans la variance génétique hybride pour les caractères de qualité de l’ensilage, (ii) d’identifier les locus (QTL) impliqués dans ces caractères et d’étudier leur colocalisation avec des QTL de productivité, (iii) d’évaluer l’intérêt de la sélection génomique pour la prédiction des performances hybrides et (iv) de comparer l’efficacité de deux dispositifs de calibration des prédictions basés sur un factoriel ou l’utilisation classique de testeurs du groupe complémentaire. Dans le cadre du projet SAM-MCR, 6 familles biparentales connectées ont été créés dans les groupes « corné » et « denté » à partir de 4 lignées fondatrices. Dans une première phase, 822 lignées cornées et 802 dentées ont été génotypées pour 20k SNP et croisées selon un factoriel incomplet pour produire 951 hybrides, phénotypés pour des caractères de qualité et de productivité (étudiés par H. Giraud pendant sa thèse). L’analyse des caractères de qualité a montré une prédominance de l’AGC par rapport à l’ASC ainsi qu’une corrélation négative entre les caractères de qualité et le rendement. De nombreux QTLs multi-alléliques ont été détectés, la plupart spécifiques d’un groupe et dont certains colocalisent avec des QTL de rendement. Par validation croisée, la qualité de prédictions basées sur les QTL détectés s’est avérée plus faible que celle obtenue par prédiction génomique. La prise en compte de l’ASC n‘a pas permis d’améliorer sensiblement la qualité de prédictions des modèles. Dans une seconde phase, 90 lignées ont été choisies par groupe : 30 sélectionnées sur la base de leurs prédictions génomiques pour la productivité et la valeur énergétique et 60 choisies aléatoirement parmi les 6 familles. Ces lignées ont été croisées selon un factoriel incomplet pour produire 360 nouveaux hybrides : 120 issus des lignées sélectionnées et 240 issus des lignées choisies au hasard. Les 90 lignées de chaque groupe ont aussi été croisées à deux lignées fondatrices du groupe complémentaire (testeurs). Les hybrides issus des lignées sélectionnées se sont avérés plus productifs mais de moins bonne qualité. Nous avons confirmé la bonne qualité des prédictions génomiques obtenus dans le factoriel initial sur les nouveaux hybrides évalués dans d’autres environnements et après sélection et observé une bonne corrélation entre les AGC estimées dans le factoriel et dans le dispositif testeurs. Des dispositifs factoriels et testeurs ont été simulés en faisant varier la part d’ASC, le nombre d’hybrides et la contribution de chaque lignée dans le jeu de calibration. A moyens expérimentaux égaux, le dispositif factoriel s’est avéré plus efficace en termes de capacité prédictive et de gain génétique cumulé que le dispositif testeur (jusqu’à +50%) pour un caractère présentant de l’ASC et équivalent pour un caractère purement additif. Les résultats de cette thèse ouvrent de nouvelles perspectives pour revisiter les schémas de sélection hybrides en remplaçant l’évaluation des lignées candidates, classiquement faite sur testeur, par l’évaluation directe d’hybrides issus d’un factoriel incomplet. La mise en œuvre de tels dispositifs nécessitera de réorganiser la logistique des programmes de sélection. / Maize (Zea mays L.) is the most cultivated crop in the world. To exploit the strong heterosis for traits related to biomass, the genetic diversity of maize is structured into heterotic groups and cultivated varieties are mainly F1 hybrids obtained by crossing lines from complementary groups. The hybrid value can be decomposed as the sum of the General Combining Ability (GCA) of each parental line and the Specific Combining Ability (ASC) of the cross. In northern Europe, maize is often used as silage for animal feed and the breeding objective is to improve productivity while ensuring a good energetic value and digestibility of the silage. The objectives of this thesis were: (i) to estimate the importance of GCA and SCA in hybrid genetic variance for silage quality traits, (ii) to identify loci (QTL) involved in these traits and to study their colocalization with QTL for productivity traits, (iii) to evaluate the interest of genomic selection for the prediction of hybrid performances and (iv) to compare the prediction accuracies of two calibration designs either based on a factorial or on the conventional use of testers from the complementary group. As part of the SAM-MCR project, 6 biparental connected families were created in the "flint" and "dent" groups from 4 founder lines. In a first phase, 822 flint and 802 dent lines were genotyped for 20k SNPs and crossed according to an incomplete factorial to produce 951 hybrids which were phenotyped for quality traits and for productivity traits (studied by H. Giraud during her phD). Quality trait analysis showed a predominance of GCA over SCA and a negative correlation between digestibility traits and silage yield. Several multi-allelic QTLs were detected, most of them being specific to one group. Several colocalizations were found with yield QTL. Using cross-validation, we observed that the predictive ability of models based on detected QTLs was lower than that obtained by genomic predictions. Considering the SCA did not improve model predictive abilities for most of the traits. In a second phase, 90 lines were chosen per group: 30 were selected based on their genomic predictions for productivity and the energetic value and 60 were randomly sampled from the 6 families. These lines were crossed according to an incomplete factorial to produce 360 new hybrids: 120 from selected lines and 240 from randomly chosen lines. The 90 lines of each group were also crossed to two lines of the complementary group (testers). Hybrids from the selected lines were more productive but had a lower silage quality. We confirmed the good accuracy of the genomic predictions obtained in the initial factorial on the new hybrids evaluated in other environments and after selection. We also observed good correlations between GCA estimated in the factorial and in the testcross design. Different factorial and testcross designs were simulated by varying the proportion of dominance/SCA, the number of hybrids and the contribution of each line to the calibration set. Considering the same number of hybrids in the calibration set, the factorial was more efficient in terms of predictive ability and cumulative genetic gain (up to + 50%) than the testcross design for traits showing SCA and was similar for purely additive traits. The results of this thesis open new perspectives to revisit hybrid breeding schemes by replacing the evaluation of candidate lines, classically made on testcross, by the direct evaluation of hybrids resulting from an incomplete factorial. The implementation of such designs will require reorganizing the logistics of selection programs.