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Made available in DSpace on 2014-12-17T15:34:49Z (GMT). No. of bitstreams: 1 LeonardoSF_DISSERT.pdf: 1030836 bytes, checksum: a6b397303645ae7aef050c0d9c4ee9c6 (MD5) Previous issue date: 2014-02-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The low quality of tropical pastures in the dry season justifies the use of dietary supplements to meet the nutritional needs of sheep to meat production. Therefore, the objective of this experiment was to evaluate the agronomic characteristics of massaigrass in the dry season and the effect of protein supplements in the performance and productivity of sheep to meat production grazing. The protein supplements evaluated were: soybean meal, Leucena hay, Gliricidia hay and multiple mixture. The animals were managed in massaigrass pastures under rotational stocking and supplemented daily. Were used 24 sheep ? Santa In?s x ? SPRD (without defined breed), males uncastrated, mean age 90 days in a completely randomized design. Performance of sheep was evaluated for average daily gain of live weight gain per area and stocking rate (animals of 25 kg/ha). The pasture was evaluated for forage mass of pre and post-grazing, the percentages of participation of morphological constituents and their nutritional values and rates of herbage accumulation. The total herbage mass decreased throughout the dry season. Crude protein and in vitro digestibility of organic matter of the leaf were higher in the upper 15 cm of the canopy stratum. The average daily weight gain of the animals supplemented with legume hay was similar to that gained by animals supplemented with soybean meal in the four grazing cycles. The total live weight gain of animals supplemented with legume hay was higher than the animals supplemented only with multiple mixing the first two grazing cycles. Hays of Leucena and Gliricidia can be given for supplementation of sheep maintained on pasture / A baixa qualidade dos pastos tropicais na esta??o de seca justifica o uso de suplementos alimentares para atender as necessidades nutricionais dos ovinos de corte. Assim, objetivou-se com este experimento avaliar suplementos proteicos para produ??o de ovinos de corte em pastejo e seu efeito nas caracter?sticas do pasto de capim-massai. Os tratamentos constitu?ram dos suplementos proteicos farelo de soja, feno de Leucena, feno de Gliric?dia e mistura m?ltipla. Os animais foram manejados em pastos de capim-massai sob lota??o intermitente e suplementados diariamente. Foram utilizados 24 ovinos ? Santa In?s x ? SPRD (sem padr?o racial definido), machos n?o castrados, com idade m?dia de 90 dias em delineamento inteiramente casualizado. Foi avaliado o desempenho dos ovinos quanto ao ganho de peso vivo m?dio di?rio, ganho por ?rea e a taxa de lota??o (animais de 25 kg/ha). O pasto foi avaliado quanto ? massa de forragem total no pr? e p?s-pastejo e quantificada as massas dos constituintes morfol?gicos, o valor nutritivo e as taxas de ac?mulo de forragem. A massa de forragem total diminuiu ao longo da esta??o seca. Teores de prote?na bruta e digestibilidade in vitro da mat?ria org?nica da l?mina foliar foram superiores no estrato superior a 15 cm do dossel. O ganho de peso m?dio di?rio dos animais suplementados com feno de leguminosas foi semelhante ao ganho obtido pelos animais suplementados com farelo de soja nos quatro ciclos de pastejo. O ganho de peso vivo total foi maior do que os animais suplementados apenas com mistura m?ltipla nos dois primeiros ciclos de pastejo. Os fenos de Leucena e de Gliric?dia podem ser indicados para suplementa??o de ovinos mantidos em pasto

Leucaena leucocephala and Sesbania sesban in dry form were fed as supplements to goats feeding on a low quality basal diet of barley straw. Each browse supplement was fed at four levels: 0 %, 0.83 % liveweight (LW), 1.66 % LW and at ad libitum. The intakes of dry matter (DM) and organic matter (OM), DM and OM digestibility, nitrogen (N) digestibility and balance, and liveweight gain were evaluated during a 5 week trial. For goats offered both leucaena and sesbania there was no significant (p<0.05) difference in DM or OM intakes between 0.83 % LW and 1.66 % LW levels of browse supplementation. When both lecaena and sesbania were offered ad libitum the DM and OM intakes were significantly (p<0.05) lower than for either 0.83 % LW or 1.66 % LW level of supplementation. Feeding both leucaena and sesbania increased the DM and OM digestibility coefficients significantly over thos of the controls. The growth rates for goats supplemented with leucaena at various levels were not significantly different from each other. For the goats offered sesbania at ad libitum, their growth rates were significantly lower than for those fed sesbania at either 0.83 % LW or 1.66 % LW. The apparent digestibility of nitrogen (ADN) was not significantly different among leucaena supplemented treatments. For goats offered sesbania, the ADN was significantly higher than for the controls. The ability of browse supplements to increase intakes and digestibility of both dry matter and organic matter is discussed.

The major antinutritive factor in Leucaena for ruminants is condensed tannin (CT). CT bind proteins, incurring a negative effect on protein utilisation. The two major factors affecting the ability of CT to bind protein have been purported to be CT size and the pH of the reaction environment. To test these hypotheses the protein precipitating capacities of CT extracted from four promising Leucaena genotypes, L. leucocephala (K636), L. pallida (CQ3439), L. trichandra (CPI46568), and L. collinsii (OFI52/88) were assessed. L. leucocephala had approximately half the ability to precipitate protein on a g/g basis than L. pallida or L. trichandra while L. collinsii gave no measurable ability to precipitate protein (reaction environment=pH 5.0). Increasing or decreasing the pH of the reaction solution away from pH 5.0 (the isoelectric point of the protein) reduced the ability of CT from all the species to precipitate protein; the decrease being higher a pH 2.5 than at pH 7.5. At pH 2.5 L. leucocephala CT completely lost its capacity to precipitate protein. The relatively poor ability of L. leucocephala CT to bind protein at pH’s approximating those at the abomasum suggests L. leucocephala may have the greatest potential of the four Leucaena’s tested for increasing the extent of feed protein escaping ruminant degradation for later release and digestion in the small intestine, hence increasing the total amount of protein absorbed by ruminants. CT fractions from each Leucaena were also separated into individual CT’s, by size-exclusion chromatography and examined for protein precipitating capacity. In general it was found that the larger sized CT of the accessions L. pallida and L. trichandra could precipitate more protein than the smaller sized CT. This pattern was not found for L. leucocephala.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 5 uppsatser.

Submitted by (ana.araujo@ufrpe.br) on 2016-05-18T16:23:27Z No. of bitstreams: 1 Adalberto Gomes de Araujo.pdf: 1912427 bytes, checksum: f5afb060ed8c40727f32cece528acc33 (MD5) / Made available in DSpace on 2016-05-18T16:23:27Z (GMT). No. of bitstreams: 1 Adalberto Gomes de Araujo.pdf: 1912427 bytes, checksum: f5afb060ed8c40727f32cece528acc33 (MD5) Previous issue date: 2005-06-15 / The objective of this work was to use multivariate and univariate statistical methods, in the selection of independent variables, in mathematical models, in the construction of volume tables for Leucaena leucocephala, looking for reduction in time and costs, without loss of precision. The data came from an experiment carried out at the Experimental Station of the Institute of Agriculture Research (IPA), Caruaru-PE. It was used 201 trees of leucena that had their volumes (dependent variable) measured by the method of Smalian, and 20 variables independent measured in the same trees. For the selection of the independent variables the following methods were used: Principal Components, Cluster Analysis, Maximum and Minimum R2, Stepwise, Forward, Backward and Criterion of Akaike. In the general, the univariate and multivariate methods used in the selection of independent variables for volume models, showed similar responses, even though they had different structures in relation to the independent variables, since the number of those variables is high. Besides the applied statistical tests, the researcher'sjudgment about the relevance of the selected independent variables in the final equations has a great importance, mainly, in the reduction of costs and sampling errors. / O objetivo deste trabalho foi utilizar métodos estatísticos univariados e multivariados na seleção de variáveis independentes, em modelos matemáticos, para a construção de tabelas de volumes para Leucaena leucocephala, visando reduzir tempo e custos sem perda de precisão. Os dados foram provenientes de um experimento conduzido na Estação Experimental da Empresa Pernambucana de Pesquisa Agropecuária (IPA), Caruaru-PE. Foram utilizadas 201 árvores de leucena, que tiveram seus volumes cubados pelo método de Smalian, e 20 variáveis independentes medidas nas mesmas árvores. Para a seleção das variáveis independentes foram utilizados os seguintes métodos: Componentes Principais, Análise de Agrupamento, R2 Máximo e Mínimo, Stepwise, Forward, Backward e Critério de Akaike. No geral, os métodos univariados e multivariados empregados no descarte de variáveis independentes para modelos volumétricos, conduzem a respostas semelhantes, mesmo que possuam estruturas diferentes em relação às variáveis independentes, desde que o número dessas variáveis seja elevado. Além dos testes estatísticos aplicados, o julgamento do pesquisador sobre a relevância das variáveis selecionadas nas equações resultantes, é de grande importância, principalmente, na redução de custos e do erro de amostragem

Submitted by (ana.araujo@ufrpe.br) on 2016-07-05T20:19:01Z No. of bitstreams: 1 Franklin Tupinamba Paes de Andrade Viera.pdf: 337732 bytes, checksum: 0600dc25608a782e0a42c10d6cdd44f2 (MD5) / Made available in DSpace on 2016-07-05T20:19:01Z (GMT). No. of bitstreams: 1 Franklin Tupinamba Paes de Andrade Viera.pdf: 337732 bytes, checksum: 0600dc25608a782e0a42c10d6cdd44f2 (MD5) Previous issue date: 2006-02-22 / The main objective of the present work was to evaluate the use of the leucena [Leucaena leucocephala (Lam.) of Wit.] as direct pasture in the field. A multivariate silvopastoral experiment with repeated measures, carried out in the experimental station of Pernambucana Company of Agricultural Research (IPA) in Caruaru, Agreste of Pernambuco, was used for this purpose. The plant spacing of 0,5mX1,0m, 1,0mX1,0m and 1,5mX1,0m with the height of cut of 20cm, 40cm and 60cm, was tested. The measurements have been carried through at same month of the year (August) along five years. The presented result shows that the measures along the time are correlated and there were significant differences among the plant spacing during the period of the experiment. No significant differences among the heights of cuts and its interactions with the plant spacing occurred. Because of a larger number of plants per unit area, yielding greater productivity of biomass per hectare, the plant spacing of 0,5mX1,0m is recommended for silvopastoral systems in the Agreste of Pernambuco. / O principal objetivo do presente trabalho foi avaliar o uso da leucena [Leucaena leucocephala (Lam.) de Wit.] como pastagem direta no campo, utilizandose para tanto de um experimento silvipastoril multivariado, com medidas repetidas, realizado na região Agreste do Estado de Pernambuco. Estudou-se a leucena submetida a diferentes espaçamentos e alturas de corte com a finalidade de produção de biomassa. O experimento foi realizado na estação experimental da Empresa Pernambucana de Pesquisa Agropecuária (IPA), no município de Caruaru. Testaram-se os espaçamentos 0,5mX1,0m ; 1,0mX1,0m e 1,5mX1,0m e as alturas de corte 20cm, 40cm e 60cm. As medições foram realizadas numa mesma época do ano (mês de agosto) em cinco anos. Os resultados apresentados mostraram que as medidas ao longo do tempo são correlacionadas e que houve diferenças significativas entre os espaçamentos durante todo o período do experimento. Não ocorreram diferenças significativas entre as alturas de cortes e suas interações com os espaçamentos em todos os tempos. Por se usar um maior número de plantas por unidades de área e conseqüentemente, maior produtividade de biomassa por hectare, recomenda-se o uso de espaçamento 0,5mX1,0m em sistemas silvipastoris com leucena no Agreste de Pernambuco.

En Amazonie orientale, l’agriculture familiale contribue significativement à la transformation des écosystèmes forestiers en pâturages. La mise en valeur pastorale se fait généralement de manière monospécifique avec une Poacée pérenne d’origine africaine (Brachiaria brizantha cv. Marandu) qui constitue la principale offre fourragère. Mais les pratiques pastorales mises en oeuvre sur une exploitation conduisent souvent à une dégradation des pâturages, qui se manifeste par une prolifération des plantes adventices. Le pâturage a été modifié par l’introduction de deux Fabacées pérennes fourragères originaires d’Amérique Latine, l’une herbacée (Arachis pintoï cv. Amarelo) et l’autre ligneuse (Leucaena leucocephala). Pendant la saison sèche, nous avons étudié les interactions entre B. brizantha et des Fabacées fourragères implantées. Cette étude est la première approche intégrée (écophysiologie) qui étudie les caractéristiques adaptatives et les effets des Fabacées sur la capacité de résistance à la contrainte hydrique des pâturages à partir des évolutions des échanges gazeux foliaires, du potentiel hydrique et de l’état hydrique du sol. Le dispositif expérimental était composé de cinq parcelles de 100 m2 isolées du bétail correspondant à cinq traitements différents. Les trois espèces étudiées ont été cultivées seules et en association. Trois répétitions ont été réalisées pour chaque traitement afin de valider statistiquement les résultats et prendre en compte la variabilité spatiale du sol. En monoculture, les valeurs de conductances stomatiques de B. brizantha sont relativement élevées au regard des conditions climatiques par rapport à des valeurs habituelles de plantes C4 au champ alors que les valeurs d’assimilations nettes sont celles mesurées couramment. A. pintoï et L. leucocephala possèdent des valeurs de conductances stomatiques et d’assimilations mesurées habituellement sur les plantes C3 au champ. En situation de sécheresse, les trois espèces étudiées en monoculture adoptent un mouvement de fermeture stomatique 30 jours après l’arrêt des pluies et ajustent ainsi leur conductance sur l’épuisement de la réserve utile du sol. Cette stratégie permet le maintien de l’activité photosynthétique indispensable à la survie cellulaire et de maintenir une transpiration suffisante pour réguler leur température. Les trois espèces survivent par évitement de la sécheresse, en réduisant leur surface foliaire active et en fermant leurs stomates dès l’abaissement du potentiel hydrique. B. brizantha a le même comportement lorsqu’il est cultivé seul ou associé à A. pintoï que ce soit au niveau de la conductance stomatique, de l’assimilation de CO2 ou de l’efficience instantanée de l’eau. Cependant, son potentiel hydrique est affecté plus précocement au cours d’un stress hydrique lorsqu’il est en concurrence avec A. pintoï. Dans le cas de cette association, notre étude montre que la présence de B. brizantha a un effet négatif sur les activités photosynthétiques et donc sur la production de biomasse d’A. pintoï, espèce considérée pourtant comme sciaphile. Enfin, les fonctions métaboliques de B. brizantha sont réduites lorsqu’il est associé à L. leucocephala du fait de l’ombrage. L. leucocephala évite la sécheresse en réduisant sa surface foliaire. L’augmentation d’insolation en fin de saison sèche affaiblit cependant les plantes associées aux strates inférieures et réduit la quantité de fourrage disponible sur pied. Nous proposons aux agriculteurs de mettre en place une gestion durable de leurs pâturages par la création d’associations végétales fourragères adaptées aux contraintes biotiques et abiotiques. / In the Eastern Amazon region (Pará, Brazil), smallholder farming significantly contributes to the transformation of the Amazonian rain forest ecosystem into pasture land that typically includes a single species, generally a perennial fodder grass (Poaceae) originating from Africa (Brachiaria brizantha cv. Marandu). Such pastures rapidly lose their sustainability and get invaded by weeds. To prevent these effects, two imported perennial fodder species of the Fabaceae family (Arachis pintoï cv. Amarelo and Leucaena leucocephala Lam.) have been mixed with the African grass Brachiaria and the interrelations between B. brizantha and the Fabaceae species have been studied. In this unique ecophysiological study, plant parameters, such as gas exchange and plant water potential have been correlated with soil parameters, such as soil water content. The final goal was to assess the impact of the Fabaceae plants on pasture tolerance to water deficit. The experimental setting included five treatments applied to 100 m2 fenced plots to keep cattle away. Treatments corresponded to various combinations between the grass and the two Fabaceae species. Three biological repeats were set up for each treatment for statistical significance and in order to account for soil structure variability. In monospecific plots, B. brizantha exhibited stomatal conductance values higher than those expected from typical C4 species whereas net CO2 assimilation rates were normal. A. pintoï and L. leucocephala had usual stomatal conductance values for field-cultivated C3 plants. In response to drought, a general adjustment in stomatal conductance was observed 30 days into the dry season (i.e. without rain), suggesting that the plants limited transpiration rates according to the progressive decrease in soil water content. This strategy allowed them to maintain photosynthetic activities and to supply photosynthates to their tissues while limiting rises in temperatures. Upon exhaustion of soil water cotent, decreases in leaf water potentials were observed and plants escaped drought by reducing their leaf area and by abruptly closing their stomata. Brachiaria’s responses to drought were similar in mixed and monospecific plots regarding stomatal conductance, net CO2 assimilation rate or real-time water efficiency. However, when grown in mixed plots with A. pintoï, Brachiaria’s leaf water potential decreased rapidly after the onset of drought, due to the competition for water. In a A. pintoï ! Brachiaria plot, Brachiaria had a negative impact on A. pintoï photosynthetic activities and biomass production, even though the latter was considered as a shade plant species. On the other hand, Brachiaria metabolic activities were reduced in L. leucocephala ! Brachiaria combinations, due to the interception of light supply by L. leucocephala. L. leucocephala avoided water deficit by reducing leaf area. The resulting increase in light intensity reaching the lower strata, toward the end of the dry season weakened the shortest plants and limited fodder production. In conclusion, we propose that farmers implement pasture sustainability by developing crop mixing, using fodder species adapted to abiotic stresses. Furthermore, our results show that several crop combinations represent viable solutions to the perpetuation of new pastures. Each fodder species presents specific drought adaptation features. Combining them could be beneficial if pastoral pressure was allowed to develop according to the plants tolerance level. Improvements in fodder production and diversity could extend the life-span of smallholder settlements and as a result slow down deforestation

Este experimento teve por objetivo avaliar a influência da adição de Leucaena leucocephala como fonte protéica em dietas de ovinos no consumo voluntário, na digestibilidade total dos nutrientes e na retenção de nitrogênio. Para realização deste estudo foram utilizadas 6 dietas à base de feno de tifton e 12 ovinos machos, castrados da raça Santa Inês (35 kg) em changeover incompleto com três períodos de 21 dias cada. As dietas L20, L40 e L60 continham leucena em três níveis de inclusão (20, 40 e 60%), respectivamente, e as demais dietas, CL20, CL40 e CL60, continham concentrado como fonte protéica e foram denominadas de dietas controles. As causas de variação dos resultados foram analisados através da análise de variância e as médias (LSM, least square means) foram comparadas por contrastes não ortogonais e por regressão linear e quadrática utilizando os procedimento GLM do software SAS, 2000. O consumo voluntário de MS (CVMS) variou entre 52,0 (L20) e 67,7 (L40) g kgPV-0,75 e não houve efeito significativo (P>0,05) da utilização de leucena como fonte protéica. Os níveis de leucena influenciaram o CVMS apresentando diferenças significativas entre as dietas L20 e L40 (P<0,05). Os animais alimentados com a dieta L40 apresentaram aumento de 30% no consumo de MS (67,7 g kgPV-0,75) em relação a dieta L20 (52,0 g kgPV-0,75). Os resultados observados no ensaio de digestibilidade indicaram diminuição (P<0,05) da digestibilidade aparente da MS com a adição de leucena com valores de 39,0; 37,4; 39,0 % para as dietas L20, L40, L60 e 51,1; 50,4; 52,8 % para CL20, CL40 e CL60, respectivamente. A digestibilidade aparente da PB também foi reduzida com a adição de leucena (P<0,05) em comparação às dietas controles, com valores de 33,7; 32,0; 36,7; 52,2, 63,0 e 66,7 para as dietas L20, L40, L60, CL20, CL40 e CL60, respectivamente. A digestibilidade aparente das fibras foi afetada com a inclusão de leucena (P<0,05). Os coeficientes de digestibilidade de FDN foram 39,2; 35,7; 34,9; 50,0; 45,9; 45,3 e de FDA foram 34,8; 26,9; 25,1; 47,0; 55,7; 54,1 para as dietas L20, L40, L60, CL20, CL40 e CL60, respectivamente. A adição de leucena ou os níveis propostos de sua inclusão não alteraram a retenção de N entre as dietas com e sem leucena (P>0,05) apresentando valores de 1,4; 0,9; 3,3; 0,4; 3,8; 5,4 (L20, L40, L60, CL20, CL40 e CL60, respectivamente). As três dietas com leucena propiciaram maiores perdas de N nas fezes (6,2; 11,4; 12,4 g d-1, respectivamente; P<0,01) e menores teores de N na urina (4,0; 4,4; 6,3, respectivamente; P<0,01) que as dietas controles. A perda de N nas fezes ou na urina aumentou linearmente com o aumento do nível de leucena na dieta (P<0,01). Estes resultados mostraram que a utilização de leucena em dietas de ovinos Santa Inês, não afetou o CVMS e a retenção de N em comparação com dietas tendo concentrado como fonte protéica. Entretanto, reduziu a digestibilidade dos nutrientes, as perdas de N na urina e aumentou as perdas de N nas fezes. Entre as dietas com leucena, o nível de 40% de inclusão propiciou um CVMS máximo e as perdas de N nas fezes e na urina apresentaram um comportamento linear. / This study intended to investigate the Leucaena leucocephala (leucaena) addition as a protein supplement in sheep diet upon the voluntary dry matter intake, nutrient digestibility and nitrogen (N) retention. The experiment was conducted in a change-over design using 6 diets and 12 male Santa Inês sheep in 3 periods of 21 days. The diets L20, L40 and L60 consisted of Cynodon x cynodon (tifton) hay and leucaena at 3 levels, (20, 40 and 60%) of the total dry matter (DM), respectively. The control diets, CL20, CL40 and CL60, consisted of tifton hay and concentrate, at the same rate of protein as L20, L40 and L60, respectively. Sources of variation were analyzed by Analyses of Variance and the least square means were compared by non-orthogonal contrasts and linear and quadratic regression according to GLM procedures from SAS (2000). Dry matter intake (DMI) ranged from 52,0 (L20) to 67,7 (L40) g kgBW- 0 , 7 5d- 1. There was no significant effect with addition of leucaena (P>0,05). Significant differences on DMI were observed among the three levels of leucaena (P<0,05). Animals fed L40 showed 30% increase of DMI (67,7 g kgBW-0,75) related to L20 (52,0 g kgBW-0,75). Results from digestibility trial showed lower apparent digestibility of DM (P<0,05) with values of 39,0; 37,4; 39,0; 51,1; 50,4; 52,8 % for diets L20, L40, L60, CL20, CL40 and CL60, respectively. Apparent digestibility of PB was also reduced with addition of leucaena (P<0,05) related to control diets, showing values of 33,7, 32,0 36,7 % for L20, L40, L60 and 52,2, 63,0, 66,7 % for CL20, CL40 and CL60, respectively. Apparent digestibility of fiber was affected with inclusion of leucaena (P<0,05). The coefficients of NDF digestibility were 39,2; 35,7; 34,9; 50,0; 45,9; 45,3 and ADF were 34,8; 26,9; 25,1; 47,0; 55,7; 54,1 for diets L20, L40, L60, CL20, CL40 and CL60, respectively. Either addition or level of leucaena did not affect N retention (P>0,05) and presented values of 1,4; 0,9; 3,3; 0,4; 3,8; 5,4 for L20, L40, L60, CL20, CL40 and CL60, respectively. Diets containing leucaena led to an increase of faecal N losses (6,2; 11,4; 12,4 g d-1, respectively; P<0,01) and reduction of urinary N losses (4,0; 4,4; 6,3, respectively; P<0,01). Faecal and urinary N increased linearly (P<0,01) with level of supplementation. These results show that the use of leucaena for Santa Inês sheep did not affect DMI and N retention comparing to control diets; however, it reduced nutrients digestibility, urinary N and increased faecal N. Among level of leucaena included, the level of 40% caused maximum DMI and faecal and urinary N losses presented a linear behaviour.

O presente trabalho teve como objetivo avaliar os efeitos do uso de leucena (Leucaena leucocephala (Lam.) de wit), em dietas para bovinos com ou sem adição de levedura (Saccharomyces cerevisiae) sobre a digestão (degradabilidade e digestiilidade), fermentação (produção de ácido graxos voláteis, amônia e metano) e população de protozoários no rúmen. Foram utilizados quatro bovinos machos mestiços, com peso vivo médio de 797 kg, canulados no rúmen em experimento com delineamento Quadrado Latino 4x4 em arranjo fatorial 2x2 com dois níveis leucena (20% e 50%) com feno de Cynodon dactylon cultivar coast-cross na presença ou ausência da levedura. Os tratamentos foram denominados: 20S = 20% de feno de leucena + 80% de de coast-cross ; 50S = 50% de feno de leucena + 50% de de coast-cross; 20L = 20% de feno de leucena + 80% de de coast-cross + 10 g de levedura; 50L = 50% de feno de leucena + 50% de de coast-cross + 10g de levedura. Os parâmetros ruminais avaliados foram: produções de ácidos graxos voláteis (AGVs); concentração de amônia; pH; produção de gás metano; taxa de passagem do líquido; degradabilidade in situ da MS, FDN e PB dos fenos de leucena e coast-cross; digestibilidade in vitro da MS dos fenos de leucena e coast-cross; contagem diferencial dos gêneros de protozoários ciliados. Houve efeitos da interação entre níveis de leucena e levedura nas dietas sobre as concentrações médias dos AGVs totais (P<0,05). As concentrações de ácido acético não apresentaram diferenças entre tratamentos. Mas as concentrações de ácido propiônico mostraram efeitos significativos para níveis de leucena na dieta e da interação N x L (P<0,05), com os maiores valores médios obtidos para o ácido propiônico em nível mais alto de leucena com levedura (19,14 mM). O aumento do nível de leucena favoreceu uma maior produção de ácido propiônico e esse efeito foi potencializado pela adição de levedura. Não houve diferenças na produção de ácido butírico nos níveis de leucena e de levedura (P>0,05) mas foram observados efeitos significativos da interação, evidenciando maiores concentrações do ácido butiríco no tratamento 20L. Não foram observadas diferenças (P>0,05), nas concentrações de amônia no rúmen, variando de 18,71 a 21,28 mg/100 mL no líquido ruminal. Houve diferença (P<0,05) na emissão de gás metano pelos animais, recebendo os diferentes tratamentos, ocorreu uma redução na produção de metano na dieta com nível elevado de leucena contendo levedura. Os valores encontrados para a cinética ruminal não foram afetados pelos tratamentos (P>0,05). A população de protozoários ciliados no rúmen sofreu alterações conforme o tratamento aplicado, tanto na concentração como na composição final da fauna, indicando um efeito associativo que ocorreu com o aumento de leucena na dieta juntamente com a levedura ou mecanismo de ação semelhante de ambos, dependendo do nível de leucena na dieta. / The present work had as objective to evaluate the effect of the use of leucaena (Leucaena leucocephala (Lam.) of Wit) in diets for bovines with or without yeast addition (Saccharomyces cerevisiae) on the digestion (degradability and digestibility), fermentation (production of volatile fatty acids, ammonia and methane) and ciliate protozoa population in rumen. Four crossbred male cattle, with average body weight of 797 kg, with rumen cannula were utilized in a Latin Square assay design 4x4, in factorial arrangement (2 x 2) with two levels of leucaena (20% and 50% DM) with hay of Cynodon dactylon cv coast-cross with or without addition of yeast. The treatments had been called: 20S = 20% of leucena hay + 80% of hay of coast-cross; 50S = 50% of leucena hay + 50% of hay of coast-cross; 20L = 20% of leucena hay + 80% of hay of coast-cross + 10 g of yeast and 50L = 50% of leucena hay + 50% of hay of coast-cross + 10g yeast. The ruminal parameters evaluated were: volatile fatty acids production; ammonia concentration; pH; gas production of methane; fluid outflow; in situ degradability in situ of the DM, NDF and CP of leucena and coast-cross hays; DM in vitro digestibility of leucena and coast-cross hays and concentration and generic counting of the ciliate protozoa. It was observed effect of the interaction between leucena levels and yeast in the diets on average total concentrations of VFA. No differences were observed in the concentrations of acetic acid among the treatments. But the propionic acid concentrations had shown significant effect for levels of leucena in the diet and interaction, with higher values obtained in the high leucaena level with yeast addition (19.14 mM). The increase of the leucaena level favored a higher production of propionic acid and this effect was powed by the yeast addition. There were no differences in the butyric acid production among the treatments, but significant effect of the interaction had been observed, evidencing higher concentrations of butyric acid in the treatment 20L. No difference had been observed in the rumen ammonia concentrations, varying from 18.71 to 21,28 mg/100 mL of ruminal liquid. A reduction in the methane production was observed in the animals receiving higher level of leucena with yeast addition. The values found for the kinetic ruminal had not been affected by the treatments. There was observed alteration in the rumen protozoa population according to treatment, as much in the concentration as mainly in the final composition of the fauna, indicating to have an associative effect that occurs with the increase of leucena in the diet together with the yeast addition or occurs a mechanism of similar action of both depending on the level of leucena in the diet.