Conselho Nacional de Desenvolvimento Científico e Tecnológico / The aim of the present study was to evaluate the effect of the use of Alexander grass silage (Urochloa plantaginea) on body tissues that are not part of the carcass, as well as the quantitative and qualitative aspects of the carcass and meat from feedlot finished steers. It was used 12 castrated, pure and crossbred Charolais x Nellore steers, age and initial weight were 20 months and 245 kg respectively, distributed in two different treatments: Alexander grass silage (AS) = animals fed with 51% of Alexander silage and 49% of concentrate and, sorghum silage (SS) = animals fed with 53% sorghum silage and 47% of concentrate (control group). The diet was calculated searching to meet the minimal nutritional requirements in order to obtain an average daily weight gain of 1.2 kg/animal and, estimating a dry matter intake of 2.5 kg/100 kg alive. The experimental design used was randomized blocks with two treatments and six samples per treatment; each experimental unit consisted of one animal. The slaughter weight (SW), empty body weight (EBW) and, the relationship between EBW/SW were similar for animals in the tested roughage, with mean values of 442.66 kg, 381.45 kg and 0.86 respectively. The rumen-reticulum expressed in kg and, the gastrointestinal content in absolute or relative weight for 100 kg of empty body weight (%EBW) were higher for AS animals while, the liver in %EBW was higher for SS animals. AS animals showed higher kidney fat deposition, both in absolute weight and %EBW and, increased deposition of fat in the abomasum %EBW. However, in total numbers, the fats that are not part of the carcass did not differ between treatments. Hot carcass yield and fat thickness were similar between animals in the tested roughage, with an average of 58.8% and 4.7 mm, respectively. The same behavior was observed for meat color, texture and marbling. Nevertheless, the meat from AS animals showed a greater muscle and fat liquid loss when subjected to cooking. There was no difference in meat chemical composition between the tested roughage with mean values of 20.27, 76.17, 2.11 and 1.14% for crude protein, moisture, ether extract and mineral matter respectively. / O objetivo do presente estudo foi avaliar o efeito do uso da silagem de papuã (Urochloa plantaginea) sobre os tecidos corporais que não perfazem a carcaça, bem como, os aspectos quantitativos e qualitativos da carcaça e da carne de novilhos terminados em confinamento. Utilizaram-se 12 bovinos machos castrados, puros e mestiços Charolês x Nelore, com idade e peso médio inicial de 20 meses e 245 kg respectivamente, distribuídos em dois tratamentos: Silagem de Papuã (SP) = animais recebendo 51% de silagem de papuã e 49% de concentrado e Silagem de Sorgo (SS) = animais recebendo 53% de silagem de sorgo e 47% de concentrado (grupo controle). A dieta foi calculada buscando-se atender os requerimentos mínimos nutricionais, a fim de obter-se um ganho de peso médio diário de 1,2 kg/animal, estimando-se um consumo de matéria seca 2,5 kg/100 kg de peso vivo. O delineamento experimental utilizado foi de blocos ao acaso, com dois tratamentos e seis amostras por tratamento, sendo cada unidade experimental composta por um animal. O peso de abate (PAB), peso de corpo vazio (PCV), assim como a relação entre PCV/PAB foram similares entre os animais dos volumosos testados, apresentando valores médios de 442,66 kg, 381,45 kg e 0,86 respectivamente. Os órgãos rúmen-retículo expressos em kg, e o conteúdo gastrintestinal tanto em peso absoluto ou relativo a 100 kg de peso de corpo vazio (%PCV), foram superiores nos animais SP, já o órgão fígado em %PCV foi superior nos animais SS. Os animais SP apresentaram maior deposição de gordura renal, tanto em peso absoluto quanto em %PCV, e maior deposição de gordura do abomaso em %PCV. Porém na totalidade, as gorduras que não perfazem a carcaça não apresentaram diferença entre os tratamentos. O rendimento de carcaça quente e a espessura de gordura foram similares entre os animais dos volumosos testados, apresentando médias de 58,8% e 4,7 mm, respectivamente. Mesmo comportamento se observou quanto à coloração, textura e marmorização da carne. No entanto, a carne provenientes de animais SP apresentou maior perda de líquidos e gordura muscular quando submetidas à cocção. Não houve diferença na composição química da carne entre os volumosos testados, apresentando valores médios de 20,27; 76,17; 2,11 e 1,14% para proteína bruta, umidade, extrato etéreo e matéria mineral respectivamente.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The work was carried out to evaluate the defoliation patterns and quantify the leaf tissue flows in Alexandergrass, grazed by beef heifers in different feeding systems, in rotational grazing method. The experimental design was completely randomized with repeated measures, three levels of supplementation with whole rice bran (0; 0.5 and 1% of body weight) and two area replications. The supply of whole rice bran for heifers grazing in Alexandergrass allows can increase 13% the stocking rate. The leaf tissue flows, consumption of leaf blades and the grazing intensity are not changed by supplement. Regardless of the system feeding the heifers graze the leaf blades growing in a smaller period of time compared to other types of leaf, which allows the leaf crop top extract canopy. / Objetivou-se avaliar os padrões de desfolhação e quantificar os fluxos de tecidos foliares em papuã, pastejado por novilhas de corte, em diferentes sistemas alimentares, em método rotativo de pastejo. O delineamento experimental foi o inteiramente casualizado, com medidas repetidas no tempo, três níveis de suplementação com farelo de arroz integral (0; 0,5 e 1 % do peso corporal) e duas repetições de área. O fornecimento de farelo de arroz integral para novilhas em pastejo em papuã permite aumentar 13% a taxa de lotação. Os fluxos de tecidos foliares, o consumo de lâminas foliares e a intensidade de pastejo não são alterados pelo fornecimento de suplemento. Independente do sistema alimentar as novilhas pastejaram as lâminas foliares em expansão num menor intervalo de tempo em relação aos demais tipos de folha, o que permite a colheita de folhas do extrato superior do dossel.

En dépit de ses succès, le modèle agricole fondé sur un recours massif aux intrants est mis à mal du fait de ses externalités négatives. L’agroécologie propose de substituer aux intrants le pilotage des processus écologiques naturels. La production cidricole est engagée dans cette démarche. Nous avons cherché à évaluer l’apport de deux types d’aménagements agro-écologiques : les haies et les mélanges fleuris. Nous avons caractérisé la faune entomologique présente dans 14 vergers cidricoles du nord-ouest de la France (Bretagne, Normandie) et son évolution au cours de la saison. L’analyse des données collectées a confirmé que les aménagements étaient attractifs pour les ennemis naturels des ravageurs des pommiers.L’étude des dynamiques d’abondance du puceron cendré (Dysaphis plantaginea) au cours de la saison permet de hiérarchiser les contributions des différents ennemis naturels à la régulation de ses populations et de montrer leur complémentarité temporelle. Les syrphes et les coccinelles jouent le rôle principal avec une action plus précoce des premiers. Le rôle favorable au puceron de la présence des fourmis est confirmé. Les mélanges fleuris réduisent les abondances du puceron et accroissent celles de la plupart des groupes d’ennemis naturels. Au contraire, la présence des haies est favorable au ravageur. Un dispositif d’exclusion des fourmis réduit significativement leurs abondances et celles des pucerons et augmente les abondances des syrphes et des coccinelles, confirmant l’effet délétère des fourmis sur les ennemis naturels. Enfin, le prototype d’un indicateur du / In spite of their successes, agricultural systems based on the massive use of inputs are questioned for their negative externalities. Agroecology offers to substitute inputs with natural ecological processes. Apple-cider production is engaged in the development of agroecology. Here, we aimed at assessing the benefits provided by two types of agroecological infrastructures: hedgerows and flower strips. We characterised the entomological fauna encountered in 14 cider-apple orchards in northwestern France (Bretagne, Normandy) and its evolution along the season. Data analysis confirmed agroecological infrastructure attractiveness to apple pest natural enemies. The observation of rosy apple aphid (Dysaphis plantaginea) population dynamics allows hierarchizing the contributions of several natural enemies to pest control and demonstrates their temporal complementaritySyrphids and coccinellids are the most effective with the firsts being the most precocious. The beneficial role to aphids of ant presence is confirmed. Flower strips reduce aphid abundances and increase the abundances of most natural enemy groups. Conversely, hedgerows are favourable to the pest. An ant-excluding device reduces significantly ant and aphid abundances and increases syrphid and coccinellid abundances, confirming the deleterious effect of ants on natural enemies. Finally, a prototype of an indicator of biological control potential against D. plantaginea was designed.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The leaf biomass flows of Alexandergrass (Urochloa plantaginea (Link) Hitch), the intensity and frequency of defoliation were evaluated using Zero, 100, 200 or 300 kg ha-1 of nitrogen (N), in the form of urea. The grazing method was continuous with variable number of animals to keep the forage mass in 3000 kg ha-1 DM. The experimental animals were Angus heifers with age and initial average body weight of 15 months and 241.5±5.7 kg, respectively. The experimental design was completely randomized following a repeated measure arrangement measures with four treatments and variable number of experimental units. Application of 100 kg ha-1 N provided higher leaf blades growth flow. The senescence and intake fluxes and defoliation intensity were similar in N fertilizer rates used. The return frequency (days) was influenced by N rates and evaluation periods. It is recommended using 100 kg ha-1 N in Alexandergrass pasture. / Os fluxos de biomassa foliar do papuã (Urochloa plantaginea (Link) Hitch), a intensidade e frequência de desfolha foram avaliados com o uso de Zero, 100, 200 ou 300 kg ha-1 de nitrogênio (N), na forma de ureia. O método de pastejo foi contínuo com número variável de animais para manter a massa de forragem em 3000 kg ha-1 de MS. Os animais experimentais foram bezerras Angus com idade e peso corporal médio inicial de 15 meses e 241,5±5,7 kg, respectivamente. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo, com quatro tratamentos e número variável de unidades experimentais. O uso de 100 kg ha-1 de N proporcionou maior fluxo de crescimento de lâminas foliares. Os fluxos de senescência e de consumo e a intensidade de desfolha foram similares nas doses de N utilizadas. A frequência de retorno (dias) foi influenciada pelas doses de N e períodos de avaliação. É recomendada a utilização de 100 kg ha-1 de N em pastagem de papuã.

Dans le contexte politique (réduction 50% de l’utilisation des pesticides à échéance de 2018 -Plan Ecophyto) et social actuel (mise en place de modes de production plus respectueux pour l'environnement), la sévérité des dommages causés par le puceron cendré du pommier, Dysaphis plantaginea Passerini (Hemiptera : Aphididae), surtout en agriculture biologique, rend nécessaire la mise au point de solutions alternatives s’appuyant sur le rôle des ennemis naturels. Nous avons donc essayé d’apporter des éléments nouveaux sur la connaissance des relations entre le puceron cendré et ses ennemis naturels et sur les conditions à même de favoriser leur action. Des suivis hebdomadaires des arthropodes présents sur les rameaux infestés par D. plantaginea, ont mis en évidence l’effet négatif des auxiliaires sur les populations de D. plantaginea, sans pour autant atteindre une véritable régulation à même d’éviter les dégâts économiques. Nous avons également montré l’action favorisante des fourmis sur la dynamique du puceron cendré et négative sur celle des auxiliaires. Nous avons pu identifier trois groupes d’auxiliaires dominants avec une arrivée séquentielle marquée : les syrphes, dont l’installation coïncide avec le début de l’infestation de D. plantaginea, puis les coccinelles et les forficules qui arrivent plus tardivement. Pour que les auxiliaires jouent un rôle plus important contre D. plantaginea, il faut d’autres pratiques permettant d’abaisser significativement le nombre de traitements pesticides. Une innovation très récente permet la réduction drastique des traitements insecticides : les filets Alt’Carpo. Malgré son influence négative sur l’abondance et la richesse du cortège des auxiliaires présents dans les colonies de D. plantaginea, surtout les coccinelles, cette technique freine le développement des populations de D. plantaginea à l’échelle du rameau ou de l’arbre lorsque les filets sont fermés après la floraison (en conformité avec les préconisations contre le carpocapse). Cependant, la réduction des populations de D. plantaginea sous les filets requiert la présence d’au moins un stade actif d’auxiliaire par rameau, ce qui interroge sur la réalité de la régulation de ce ravageur par le simple usage des filets. Sur la base de leur précocité, pour Episyrphus balteatus De Geer (Diptera : Syrphidae) et de leur abondance dans les colonies de D. plantaginea, pour Forficula auricularia Linnaeus (Dermaptera : Forficulidae) et E. balteatus, ces deux espèces apparaissent comme de bons candidats pour la régulation de D. plantaginea. Nos études en conditions contrôlées ont démontré leur potentiel régulateur sur D. plantaginea, en particulier aux stades les plus âgés. L’efficacité optimale intervient à 20°C pour les deux prédateurs, pour lesquels nous n’observons par ailleurs pas d’interaction négative lorsqu’ils sont associés en présence de fortes densités de D. plantaginea. Sur la base de ces résultats de laboratoire nous avons analysé les possibilités de lâchers printaniers de ces deux prédateurs sur de jeunes colonies de D. plantaginea. Dans nos conditions expérimentales en vergers de pommiers, des lâchers précoces de larves du 3ème stade de F. auricularia n’ont pas permis de limiter les populations de D. plantaginea, confirmant la difficulté des lâchers de prédateurs en cultures de plein champ. De la même manière, des lâchers précoces d’E. balteatus pourtant réalisés sous filets Alt’Carpo restent sans effet sur l’infestation par D. plantaginea. Cette thèse, en s’appuyant sur des essais en conditions contrôlées, semi contrôlées et de plein champ, constitue une étape dans un processus d’élaboration d’un modèle dynamique du développement de D. plantaginea à l’échelle du rameau, prenant en compte le rôle des fourmis et des auxiliaires et l’influence des pratiques de protection (par exemple, les filets Alt’Carpo et les lâchers d’auxiliaires). Elle confirme, si besoin en était, la complexité des phénomènes de régulation, des pucerons en particulier, et la nécessité d’études complémentaires pour définir les conditions d’application de la lutte biologique contre D. plantaginea / In the current political and social context (reduced use of pesticides), there is a need for the development of alternative solutions to control the rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera : Aphididae), especially in organic farming. One of these alternatives is the increased and improved use of natural enemies against this pest. In this thesis, we provided some elements of responses regarding this problem in term of research study and technical application. Based on weekly observations of arthropods in marked shoots infested by D. plantaginea, we demonstrated the negative effects of the natural enemies on the development of D. plantaginea but this effect was unsufficient to provide an effective regulation avoiding economic damages. We also showed the possible and positive influence of ant presence on the infestation dynamics and thei rnegative effect on natural enemies. Among the natural enemy groups, three were the most abundant and appeared in a temporary sequence : syrphids arrived first, at the beginning of the infestation,followed by coccinellids and earwigs that arrived later.To enhance the role of the natural enemies against D. plantaginea, we also need other practices that enable to reduce significantly the number of pesticide applied. This is the case of a very recent innovation : the Alt'Carpo nets. Despite its negative influence on the abundance and richness of the natural enemies, especially the coccinellids, present in the colonies of D. plantaginea, there was a negative influence of these nets on the development of D. plantaginea populations (both at the shootand tree levels) especially when the nets were closed in mid-April (coinciding with classical netting trees for controlling populations of codling moth). We additionally showed that the highest reductionin D. plantaginea population was observed in the presence of at least one active natural enemy in the marked shoot. This gives support to the combination of these methods of control, one biological and the other physical, to regulate D. plantaginea populations. Based on their precocity for Episyrphus balteatus De Geer (Diptera : Syrphidae) and their abundance for both Forficula auricularia Linnaeus (Dermaptera : Forficulidae) and E.balteatus observed under field conditions, the syrphids and earwigs appear as good candidates for controlling the D. plantaginea populations. We first demonstrated under laboratory conditions using detached plantain leaves in Petri dishes conditions the potency of these two predators, especially a tolder stages, against D plantaginea. The optimal predation occurred at 20°C for both predators. Using young apple trees, we further studied the possible interactions between these predators and showed a small and positive interaction when the D. plantaginea density was not limiting. But at low densities of aphids, the results suggested a possible negative interaction (a sign of intraguild predation) between these two predators. These results from laboratory studies have led us to study the augmentative release of these two predators, under field conditions, in early spring for controlling D. plantaginea populations. The releases of F. auricularia (third instar nymph) did not result in lower D. plantaginea populations. This confirmed the difficulty of successful releases of natural enemies under theconditions of open orchards, and demonstrated the need for improving or creating conditions that canpromote the success of the released natural enemies. However, despite closed conditions, the early release of E. balteatus under Alt'Carpo nets was also not efficient against D. plantaginea.This thesis, through several studies under different conditions (controlled, semi-field and field), represented an important first step that should ideally lead to the development of a dynamic model of the development of D. plantaginea at the shoot level, taking into account the presence of ants and therole of natural enemies and the influence of some agricultural practices (for example Alt'Carpo nets and natural enemy releases). Further studies are also needed to validate our results (effects of Alt'Carpo nets) and to optimise the releases of natural enemies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The experiment was carried out to evaluate the herbage production, sward structure, stocking rate, weight gain per area and nutritive value of forage as grazed in alexandergrass (Urochloa plantaginea (Link) Hitch) pasture fertilized with nitrogen (N). The experimental design was completely randomized following a repeated measurements arrangement. The treatments were 0; 100; 200 or 300 kg/ha of N. The experimental animals were Angus heifers with initial age and body weight of 15 month and 241.5±5 kg, respectively. The grazing method was continuous stocking with variable number of animals. The N utilization regardless of the amount increases 25% the daily herbage accumulate rate. The N fertilization increases 23% the weight gain per area. The quantity of 97.2 kg/ha of N allows greater leaf mass and increases in 20% the leaf:steam ratio. The alterations in sward structure changes the nutritive value of forage as grazed. The utilization of 112.7 kg/ha of N allows higher stocking rate (2049.8 kg/ha of BW) equivalent to 7.5 heifers per hectare. / Objetivou-se estudar a produção de forragem, estrutura do dossel, taxa de lotação, ganho de peso por área e o valor nutritivo da forragem aparentemente consumida por bezerras de corte em pastagem de papuã (Urochloa plantaginea (Link) Hitch) adubada com nitrogênio (N). O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo. Os tratamentos foram 0; 100; 200 ou 300 kg/ha de N. Os animais experimentais foram bezerras da raça Angus com idade e peso iniciais de 15 meses e 241±5 kg, respectivamente. O método de pastejo foi contínuo, com número variável de animais. A utilização de N, independente da quantidade, aumentou em 25% a taxa de acúmulo de forragem. A adubação com N proporciona aumento de 23% no ganho de peso por área. A dose de 97,2 kg/ha de N proporciona maior massa de lâminas foliares e aumento de 20% na razão folha:colmo. As alterações na estrutura do dossel modificam o valor nutritivo da forragem aparentemente colhida pelas bezerras. A dose de 112,7 kg/ha de N permite a manutenção da maior taxa de lotação (2049,8 kg/ha de PC), equivalendo a 7,5 bezerras por hectare.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The dry matter intake, ingestive behavior and displacement patterns were evaluated on beef heifers exclusively on pasture or receiving oats grain daily ( frequent ) or from Monday to Friday ( infrequent ) in "Vegetative" and "Reproductive" phenological stages of Alexandergrass (Urochloa plantaginea Link.). The grazing method was continuous with a variable number of animals. The experimental design was completely randomized, in a factorial 3 x 2 arrangement (three supplementation frequency and two phenological stages). Forage intake was estimated using chromium oxide as an indicator of fecal output. Forage intake was greater for heifers exclusively on pasture and daily supplemented (2.91% of body weight (BW)) than for heifers receiving infrequent supplementation (2.00% of BW). Forage intake was greater in "Vegetative" than "Reproductive stage. Changes in supplementation frequency and phenological stages of Alexandergrass caused variation in the use of feeding stations. The grazing time was diminished and the bites were heavier when heifers received daily supplementation. The bite weight and grazing time were similar in phenological stages while the bite rate decreased in the reproductive stage. Changes in supplementation frequency and in phenological stages of alexandergrass modify the feeding behavior and forage intake of beef heifers. / Nos estádios fenológicos Vegetativo e Reprodutivo do papuã (Urochloa plantaginea Link.) foram avaliados a ingestão de matéria seca, comportamento ingestivo e padrões de deslocamento de novilhas só em pastejo ou recebendo grão de aveia diariamente (frequente) ou de segunda a sexta-feira (infrequente). O método de pastejo foi continuo com número variável de animais. O delineamento experimental foi inteiramente casualizado, arranjado em esquema fatorial 3 x 2, três frequências alimentares e dois estádios fenológicos. A ingestão de matéria seca foi estimada por meio de técnica do óxido de cromo como indicador da produção fecal. Animais em pastagem exclusiva de papuã e com suplemento diário consumiram mais forragem (2,91% do PC em MS) que os animais que receberam suplemento de forma infrequente (2,00% do PC em MS). O consumo de forragem foi maior no estádio Vegetativo que no Reprodutivo . O uso das estações alimentares é modificado em resposta as frequências de suplementação e aos estádios fenológicos. Novilhas que receberam suplemento diariamente pastejaram por menor tempo e colheram bocados mais pesados. O peso de bocado e o tempo de pastejo foram semelhantes nos estádios fenológicos do pasto enquanto a taxa de bocado diminuiu no estádio reprodutivo.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Heifers rearing is a determinant step of efficiency in beef cattle production systems on pastures. Several experiments have tested alternative uses for tropical grasses to heifers rearing. In order to summarize results and making not visible relationships evident in these individual experiments an analysis was performed in a set of data from six experiments dealing with beef heifers rearing from 15 to 18 months of age on Pearl Millet (Pennisetum americanum), Alexandergrass (Urochloa plantaginea) and Coastcross (Cynodon dactylon) pastures. Canopy structure, herbage intake patterns, performance and body development of heifers were studied. Forage mass (3,000.4 kg DM/ha) and leaf blade mass (668.1 kg DM/ha) were similar between pastures while leaf blade: stem ratio of sward vertical strata was different. In Pearl Millet, higher forage allowance and canopy height were observed as well as less stems mass. The leaf blade allowance was higher in Pearl Millet (4.4%), intermediate in Alexandergrass (2.8%) and lower in Coastcross (1.8%). The daily intake of DM was lower in Coastcross (5.6 kg) compared to Alexandergrass (6.5 kg) and these values were similar to the value in Pearl Millet (6.1 kg). The bite mass and biting rate were similar in Pearl Millet and Alexandergrass. The main compensatory mechanism for smaller bite masses and reduced intake rates in Coastcross was increasing grazing time. The biting rate variations happened as a response to constraints imposed by the canopy architecture. Surface utilization on Alexandergrass and Coastcross was increased by the searching for leaf blades which influenced the increase of the number of feeding stations visited and displacement rate. Average daily gain was similar in Pearl Millet and Alexandegrass (0.864 kg) and less in Coastcross (0,610 kg). Daily weight gain per area was higher in Pearl Millet (8.1 kg/ha/day), which resulted in a higher production of total body weight (668.0 kg/ha). The body weight gain was mainly determined by forage mass and neutral detergent fiber in the three pastures. Body weight, body condition score, reproductive tract score, pelvic area and hip height were similar among heifers in the three grasses at 18 months of age. It suggests an adequate body development of heifers for mating at the end of pastures occupation, when the animals are at 18 months of age. To beef heifers rearing (from 14 to 18 months of age), Coastcross and Alexandergrass pastures are alternatives to Pearl Millet pasture. / A recria das novilhas constitui uma etapa determinante da eficiência dos sistemas de produção de bovinos de corte a pasto. Diversos experimentos têm testado alternativas de uso de gramíneas tropicais na recria de novilhas. Com o objetivo de sumarizar resultados e evidenciar relações não visíveis nestes experimentos individuais, foi realizada análise conjunta de dados provenientes de seis experimentos (n=436) que envolveram a recria de novilhas de corte, dos 15 aos 18 meses de idade, em pastagens de milheto (Pennisetum americanum), papuã (Urochloa plantaginea) e Coastcross (Cynodon dactylon). Foi analisada a estrutura do dossel, os padrões de ingestão de forragem, o desenvolvimento corporal e do trato reprodutivo das novilhas. A massa de forragem (3000,4 kg MS/ha) e de lâminas foliares verdes (668,1 kg MS/ha) foram similares entre as espécies forrageiras enquanto a relação lâmina foliar:colmo nos estratos verticais da pastagem foram diferentes. Houve maior oferta de forragem e altura do dossel e menor massa de colmos na pastagem de milheto. A oferta de lâminas foliares foi maior em milheto (4,4%), intermediária em papuã (2,8%) e menor em Coastcross (1,8%). A ingestão diária de MS foi menor em Coastcross (5,6 kg) em relação à papuã (6,5 kg) e esses valores foram similares à milheto (6,1 kg). A massa e a taxa de bocados foram similares em milheto e papuã, e menores em Coastcross. O aumento do tempo de pastejo foi o principal mecanismo compensatório da menor massa de bocados e reduzida taxa de ingestão em Coastcross. A variação na taxa de bocados foi uma resposta às limitações impostas pela estrutura do pasto. A busca por lâminas foliares ocasionou o aumento da exploração da área em papuã e Coastcross, com maior número de estações alimentares visitadas/minuto e maior taxa de deslocamento. O ganho médio diário foi similar em milheto e papuã (0,864 kg) e menor em Coastcross (0,610 kg). O ganho de peso por área foi maior em milheto (8,1 kg/ha/dia), o que resultou em maior produção total (668,0 kg/ha). Nas três espécies o ganho de peso corporal foi determinado principalmente pela massa de forragem e teor de fibra em detergente neutro do pasto do pasto. O peso corporal, escore de condição corporal e do trato reprodutivo, área pélvica e altura da garupa foram similares, nas três espécies forrageiras, aos 18 meses de idade das novilhas. Essas variáveis indicaram a possibilidade de acasalamento dos animais ao final do período de utilização das pastagens de verão, no sistema 18/20 meses de idade. Pastagens de Coastcross ou papuã constituem alternativas à pastagem de milheto para a recria de novilhas de corte dos 14 aos 18 meses de idade.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The animal performance, ingestive behavior and forage intake by beef heifers in Pearl millet (Pennisetum americanum (L.) Leeke) and Alexandergrass (Urochloa plantaginea) were studied. The experiment was carried out between January and April of 2008, in the Department of Animal Science of the Federal University of Santa Maria. The grazing method utilized was continuous with variable number of animals. Four animal testers, beef heifers Aberdeen Angus crossbreed, with average weight of 260 kg and 15 months old were used in each paddock. The put and take technique was used to keep the forage mass around three t/ha of dry matter. The experimental design was completely randomized with repeated measures in time, three replications for Pearl millet and five for Alexandergrass. The animal performance, patterns of ingestion (bite mass, bite rate), animal behavior (grazing, idle and rumination), chemical and morphologic composition of the forage and animal forage intake were evaluated as output variables. The forage intake was measured in the vegetative and reproductive phenological stages of the plants utilizing the technique of chromic oxide. The animals were dosified during twelve days and the feces were collected during six days in each period of evaluation. The animal behavior was studied by visual observation in four 24-hour continuous periods. The ingestive behavior and the intake rate were similar between species. The variables measured in the pasture had not presented correlation with the components of animal behavior. The daily average temperature was negatively correlated with grazing time. The herbage intake, of 2.49% of the body weight, the weight gain of 0.779 g/heifer/day and the stocking rate of 6.7 were similar in Pearl millet and Alexandergrass (P> 0.05). The total digestible nutrient content, the canopy height, the bite mass and the relative humidity presented high correlation with the herbage intake and can be used in the development of models to predict the performance of grazing animals. The utilization of Alexandergrass infested areas, with grazing animals, provides similar animal performance as in Pearl millet pasture. / Foram estudados o desempenho, comportamento e ingestão de forragem por novilhas de corte em milheto (Pennisetum americanum (L.) Leeke) e papuã (Urochloa plantagínea),de janeiro a abril de 2008. Foi utilizado o método de pastejo continuo com número variável de animais. O delineamento experimental foi o inteiramente casualizado com medidas repetidas no tempo. Foram avaliadas as seguintes variáveis-resposta: desempenho, padrões de ingestão (massa de bocado, taxa de bocados e número de bocados), comportamento (tempos de pastejo, ruminação, ócio), composição química e morfológica da forragem e ingestão de forragem. As avaliações de comportamento foram feitas por meio de observação visual, em quatro períodos contínuos de 24 horas. Os valores médios de massa de forragem, oferta de forragem e oferta de lâminas foliares foram de 3927 kg/ha de MS, 14,6 kg de MS/100 kg de PC e 3,36 kg de MS/100 kg de PC, respectivamente. As variáveis do pasto, desempenho animal, comportamento ingestivo e ingestão de forragem foram semelhantes em milheto e papuã (P>0,05). A ingestão de forragem foi de 2,49% do peso corporal. As variáveis da forragem, desempenho animal e tempos de pastejo, ócio e ruminação e número de bocados por dia, apresentaram variação ao longo dos dias de utilização da pastagem (P<0,05). A média de ganho médio diário foi 0,799 kg/dia, e foi limitado pela ingestão de energia. A pastagem de papuã permite obter ganhos individuais e taxas de lotações semelhantes à pastagem de milheto. Em áreas infestadas com capim papuã, sua utilização em pastejo proporciona desempenho semelhante ao do milheto.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / The work was developed with the objective to evaluate the intake of forage and beef heifers performance from 15 to 18 months old, grazing in Alexandergrass (Urochloa plantaginea (Link) Hitch) under rotational grazing method, receiving rice bran (FAI) as a supplement, at different levels (0, 0.5 and 1.0% of body weight (BW)). The experimental design was completely randomized with repeated measures over time. The use of FAI increased the total intake of dry matter (DM), total intake of crude protein and total digestible nutrients in relation to heifers exclusively on pasture. The heifers that received 1.0% PC FAI reduced the intake of forage DM increasing by 18% stocking rate (SR) and 27% BW gain per hectare (BWA) compared with the system exclusively in pasture. In the system in which the heifers received FAI at 0.5% of BW the SR and BWA were similar to other systems. In this feed system daily weight gain 18% higher than heifers exclusively on pasture and similar gain to the use of FAI at 1.0% of BW were observed. In Alexandergrass pasture under rotational grazing, using FAI at 0.5% of BW for beef heifers from 15 to 18 months of age is recommended to promote higher production response when compared to heifers exclusively on pasture and similar production when provided FAI at 1.0% of BW. / O trabalho foi desenvolvido com o objetivo de avaliar o consumo de forragem e o desempenho de novilhas de corte dos 15 aos 18 meses de idade, em pastejo em papuã (Urochloa plantaginea (Link) Hitch), sob método rotativo de pastejo, recebendo farelo de arroz integral (FAI) como suplemento, em diferentes níveis (0, 0,5 e 1,0% do peso corporal (PC)). O delineamento experimental foi o inteiramente casualizado, com medidas repetidas no tempo. O uso de FAI aumentou o consumo total de matéria seca (MS), consumo total de proteína bruta e de nutrientes digestíveis totais em relação às novilhas exclusivamente em pastejo. O consumo total de fibra em detergente neutro foi similar nos diferentes sistemas alimentares. As novilhas que receberam 1,0% do PC de FAI reduziram o consumo de MS da forragem, aumentando em 18% a taxa de lotação (TxLot) e em 27% o ganho de PC por hectare (GPA) em comparação com o sistema exclusivamente a pasto. No sistema em que as novilhas receberam 0,5% do PC de FAI a TxLot e o GPA foram similares aos demais sistemas. Nesse sistema alimentar foi observado GDM 18% superior em relação as novilhas exclusivamente em pastejo e ganho similar ao uso de 1,0% do PC de FAI. Em pastagem de papuã, sob pastejo rotacionado, é recomendado o uso de 0,5% do PC de FAI para novilhas de corte dos 15 aos 18 meses de idade, por promover respostas produtivas superiores em relação as novilhas exclusivamente em pastejo e semelhantes as observadas quando fornecido 1,0% do PC de FAI.