Autor para correspondência. 2 Médico Veterinário, Professor, Doutor, DCTA, CCR, UFSM. -REVISÃO BIBLIOGRÁFICA -RESUMOA crescente restrição ao uso de drogas veterinárias como promotores de crescimento na nutrição animal fez com que surgisse uma nova geração de produtos para auxiliar no equilíbrio benéfico da microbiota do trato gastrintestinal (TGI), entre eles, os prebióticos. Prebióticos são compostos não digeridos por enzimas, sais e ácidos produzidos pelo organismo animal, mas seletivamente fermentados por microrganismos do TGI. Estes compostos podem atuar beneficamente sobre a modulação da microbiota nativa, sobre o sistema imune e sobre a mucosa intestinal, melhorando os processos de digestão e absorção dos nutrientes. Porém, a adição de compostos de potencial ação prebiótica às dietas nem sempre reflete-se da mesma forma sobre a resposta biológica, o que pode estar relacionado com a composição dos ingredientes presentes na dieta, com a dosagem adicionada, com a adaptação e a seletividade da microbiota ao prebiótico, ou com o nível de estresse do animal.Palavras-chave: microbiota intestinal, trato gastrintestinal, promotores de crescimento, oligossacarídios não digestíveis. ABSTRACTDue to the increasing constraint on the use of veterinary drugs as growth promoters in nonruminants nutrition there is a need to develop alternatives in supporting the microflora of the digestive tract in their approach to control pathogenic bacteria. The prebiotics are resistant compounds to digestion in the animal digestive tract, but selectively fermentable by intestinal microflora. These compounds can beneficially affect native microbiota, immune system and intestinal mucosal improving the digestion and absorption of nutrients. However, not always the use of the prebiotics causes alterations in the biological response. There may be several factors involved that partly explain the lack of response, such as: differences in the chemical composition of the ingredients of the diet, differences in the levels (percentage) of the prebiotics used in the diet, adaptation and the selectivity of the microflora and stress factors.

The term CLA (conjugated linoleic acid) corresponds to a mixture of positional and geometric isomers of linoleic acid. Two of these isomers (9c, 11t and 10t, 12c) have biological activity. The milk and dairy products are the most abundant source of conjugated linoleic acid, which refers to a group of positional and geometric isomers of CLA (CLA 18:2 cis-9, cis-12). The following research aims to approach aspects regarding the CLA, as well as its relationship with diseases. Conjugated linoleic acids have been studied for their beneficial effects in the prevention and treatment of many diseases, including obesity, cancer, diabetes, and cardiovascular diseases. Scientific information put together the physiological properties of CLA, which serves as inputs to claim their potential as functional ingredients to be used in the prevention and control of several chronic metabolic disorders.

Brewer's spent grain (BSG) could be tested as an alternative source of polyphenols in animal nutrition. Proper extraction and analytical methods are critical for quantification. Thus, extraction for BSG, corn silage, and brans of rice, corn, and wheat were studied for the highest yield of polyphenols. A method for 18 phenolic monomers by HPLC-DAD was developed, validated, and applied to samples. An aqueous solution of NaOH (0.75% w/v) using integral samples for extraction resulted in the highest values for colorimetric measurements in all analyzed sources. Method by maceration showed the highest phenolic yield when applied in corn silage and BSG. However, for brans the best method was microwave assisted. Results from HPLC-DAD analysis clearly showed that native structures of phenolic compounds were simplified to its monomers allowing quantification and sample discrimination. BSG had the highest concentration of polyphenols and could be a promising and innovative source for animal feed studies.

RESUMO -Esta pesquisa foi conduzida com o objetivo de avaliar a silagem de 12 genótipos de seis espécies de cereais de inverno de duplo propósito (forragem e grãos), submetidos ao corte na região da Depressão Central do Rio Grande do Sul. As espécies e os genótipos testados foram: trigo BRS 277, BRS Guatambu, BRS Tarumã, BRS Umbu; aveia-preta Agro zebu, UPFA 21 -Moreninha e Comum; aveia-branca UPF 18; centeio BR 1 e BRS Serrano; Cevada BRS Marciana; e triticale BRS 148. Os genótipos foram submetidos a três cortes com o objetivo de simular o pastejo, conforme manejo indicado para duplo propósito. Após o terceiro corte, permitiu-se o desenvolvimento das culturas para a ensilagem. As silagens foram feitas em silos experimentais de PVC quando as forrageiras atingiram o estádio fenológico de grão pastoso. O delineamento experimental foi o inteiramente casualizado, com 12 tratamentos (genótipos) e três repetições (parcelas). Foram determinadas a produção de matéria seca e a composição estrutural do material ensilado, o valor nutritivo e os parâmetros fermentativos das silagens. O centeio BR 1 e a aveiabranca UPF 18 apresentaram as maiores produções de matéria seca. O trigo BRS Umbu produziu silagem com maior participação de grãos e valor nutritivo mais elevado. Todos os genótipos apresentaram condições satisfatórias para a ensilagem.Palavras-chave: capacidade tampão, forragem conservada, integração lavoura-pecuária, proteína bruta Genotypes were submitted to tree harvests with the objective to simulate grazing, according to double purpose management.After the third harvest, the development of cultures was permitted for silage production. The genotypes were distributed in 36 experimental plots in a completely randomized experimental design with 12 treatments (genotypes) and three replications (plots). Silages were made in PVC experimental silos when forages achieved phenological stage of soft dough.Fermentative parameters, dry matter production, structural and botanical composition of ensilage material and nutritive value of silages were determined. BR 1 rye and UPF 18 white oat presented the highest dry matter yield. BRS Umbu wheat produced silage with higher grain participation and better nutritive value. All genotypes presented satisfactory conditions for ensilage.

RESUMO -Foi avaliado o desempenho de novilhos de corte, durante a fase de recria, em capim-elefante (Pennisetum purpureum Schum.) cv. Taiwan A-146, papuã (Brachiaria plantaginea (Link) Hitchc), sorgo forrageiro (Sorghum bicolor (L.) Moench) cv. AG 2501C e milheto (Pennisetum americanum (L.) Leeke) cv. comum. O período total de pastejo foi de 143 dias para a pastagem de capim-elefante e 98 dias para as demais pastagens. O sistema de pastejo foi o contínuo com lotação variável. O teor de proteína bruta na massa de forragem foi de 5,43; 10,08; 9,95; e 10,58% e a digestibilidade in vitro da matéria seca, de 50,93; 55,85; 54,56; e 54,81% para capim-elefante, papuã, sorgo e milheto, respectivamente. Houve diferença significativa no ganho de peso médio diário, que foi de 0,928; 1,054; 1,121; e 1,188 kg, para o capim-elefante, papuã, sorgo e milheto, respectivamente. Não houve diferença significativa na carga animal entre as pastagens, sendo de 1682, 1634, 1389 e 1514 kg de PV/ha, e no ganho de peso vivo, que foi de 774, 668, 570 e 640 kg de PV/ha para as pastagens de capim-elefante, papuã, sorgo e milheto, respectivamente. A utilização de pastagens cultivadas de verão, manejadas corretamente, permite altos ganhos de peso por animal e por área, constituindo-se em uma excelente alternativa para intensificar a produção de bovinos de corte.Palavras-chave: capim-elefante, milheto, papuã, pastejo, sorgo Animal Performance in Summer Grasses PasturesABSTRACT -The performance, during the summer of beef steers grazing elephantgrass (Pennisetum purpureum Schum.), alexandergrass (Brachiaria plantaginea (Link) Hitchc), sorghum (Sorghum bicolor (L.) Moench) and millet (Pennisetum americanum (L.) Leeke) was evaluated. The grazing period for the elephantgrass occurred from 12/04/93 until 04/26/94, and for the other grasses occurred from 01/04/94 until 04/12/94. The total period of grazing was of 143 days for the elephantgrass and of 98 days for the other pastures. The continuous grazing system with variable stocking rate was used. The crude protein of the forage mass was 5.43, 10.08, 9.95 and 10.58% and "in vitro" dry matter digestibility was 50.93, 55.85, 54.56 and 54.81% for elephantgrass, alexandergrass, sorghum and millet, respectively. Significant difference was observed for average daily weight gain which was .928, 1.053, 1.121 and 1.188 kg for elephantgrass, alexandergrass, sorghum and millet. No significant difference was observed for stocking rate (1,682, 1,634, 1,388 and 1,541 kg of live weight/ha) and for live weight gain which was 774, 668, 570 and 640 kg/ha for the pasture of elephantgrass, alexandergrass, sorghum and millet, respectively. The use of summer cultivated pastures with correct management, allows high weight gains per animal and per area, being an alternative for intensive beef cattle production.