Made available in DSpace on 2014-12-17T15:34:47Z (GMT). No. of bitstreams: 1 AlbertoLFAJ_DISSERT.pdf: 1671046 bytes, checksum: 8699a01f6b8beb7c7731350f466df41d (MD5) Previous issue date: 2013-04-10 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The control of gastrointestinal nematodes of small ruminants is usually done with anthelmintics. However, due to the emergence of ever-increasing parasite resistance to these drugs, looking up an alternative control parasites. One of this is sought in pasture management, as these are the sources of animals` infection by L3 infective larvae of helminths. The aim of this study was to evaluate the performance of sheep to natural infections by gastrointestinal nematodes grazing Panicum maximum cv. Massai and cv. Aruana, and Brachiaria brizantha cv. Piat? and cv. Marandu. The work was conducted from May to August-2011 with 48 male sheeps SRD versus Santa In?s breed. The animals were naturally infected with gastrointestinal nematodes, and maintained in four different cultivars of tropical forage grasses, naturally contaminated with eggs and larvae of gastrointestinal nematodes. Each week the animals were phenotypically characterized by parasitological examinations (eggs per gram of feces - EPG, and feces culture), hematological (packed cell volume PCV, and blood eosinophil count) method to evaluate the Famacha? colorof ocular mucosa, and the measures of body condition score and weight. In pastures was made the recovery of infective larvae in order to determine the quantity of L3 present in the pasture. The experimental design was a randomized completed block with two replications and before the entry of animals in the paddocks, they have been wormed. The experiment was ended when the animals reached 32.0 kg liveweight, and then were slaughtered and autopsies performed for the recovery and identify parasites of the abomasum, small intestine and large intestine. Results were subjected to analysis of variance, t test and Tukey`s test. The animals kept on pastures of Marandu grass had lower EPG counts, higher percentage of packed cell volume and higher average weight; those who remained in the Piat? pasture had lower eosinophil counts per microliter of blood. About the Famacha?, the highest prevalence was Famacha 2, and the body condition score ranged between 2 and 3. The results of feces cultures and recovery of larvae on pastures showed the presence of larvae of Trichostrongylus sp., and at the necropsy too. This way, it was concluded that the grass cultivars influences the sheep parasite load; the Famacha, together with EPG and packed cell volume are important indicators for use in controlling gastrointestinal nematode infections. The Trichostrongylus sp. was the most prevalent parasite in sheep during the rainy season / O controle dos nematoides gastrintestinais de pequenos ruminantes usualmente ? feito pela administra??o de anti-helm?nticos. Por?m, devido ao aparecimento cada vez mais crescente da resist?ncia parasit?ria a estas drogas, busca-se um controle alternativo e eficaz para as parasitoses. Uma das alternativas est? no manejo das pastagens, j? que estas s?o as fontes de infec??o dos animais pelas larvas infectantes L3 dos helmintos. Assim, o objetivo deste trabalho foi avaliar o desempenho de ovinos frente ?s infec??es naturais por nematoides gastrintestinais mantidos em pastagens de Panicum maximum cv. Massai e cv. Aruana, e Brachiaria brizantha cv. Piat? e cv. Marandu. O experimento foi realizado de Maio a Agosto/2011, com 48 ovinos machos, mesti?os SRD x Santa In?s, naturalmente infectados por nematoides gastrintestinais e mantidos em quatro diferentes cultivares de gram?neas forrageiras tropicais naturalmente contaminadas por ovos e larvas de nematoides gastrintestinais. Semanalmente, os animais foram caracterizados fenotipicamente atrav?s de exames parasitol?gicos (ovos por grama de fezes OPG e coprocultura), exames hematol?gicos (volume globular VG, e contagem de eosin?filos sangu?neos), pelo m?todo Famacha? para avaliar a colora??o da mucosa ocular, e pelas medidas de escore de condi??o corporal e ganho de peso. Nas pastagens foi feita a recupera??o das larvas infectantes, a fim de determinar a quantidade de L3 presentes no pasto. O delineamento experimental usado foi o de blocos casualizados com duas repeti??es, e antes da entrada dos animais nos piquetes, os mesmos foram vermifugados. O per?odo experimental foi finalizado quando os animais atingiram 32,0 kg de peso vivo, e em seguida foram abatidos e realizada a necr?psia para recupera??o e identifica??o dos parasitos do abomaso, intestino delgado e intestino grosso. Os resultados obtidos foram submetidos a an?lise de vari?ncia, teste t e teste de Tukey. Os animais mantidos nas pastagens de capim Marandu apresentaram menores contagens de OPG, maior porcentagem de volume globular e maior m?dia de peso; os que permaneceram na pastagem Piat? apresentaram menores contagens de eosin?filos por microlitro de sangue. O Famacha de maior preval?ncia foi o Famacha 2 e o escore de condi??o corporal oscilou entre os ?ndices 2 e 3. Os resultados das coproculturas e a recupera??o das larvas nas pastagens evidenciou presen?a de larvas de Trichostrongylus sp., bem como na necropsia este tamb?m foi o parasito de maior preval?ncia. Portanto, pode-se concluir que a cultivar forrageira influencia na carga parasit?ria dos ovinos; o Famacha, juntamente com o OPG e VG constituem indicadores importantes para serem utilizados no controle das verminoses gastrintestinais; o Trichostrongylus sp. foi o parasito de maior preval?ncia nos ovinos no per?odo chuvoso