Difante, Gelson dos SantosRoberto, Francisca Fernanda da Silva2018-05-102018-05-102018-02-22ROBERTO, Francisca Fernanda da Silva. Avaliação de ovinos naturalmente infectados por nematoides gastrintestinais sob pastejo intermitente em cultivares de Brachiaria brizantha. 2018. 76f. Dissertação (Mestrado em Produção Animal) - Universidade Federal do Rio Grande do Norte, Universidade Federal do Rio Grande do Norte, Natal, 2018.https://repositorio.ufrn.br/jspui/handle/123456789/25172The aim of this study was to evaluate the response of sheep naturally infected by gastrointestinal nematodes, under intermittent grazing, in different Brachiaria brizantha cultivars. The experiment was carried out in the Experimental Area of the Group of Forage Research, located at the Macaíba Campus of the Federal University of Rio Grande do Norte. The experimental period was from 03/31/17 to 08/31/2017, which corresponded to two cycles of grazing. The animals were kept in a semi-intensive system with intermittent grazing and supplemented. We used 48 sheep, with no defined racial pattern, with a mean initial weight of 19.04 kg  0.96, randomly distributed in four pickets composed by Marandu, Xaraés, Piatã and Paiaguás. The experimental design was a randomized block design with 12 replicates in the animals and two blocks of the cultivars. The phenotypic variables evaluated weekly were: egg count per gram of feces (EPG), coproculture, globular volume (GV), anemia degree, weighing and body condition score (BCE). The recovery of infective larvae in the pasture and in the soil, were according to the exchange of the animals in the pre and post grazing pickets. The B. brizantha cultivars evaluated influenced the parasitic load of the animals, which were mixed and massive with values above 600 eggs/g independent of the grazed cultivar, with a significant difference in these values between the cultivars, ranging from 635.71 eggs/g (Xaraés) at 1422.2 eggs/g (Marandu). Among the grazing cycles, there were differences in the EPG of the animals kept in the Marandu cultivar (999.1 and 1422.2), being the largest in relation to the others. In the coproculture were found the genera Haemonchus sp., Trichostrongylus sp., Strongyloides sp., and Oesophagostomum sp. Haemonchus sp. was the most prevalent genus (over 80%) in all cultivars and grazing cycles. In the first grazing cycle, there was difference in GV of the animals kept in the Piatã (25.96%) and Xaraés (22.51%) cultivars, and those maintained in the other cultivars showed intermediate values. As to the degree of anemia, the animals remained more frequently in grades 1, 2 and 3, in order of importance in cycle 1, but in cycle 2, the concentration with more than 50% of the individuals was in grade 1. Regarding weight of the animals, that kept in the Xaraés cultivar differed from the others (P <0.05), with lower mean values in both cycles (21.79 and 26.91 kg). The BCE of the animals was concentrated at 3 in the first grazing cycle and at 3, 4 in the second cycle. The cultivars Marandu and Paiaguás presented the highest averages of larvae in the pasture. The highest concentration of larvae was found in pre-grazing and in the lower portion. It was possible to recover free-living and infecting stage larvae of the genera Haemonchus, Trichostrongylus and Strongyloides. In the soil samples of all cultivars, free life larvae and infective larvae of the genera Haemonchus and Trichostrongylus were recovered. The cv. Marandu presented higher averages of free-living larvae (5.37) and Haemonchus (0.53). In the first grazing cycle there was a higher nematode count in the soil samples, when compared to the second, except for cv. Marandu. It can be concluded that B. Brizantha cultivars promoted distinct conditions for the development and survival of the gastrointestinal nematodes present in the environment according to the morphological characteristics. The cultivars Piatã and Xaraés promoted smaller contaminations in the pasture and lower parasitic loads in the environment and in the animals, but Marandu and Paiaguás, provided better nutritional conditions to the animals, without compromising the phenotypic variables due to the higher parasitic load. The cultivars of Brachiaria brizantha Piatã, Xaraés, Marandu and Paiaguás should be recommended for pasture systems.Acesso AbertoCoproculturaHaemonchus sp.OvinoculturaPastagemTrichostrongylus spmasterThesisCNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PRODUCAO ANIMAL