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This study was designed to assess the influence of genetic resistance against brachiaria poisoning in sheep. Two groups of sheep, one identified as susceptible (formed by two ewes and one ram) and the other as resistant against brachiaria poisoning (formed by three ewes and one ram) were selected. Sheep considered susceptible were those that presented clinical signs of brachiaria poisoning at any time of their life; resistant sheep were those that even raised on Brachiaria spp. pastures, did not developed any sign of the poisoning during their life. The offspring of the two flocks (15 lambs from the sensitive flock and 9 lambs from the resistant flock) were placed into brachiaria pasture (initially Brachiaria decumbens and B. brizantha,and only B. decumbens after weaning) and followed up during two years (2013)(2014). The determination of protodioscin levels in B. decumbens pasture was performed only in 2014 and revealed significant amounts of the toxic principle. Eleven lambs of the susceptible group were affected to some degree of brachiaria poisoning and six died; no lamb of the resistant group was affected. Clinical signs consisted of varying degrees of subcutaneous edema of the face and, erythema and loss of hair of the ears, crusts on the skin of ears, around the eyes and on planum nasale, scar deformation of the ears, and bilateral ocular discharge; affected lambs also sought for shadowy shelters and they were poor doers. Several sheep recovered from the condition and then relapsed. Necropsy findings in six lambs included pale mucous membranes, emaciation, dermatitis, scar deformation of the ears, large yellow livers with marked lobular pattern, and moderate infestation by Haemonchus contortus. Histologically the liver lesions were similar in all necropsied lambs but with varying degrees of severity; they were consistent with brachiaria poisoning and included architectural disruption of hepatocellular trabecula, clusters of foamy macrophages occasionally forming multinucleated giant cells, swollen and vacuolated hepatocytes, crystals or negative images of crystals in the biliary system, bilestasis, bile duct proliferation and lymphoplasmacytic infiltrate in portal triads. The skin lesions were those of photodermatitis and included epidermal necrosis, hyperkeratosis and dermal neutrophilic infiltrate. The results of this study allow to conclude that there is a genetic related resistance to brachiaria poisoning in sheep since the progeny of resistant sheep did not manifest the poisoning.

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The objective of this study was to evaluate the methods of collecting Brachiaria spp. (Simulated Grazing vs. Total Collection) for the determination of protodioscin concentrations and to monitor the intoxication in sheep susceptible and resistant to poisoning by Brachiariaspp. The collection of Brachiaria spp. was done through two different methods. The first one consisted in throwing a metallic square at 10 random picket points. The second was performed simulating, with the hands, the grazing behavior of sheep. The leaf blades obtained by the two methods were conditioned in a forced ventilation oven. The extraction and quantification of protodioscin from the dry milled plant material was done by reverse-phase high-performance liquid chromatography (HPLC). The collections were carried out at three stages of the life of experimental lamb (suckling, rearing, and finishing). The lambs were divided into resistant and susceptible to intoxication by Brachiaria spp. The criterion for a lamb to be considered sensitive was to present some clinical signs at some stage of its life. No significant differences were observed between the general averages of the two collections when the evaluation was done in the whole period. However, a significant difference was found at the onset of the clinical signs. The concentrations of protodioscin in this period were higher in Brachiaria spp. collected by the simulating grazing method. Both methodologies were efficient to determine the level of protodioscin in the pastures of Brachiaria spp. However, during the periods when the outbreaks occurred, the simulated grazing method was more reliable.

This study aimed to evaluate the nutritional value of Urochloa exotic grasses to quantify aspects of antiquality and to identify their correlation with quality grasses. We evaluated the grasses U. humidicola cv. Comum, U. humidicola cv. BRS Tupi, U. decumbens cv. Basilisk, D70 U. decumbens and U. ruziziensis ecotype R124, and we grouped them into summer, autumn, winter and spring. We determined the chemical composition, in vitro digestibility, levels of protodioscin and cumulative gas production from the leaves of grass materials in nature. Basilisk and D70 showed higher content protodioscin in all seasons, with the highest values (31.4 and 27.4 g kg -1 , respectively) in spring. D70 had a crude protein content of 140.0 g kg -1 in summer and a better in vitro digestibility of dry matter (888.7 g kg -1 ). R124 had a higher cumulative gas production in the spring (16.44 mL gas 100 mg DM -1 ). U. humidicola (Comum and BRS Tupi) presented lower protodioscin concentrations (1.22 and 1.07 g kg DM -1 , respectively), and U. decumbens (Basilisk and D70) presented higher concentrations (27.25 and 24.55 g kg DM -1 , respectively). The presence of protodioscin interfered with in vitro digestibility results and cumulative gas production in vitro. Key words: Fodder. Gas production. In vitro digestibility. ResumoObjetivou-se avaliar o valor nutricional e quantificar os aspectos de anti-qualidade e suas correlações com a qualidade de gramíneas exóticas do gênero Urochloa. Foram avaliadas as gramíneas Urochloa. humidicola cv. Comum, Urochloa humidicola cv. BRS Tupi, Urochloa decumbens cv. Basilisk, Urochloa decumbens ecotipo D70 e Urochloa ruziziensis ecotipo R124 e agrupadas em épocas verão, 1 Projeto financiado pelo CNPq, (processo n° 563988/2010-0) e pela FUNDECT (processo 23/200.145/2011).

Five cultivars of Urochloa brizantha (Hochst. ex A.Rich.) R.D. Webster (syn. of Brachiaria brizantha) were evaluated for nutritional value and an anti-nutritional factor (protodioscin), in order to determine whether protodioscin content was correlated with reduced feed quality. We evaluated cvv. Arapoty, Paiaguas, Xaraes, Marandu and Piata and grouped the results into summer, autumn, winter and spring seasons. Protodioscin content and chemical composition of leaves, in vitro digestibility and cumulative gas production were analysed. Data were evaluated by analysis of variance as a completely randomised experimental design in a factorial arrangement (five cultivars × four seasons). There was no significant interaction between cultivar and season. All grasses showed highest protodioscin contents during autumn. Protodioscin contents ranged from 5.6 g kg–1 (spring) to 19.2 g kg–1 (autumn). Crude protein content varied significantly across seasons. No significant effect was detected for neutral detergent fibre (NDF) content among seasons. Cultivar Arapoty showed the highest NDF content in summer (669.3 g kg–1) and the lowest in spring (601.9 g kg–1). The best in vitro digestibility coefficients were observed in spring. The protodioscin content of U. brizantha cultivars can negatively affect their digestibility and some parameters of cumulative in vitro gas production.

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