The aim of this study was to evaluate the chemical composition, fractionation of carbohydrates and nitrogen compounds, degradation parameters, and in vitro ruminal fermentation of cactus pear genotypes. The experiment was conducted in a completely randomized design with 4 cactus pear genotypes and 4 replicates. The evaluated cactus pear genotypes were: Miúda (Nopalea cochenillifera Salm Dyck), IPA Sertânia (Nopalea cochenillifera), Gigante (Opuntia ficus indica Mill), and Orelha de Elefante Mexicana (Opuntia stricta Haw), all in natura. Samples were randomly collected at different points in the experimental area. Whole plants were collected 24 months after field crop establishment. N. cochenillifera Salm Dyck presented the highest dry matter, acid detergent insoluble protein, non-fibrous carbohydrate, total digestible nutrients, digestible energy, total carbohydrates, and fractions A + B1 (P<0.05), while presenting lower neutral detergent fiber corrected for ash and protein, acid detergent fiber, and cellulose in relation to the other genotypes studied (P<0.05). The in vitro true digestibility of neutral detergent fiber was high for the genotypes N. cochenillifera Salm Dyck and N. cochenillifera Dyck, which also presented high in vitro total gas production (P<0.05). The cactus pear genotypes show adequate chemical characteristics to be composed part of diets offered to ruminants. However, supplementation is necessary to increase the dry matter and fiber contents. The Nopalea cochenillifera Salm Dyck genotype presented the highest proportions of total digestible nutrients, non-fibrous carbohydrates, non-protein nitrogen, unavailable nitrogen fraction total, and high gas production in relation to the other analyzed genotypes 24 months after field crop establishment.

The experiment aimed at determining repeatability coefficients for four methods (analysis of variance, principal components-correlation and covariance matrices and structural analysis), number of harvests necessary to increase accuracy and phenotypic stability of yield characteristics of accessions of Panicum maximum. The experiment was conducted in a completely randomized design with 35 genotypes and three replications. Five cuts were made and material was weighed and dried to obtain total, stem, leaf and dead forage dry matter yields. The repeatability coefficients in the different methods, for the evaluated characteristics, ranged from 0.1867 and 0.6583. The estimates of repeatability coefficients obtained for the evaluated characteristics by analysis of variance were generally smaller than the ones obtained with the other methods. By the principal components (based on the covariance matrix), the estimates were usually larger than those for the other methods. Therefore, it is possible to recommend this method to estimate the coefficient of repeatability for traits evaluated in this study. Considering that levels of 80 or 90% of confidence in the evaluation of the relative superiority of the accessions for all the evaluated characteristics are satisfactory, five harvests are sufficient for the choice of the best accession.

This study aimed to evaluate the chemical and minerals composition, fractions of carbohydrate and nitrogen compounds, kinetics of degradation and in vitro gas production of native cactus species of the brazilian Semiarid. The experiment was conducted in a completely randomized design, with five native cactus species and 4 replications per species were randomly selected. The native cactus species evaluated were: Cereus jamacaru DC., Melocactus bahiensis Br. Et Rose Werderm, Opuntia inamoene K. Schum, Pilosocereus gounellei (A. Weber ex K. Schum) Bly ex Rowl and Pilosocereus pachycladus Ritter, all in natura. The native cactus species showed differences for chemical and mineral compositions (P <0.05). The nitrogenous components, C. jamacaru cactaceae presented higher contents of fractions A (228.1 g/kg CP) and B3 (241.7 g/kg CP) and smaller fraction C (174.0 g/kg CP). For carbohydrate fraction C. jamacaru presented lower fractions A + B1 (412.2 g/kg TC) and C (38.2 g/kg TC) and high fraction B2 (549.7 g/kg TC) and low fraction C. The cactus C. jamacaru and M. bahiensis presented a high PD (856.6 and 837.9 g/kg DM, respectively). The parameters a and b and the effective degradability present diferences (P<0.05) in function of 2% and 5% passage rate. The in vitro true digestibility of dry matter was above 700 g/kg of DM for all species. Cactus have high levels of potentially digestible fractions of total carbohydrates, indicating their importance as food for ruminants in created in the semiarid, where Caatinga vegetation is a basal resource.

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-This experiment was carried out with the objectives of determining repeatability coefficients, the number of harvests necessary to increase accuracy and the genotypic stability of yield characteristics in Brachiaria brizantha cultivars in the northeast region of Brazil in the period from July 2009 to March 2011. The experimental design used was completely randomized with three treatments (Brachiaria brizantha var. Marandu, Xaraés and Piatã) and three replications. Each plot was harvested seven times: five in the rainy season and two in the dry season. Immediately after each harvest, the forage was weighed and dried to obtain total, stem, leaf and dead dry matter yields. For the estimation of the repeatability coefficient, analysis of variance, principal components (correlation and covariance matrices) and structural analyses were used. The repeatability coefficients (r) obtained by the different methods, for all characteristics evaluated, varied from 0.009 to 0.837. The estimates of the repeatability coefficients obtained for all characteristics evaluated by the method of analyses of variance were almost always lower than those obtained by the other methods. By the principal components method (based on the covariance matrix), the estimates were always higher than those from other methods. Considering that levels of 80 or 90% confidence are satisfactory in the evaluation of the relative superiority of the cultivars for all the evaluated characteristics, with the exception of dead matter yield, the seven harvests are sufficient for the choice of the best cultivar to be used in the northeast region of Brazil.