ABSTRACT The goal of our study was to evaluate the nutritional potential of dented corn hybrids for silage production. We performed a two-location trial in which 19 dented corn hybrids and five corn controls grew in four randomized blocks within two experimental areas located in the Northern (Campos dos Goytacazes) and Northwestern (Itaocara) Rio de Janeiro State, Brazil. We recorded yields of fresh and dry forage matter and yields of fresh and dry grain matter, as well as chemical composition variables. We interpreted variables by assuming a Normal distribution for yield variables and a Beta distribution for chemical composition and ratios. The SAS GLIMMIX procedure fitted the linear model under those assumptions. Dual-pool models fitted the gas production profiles generated by in vitro anaerobic fermentations. We used the nlme of R software to fit the dual-pool models and the information-theoretic approach to evaluate their quality of fit. We did a cluster analysis (NbClust of R) to group corn hybrids based on fresh and DM yields and kinetic parameters of in vitro gas production. Three clusters of corn hybrids stood out, their basic differences relied on fresh and DM yields. Nonetheless, the least-squares means for gas production characteristics among groups did not present disjoint confidence intervals. Therefore, we can infer that dented corn hybrids rank by forage yield, but not by forage quality, and recommend the most productive ones that consistently outstand in both locations (hybrids UENF-2203, UENF-2192, UENF-2193, and UENF-506-11).

Abstract This study described the main characteristics of the maize cultivars UENF MSV2210 and UENF MS2208. Adapted to the North and Northwestern regions of the state of Rio de Janeiro, they have a high agronomic performance and were developed for both silage and green maize production.

ABSTRACT The aim of this study is to assess whether there is linear dependence between groups of morphoagronomic and bromatological traits in hybrid silage corn. Nineteen topcross hybrids and five checks were assessed in two different environments in Campos dos Goytacazes and Itaocara counties, Rio de Janeiro State, during the growing seasons 2013/2014. The study followed a randomized blocks design with four replicates. The phenotypic and canonical correlations between the groups of seven morphoagronomic and five bromatological traits were assessed. There is linear dependence between the group pairs of morphoagronomic, and bromatological variables. The morphoagronomic trait green mass yield can be adopted in indirect selection processes to indicate the increased bromatological quality of maize silage based on features such as crude protein, neutral detergent fiber, lignin, crude fat and mineral matter. Topcross hybrids UENF-2208 and UENF-2209 presented high potential for silage yield in the North and Northwest Regions.

RESUMO O objetivo deste trabalho foi avaliar quatro índices de seleção e o método BLUP na predição de ganhos genéticos em híbridos de milho para silagem. Foram comparados quatro índices de seleção e o método BLUP na predição de ganhos genéticos. Foram avaliados 19 híbridos topcrosses, e cinco testemunhas em delineamento experimental de blocos casualizados com quatro repetições em dois ambientes, nos municípios de Campos dos Goytacazes e Itaocara - RJ, no ano agrícola 2013/2014. Avaliaram-se as características altura de plantas, altura de inserção da primeira espiga, diâmetro do colmo, produtividade de grãos no ponto de silagem e produtividade de massa verde. Para predição de ganhos foram empregados os índices de seleção de Pesek & Baker, Smith & Hazel, Mulamba & Mock e Willians, além do método BLUP. Dentre os índices de seleção avaliados, o de Mulamba & Mock proporcionou maiores magnitudes na estimativa de ganhos para a seleção dos híbridos. O método BLUP mostrou-se eficiente, selecionando híbridos com desempenho elevado e superiores aos obtidos pelos índices de seleção testados. Os híbridos UENF-2205, UENF-2208, UENF-2209 e UENF-2210, foram os que apresentaram melhor desempenho indicando elevado potencial dos híbridos dentado para produção de silagem na região Norte e Noroeste Fluminense.

ABSTRACT The objective of this study was to evaluate four selection indexes and best linear unbiased prediction (BLUP) for predicting genetic gain in maize hybrids used for silage. The genetic gain was compared between four selection indexes and BLUP. Nineteen topcross hybrids and five controls were evaluated using a completely randomized block design with four replicates in two areas located in Campos dos Goytacazes and Itaocara, Rio de Janeiro, Brazil, in the growing season 2013-2014. Plant height, first ear height, average stem diameter, grain yield at the silage stage, and green mass yield were evaluated. The genetic gain was predicted using the selection indexes proposed by Pesek and Baker, Smith and Hazel, Mulamba and Mock, Willians, and BLUP. The index of Mulamba and Mock provided higher gain estimates for selecting hybrids. BLUP was efficient and selected hybrids with higher performance than hybrids obtained using the four selection indexes. Hybrids UENF-2205, UENF-2208, UENF-2209, and UENF-2210 presented better performance, indicating the high potential of these dent hybrids for silage production in the north and northwest regions of Rio de Janeiro.

RESUMO Este estudo objetivou avaliar o efeito da adubação com nitrogênio (N) e potássio (K) sobre o acúmulo o valor nutritivo da forragem da Urochloa ruziziensis, durante as estações de verão de 2010/2011 (verão 1), outono, inverno, primavera e verão de 2011/2012. Foi utilizado o delineamento em blocos completos casualizados com quatro tratamentos (0, 120, 240 e 360 kg ha-1year-1 de N e K2O) e cinco repetições. Os dados foram analisados pelo PROC MIXED do SAS®. Foram avaliadas as variáveis: altura do dossel, massa de forragem, densidade volumétrica da forragem; porcentagens de massas secas de lâminas foliares, colmos de material morto; relação lâmina: colmo; teores de matéria seca, proteína bruta e digestibilidade in vitro da matéria seca, fibra em detergente neutro, lignina da forragem da Urochloa ruziziensis. Houve efeito de interação entre doses de adubação com N e K e estação do ano para todas as variáveis. Também houve efeito linear positivo de doses de fertilização com N e K sobre a taxa de acúmulo de forragem, o teor de proteína bruta e da digestibilidade in vitro da matéria seca, e efeito linear negativo sobre os teores de fibra em detergente neutro e de lignina durante a primavera e o verão 2. A adubação com N e K e as mudanças climáticas características de cada estação afetam de forma conjunta o acúmulo e valor nutritivo da Urochloa ruziziensis. A adubação com N e K com até 360 kg ha-1ano-1 aumenta o acúmulo de foragem e o valor nutritivo de Urochloa ruziziensis.

ABSTRACT This study aimed to assess the effect of nitrogen (N) and potassium (K) fertilisation on the forage accumulation and nutritive value of Urochloa ruziziensis during the summer of 2010/2011 and autumn, winter, spring and summer of 2011/2012. A complete randomised block design with four treatments (0, 120, 240 and 360 kg ha-1 year-1 N and K2O) and five replicates were used. The data were analysed under the PROC MIXED of SAS®. The following variables were evaluated: sward height; forage mass; forage bulk density; percentages of leaf blade dry matter, stem dry matter, and dead material dry matter; leaf blade:stem ratio; contents of dry matter and crude protein; in vitro digestibility of dry matter; neutral detergent fibre content; and lignin content of Urochloa ruziziensis. There was an interaction between the N and K levels of fertilisation and the season for all variables. In addition, there was a positive linear effect of the N and K levels of fertilisation on the forage accumulation rate, the crude protein content and the in vitro digestibility of dry matter and a negative linear effect these levels on the neutral detergent fibre and lignin contents during the spring and summer of 2011/2012. N and K fertilisation and the climate changes characteristic of each season jointly affected the accumulation and nutritive value of Urochloa ruziziensis. N and K fertilisation up to 360 kg ha-1 year-1 improved the forage accumulation and nutritive value of Urochloa ruziziensis.

ABSTRACT This experiment was conducted to evaluate the degradation kinetics and microbial efficiency of beef cattle grazing on low-quality forage and receiving supplements with different levels of rumen undegradable protein (RUP). The animals grazed on palisade grass pasture solely or this pasture and supplement containing 40 or 60 g of RUP per 100 g of crude protein (CP). The degradation profiles of neutral detergent fiber, fiber carbohydrates, and neutral detergent insoluble protein were interpreted kinetically by using a decreasing logistic model. Treatments (no supplement, or RUP at 40 or 60 g−1 100 g CP) did not affect rumen fill; however, the increase in the indigestible fiber carbohydrate fraction that occurred at the expense of the digestible fiber carbohydrate fraction resulted in a greater rumen fill effect. The palisade grass showed a significant proportion of its nitrogen in the form of slowly degradable protein as neutral detergent insoluble protein, which amounted to 26 g per 100 g CP. Supplementation with 40 g of RUP per 100 g CP decresead the indigestible fraction of the low-quality forage. However, the absence of a rumen-fill effect demonstrates that the additional supply of nutrients contributes greatly to increasing growth efficiency and use of the available energy from the forage by the ruminal microorganisms.