ABSTRACT. The objective of this study was to evaluate the activity of invertases and amylases in Brachiaria brizantha cv. Marandu under various shade and nitrogen fertilization conditions. The experiment was carried out in a greenhouse using a 4 x 2 factorial scheme (shading levels of 0, 30, 50, and 80% and fertilization with 0 and 100 kg N ha-1). The activity of the enzymes, cytosol-neutral invertase (Inv-N), vacuole acid (Inv-V) and cell-acidic acid (Inv-CW), reducing sugars (RS), and α and β-amylases were evaluated (α = 0.05). The interaction was significant for Inv-N within the leaf. In the first cycle, the highest activity was in fertilized plants with 30, 50, and 80% shading. For Inv-CW in the 1st cycle, the highest activity occurred with 0, 30, and 50% shading. However, the interaction for Inv-V leaf activity was not significant in the 1st and 2nd cycles. The highest activity observed for Inv-V was in the fertilized plants, suggesting that fertilization increased the enzymatic activity. The activity of the invertases increased both under 30-50% shaded conditions and in full sun. Furthermore, invertase activity was directly linked to the osmoregulatory system. The reduction in RS was related to a low photosynthetic rate, and an increase α and β-amylase was associated with the use of reserve energy sources to meet energetic needs.

ABSTRACT. The objective of this study was to verify the activity of invertases in Estilosantes under the influence of cultivation systems and nitrogen fertilization in two seasons. The experiment was conducted in the Xaraés area, where Estilosantes was planted according to a 2 x 2 factorial scheme with two cultivation systems (monoculture and mixed pasture) in the absence or presence of fertilization (75 kg of N ha-1). A randomized block design with four replications was used. The neutral cytosol (Inv-N), vacuole acid (Inv-V) and cell wall acid (Inv-CW) invertase activity and reducing sugar contents in the leaves and stems were evaluated and analyzed by a 5% probability F-test. The interaction between cultivation systems and nitrogen fertilization was significant for Inv-N in the leaves in the summer, such that greater activity occurred in response to the mixed pasture system and nitrogen fertilization. Nitrogen increased the activity of the Inv-N in the stem in both periods, increased the activity of Inv-V in the leaf in the summer, and decreased the activity of Inv-CW in the fall. This cultivation system influenced the activity of Inv-N regardless of the period of the year and did not interfere with the activities of the acid invertases. The invertases did not show regular changes in relation to nitrogen fertilization.

RESUMO. Objetivou-se selecionar genótipos de sorgo para produção de silagem. O estudo foi conduzido no campo experimental da Embrapa Milho e Sorgo. O plantio foi realizado em blocos casualizados, com três repetições e teste Scott-Knott em nível de 5% de probabilidade. O material foi ensilado em silos laboratoriais, abertos com 56 dias para realização das análises fermentativa e composição bromatológica. Somente a proteína bruta não apresentou diferença significativa (p > 0,05), com média geral de 8,88%. As demais variáveis apresentaram diferenças significativas (p < 0,05):pH (3,34 a 3,94); Aw (0,93 a 0,98); N-NH3/NT (1,61 a 6,56 %); produção de matéria verde (12,05 a 34,14 t ha-¹); produção de matéria seca (6,19 a 11,42 t ha-¹); matéria seca (26,89 a 49,95 %); cinzas (4,08 a 6,88 %); fibra em detergente neutro corrigido para cinzas e proteínas (47,67 a 65,79 %); fibra em detergente ácido (16,62 a 35,89%); hemicelulose:celulose (1,07 a 2,71 %); lignina (2,03 a 6,52 %), produção de matéria seca digestível (3,70 a 7,41 t ha-¹) e digestibilidade da matéria seca (56,36 a 72,67%). Com base na produção de matéria seca digestível, os genótipos: macho 201191, e os híbridos 2012F47484, 2012F47515 e 2012F47525 se sobressaíram em relação aos demais uma vez que apresenta boa produtividade, adequado valor nutricional, com baixos teores de matéria seca e FDN aliado com altos valores de digestibilidade e bom padrão fermentativo das silagens.

ABSTRACT. The objective of this study was to select sorghum genotypes for silage production. The study was carried out at Embrapa Maize & Sorghum’s experimental field. Planting was performed in randomized blocks, with three replicates and the Scott-Knott test at a 5% probability level. The material was ensilaged in laboratory silos opened after 56 days for analysis concerning fermentation and bromatological composition. Only crude protein showed no significant difference (p > 0.05), with an overall mean of 8.88%. The other variables presented significant differences (p < 0.05): pH (3.34 to 3.94); Aw (0.93 to 0.98); N-NH 3/TN (1.61 to 6.56%); green matter yield (12.05 to 34.14 t ha-1); dry matter yield (6.19 to 11.42 t ha-1); dry matter (26.89 to 49.95%); ashes (4.08 to 6.88%); neutral detergent fiber corrected for ash and protein (47.67 to 65.79%); acid detergent fiber (16.62 to 35.89%); hemicellulose:cellulose (1.07 to 2.71%); lignin (2.03 to 6.52%), digestible dry matter yield (3.70 to 7.41 t ha-1) and dry matter digestibility (56.36 to 72.67%). Based on digestible dry matter yield, the genotypes: male 201191 and hybrids 2012F47484, 2012F47515 and 2012F47525 stood out in relation to the others for showing good yielding, adequate nutritional value, with low dry matter and NDF levels coupled with high digestibility values and good fermentation patterns of the silages.

RESUMO Objetivou-se selecionar dentre 24 genótipos de sorgo os superiores para produção de silagem. O estudo foi conduzido no campo experimental da Embrapa Milho e Sorgo, município de Sete Lagoas, Estado de Minas Gerais. Utilizados 24 genótipos de sorgo forrageiro, 21 híbridos do cruzamento entre fêmeas graníferos e machos forrageiros (12F38019, 12F38006, 12F40006, 12F40005, 12F40019, 12F37016, 12F37005, 12F37043, 12F39006, 12F39005, 12F39019, 12F38005, 12F38007, 12F37007, 12F39007, 12F40007, 12F38014, 12F37014, 12F39014, 12F40014 e 12F38009) e três testemunhas: BRS 610, BRS 655 e Volumax. Estimada a produtividade por área, digestibilidade in vitro da matéria seca, características bromatológicas e fermentativas das silagens de sorgo. A digestibilidade in vitro da matéria seca, proteína indisponível em detergente neutro, fibra em detergente neutro corrigido para cinzas, proteína, fibra em detergente ácido, hemicelulose e lignina foram diferentes quanto aos genótipos testados. O pH e nitrogênio amoniacal das silagens também apresentaram diferenças entre genótipos. A maioria dos genótipos testados é favorável à produção de silagem, exceto o híbrido com maior teor de lignina 12F370014 e os híbridos 12F37007 e 12F370014, que apresentaram os maiores valores de FDNcp.

ABSTRACT The objective was to select from among 24 sorghum genotypes the superior ones for silage production. The study was conducted in the experimental field of Embrapa Maize & Sorghum, in the municipality of Sete Lagoas, Minas Gerais State. It used 24 forage sorghum genotypes, 21 being hybrids from the crossing of grain sorghum females and forage males (12F38019, 12F38006, 12F40006, 12F40005, 12F40019, 12F37016, 12F37005, 12F37043, 12F39006, 12F39005, 12F39019, 12F38005, 12F38007, 12F37007, 12F39007, 12F40007, 12F38014, 12F37014, 12F39014, 12F40014 e 12F38009) and three witnesses: BRS 610, BRS 655 and Volumax. It estimated productivity per area, in vitro dry matter digestibility, and assessed the bromatological and fermentation characteristics of sorghum silage. In vitro dry matter digestibility, unavailable protein in neutral detergent, neutral detergent fiber corrected for ashes and protein, acid detergent fiber, hemicellulose and lignin differed as to the genotypes tested. The pH and the ammoniacal nitrogen of the silage also showed differences between genotypes. Most of the genotypes tested are favorable for silage production, except the hybrid with higher lignin content 12F370014, and the hybrids 12F37007 and 12F370014, which showed the highest NDFap values.