João Paulo Sampaio Rigueira

The chemical composition, fermentation profile, and microbial populations in tropical grass silages

The objective of this study was to evaluate the fermentation profile, chemical composition and microbial population and losses in the silages of signalgrass and Mombasa grass fertilized with the following levels of nitrogen (N): 0, 30, 60 and 90 kg/ha. The grasses were harvested at 70 days of regrowth, chopped and then ensiled in laboratory silos that had 20 kg of capacity and a snap-top cover and were fitted with Bunsen valves. Before ensiling, samples of the plants were used for the isolation and identification of lactic acid bacteria (LAB) in epiphytic microbiota. The design adopted was a 4 × 2 factorial arrangement, with four doses of N and two forage species, in a completely randomized design, with four replicates. The predominant species of LAB was Lactobacillus fermentum. The interaction between the N dose and forage species affected the dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and water soluble carbohydrates (WSC) of the silages. The pH values and gas losses were influenced only by the forage species, with higher values for the Mombasa grass. For the ammonia (NH3-N) levels and effluent losses, there was an effect of the interaction between the forage species and N doses, and the highest values of NH3-N and effluent losses were found in the Mombasa grass silage fertilized with 60 kg N/ha. Nitrogen fertilization reduces the levels of DM and WSC in the silages and also increases the levels of CP, NH3-N and effluent losses.

Nutritional value of sorghum silages

This study aimed to evaluate the nutritional characteristics and quality of silages of five sorghum genotypes, namely: Volumax, AG2005E, Qualimax, BRS610 and AG2501. The study was conducted at the Experimental Farm Unimontes, in the municipality of Janauba, state of Minas Gerais. The treatments were distributed in a randomized block design with four replicates. Data were tested by analysis of variance andmeans were compared by Scott-Knott test at a significance level of 5%. The pH values ranged from 3.93 and 4.10. Genotypes differed in all studied nutritional characteristics (p < 0.05). For the acid detergent fiber, differences were detected between the genotypes, AG2501 (35.66%), Volumax (34.89%), AG2005E (34.53%), Qualimax (32.39%) and BRS610 (33.60%). The high participation of lignin was verifiedin all genotypes except for Volumax (4.14%). All silages were within the recommended range 50-65% for in vitro dry matter digestibility and classified as having good quality, however only the AG2005E genotype met nitrogen requirements for microbial fermentation, with 7.06% crude protein.

Produtividade e composição bromatológica de Brachiaria spp., no Alto Vale do Jequitinhonha

Avaliaram-se a produtividade de materia seca (MS), proporcao de lâminas e composicao bromatologica de Brachiaria spp., colhidas com 42 dias de rebrotacao, em Diamantina, MG. Para a determinacao dos teores de MS, PB, FDN, FDA e lignina utilizaram-se o esquema em parcelas subsubdivididas, no DIC, com quatro repeticoes. Nas parcelas foram distribuidas as cultivares Basilisk, Marandu, Xaraes, Llanero e B. humidicola comum; nas subparcelas, dois cortes, e, nas subsubparcelas, dois anos experimentais. A producao de MS total e a proporcao de lâminas foram analisadas em esquema de parcelas subdivididas, com especies/cultivares nas parcelas e anos nas subparcelas. A producao de MS no segundo ano (3 cortes) foi mais alta que no primeiro (2 cortes), destacando-se as cultivares Basilisk, Xaraes e Llanero. De modo geral, as cultivares apresentaram teores satisfatorios de PB, mais altos no segundo ano. Os teores de FDN foram mais baixos no segundo ano e os de lignina mais baixos no primeiro ano. As cultivares Xaraes e Marandu destacam-se pela elevada proporcao de folhas e apresentam composicao bromatologica semelhante a da cultivar Basilisk. Associando-se a composicao bromatologica com a produtividade de MS, recomendam-se as cultivares Xaraes e Basilisk para as condicoes do Alto Vale do Jequitinhonha.