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Identification and characterization of yeasts from tropical silages and evaluation of their effects on rumen fermentation and animal performance


When silages with a high number of yeasts are fed to animals, these microorganisms are ingested in large amounts and may be present in high concentrations in the rumen fluid. The objectives of this work will be: 1) identify the species of yeast present in silages cultivated in tropical regions; 2) characterize these microorganisms in relation to the utilization of substrates for growth; 3) determine the effect of the most predominant yeasts on silage fermentation and evaluate the utilization of silage additives to control these microorganisms; 4) evaluate the effects of yeasts on ruminal fermentation and animal performance. The first phase of the project will be dedicated to the identification and characterization of yeast present in silages. The species will be identified by sequencing the internal transcribed spacer region of ribosomal DNA. Each species will be characterized by the substrate utilization profile through the use of commercial methods for identification of yeasts. In the second phase, the most predominant species will be grown in liquid media and it will be added to the fresh forage at the time of ensiling for evaluation of silage fermentation profile and microbial population. In the last phase, pure culture of yeasts will be inoculated in silages and in the total mixed rations and fed to fistulated animals and to lactating dairy cows for evaluation of ruminal fermentation parameters, dry matter intake, animal performance, milk composition and fatty acid profile of milk fat. Upon completion of this study, it will be possible to determine the species of yeast that are present in silage cultivated in tropical conditions, to understand the role of the most predominant yeasts on silage spoilage and to understand the effects of these microorganisms on ruminal fermentation parameters and animal performance. (AU)

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