Abstract

The objective of this study was to evaluate the aerobic microbiota of the rumen fluid from Holstein cows and heifers fed different tropical forage in the north of Minas Gerais, Brazil. A total of 30 samples of rumen fluid from cows fed with sorghum silage were collected: 32 from cows fed Brachiaria brizantha, 12 from heifers that received sorghum silage and 11 from calves fed sugar cane foliage. The culture was carried out using the agar Sabouraud medium and the solid C medium, containing microcrystalline cellulose. The isolated mycelial fungi were identified by microculture technique and yeasts by micromorphological and physical-chemical analysis. Specific identification for yeasts was confirmed by ribosomal DNA sequence analysis. The presence of fungal colonies was confirmed on the Sabouraud medium for 100% of the samples. No significant differences were observed comparing the concentrations of mycelia fungi in the rumen fluid from cows fed different forages and for the two categories evaluated, fed sorghum silage. Yeast populations in the rumen fluid from heifers fed sugarcane were higher compared with those receiving sorghum silage. The yeast Pichia kudriavzevii (Candida krusei) was the most frequent and among the mycelial fungi, the genus Aspergillus was the most frequently observed, corresponding to 56% of the samples. Future studies should elucidate the variations in the populations of these microorganisms considering the carbohydrate sources in the tropical forages and the animal categories. The ecological or pathogenic role of these microorganisms should also be considered, aiming at improved productivity and health of cattle.

Highlights

  • The rumen environment is characterized by a complex mixture of food fragments, water and microorganisms

  • The collection of rumen fluid samples was performed at the Fazenda Experimental do Instituto de Ciências Agrárias (ICA), owned by Universidade Federal de Minas Gerais (UFMG) and another farm located in the municipality of Montes Claros, which is located in the northern part of the state of Minas Gerais, Brazil

  • The positivity rate of fungi in the C medium for cows fed on pasture was significantly lower (86.7%) when compared with rates observed for cows fed sorghhum silage (100%)

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Summary

Introduction

The rumen environment is characterized by a complex mixture of food fragments, water and microorganisms At this site, there are populations of bacteria, ciliated protozoa, aerobic fungi, mycoplasma and bacteriophage, which establish various positive or negative interactions between themselves (Kamra, 2005; Lopes et al, 2002). There are populations of bacteria, ciliated protozoa, aerobic fungi, mycoplasma and bacteriophage, which establish various positive or negative interactions between themselves (Kamra, 2005; Lopes et al, 2002) Forages have their growth rate and maturity determined by factors such as water and soil nutrients, temperature and luminosity (Van Soest, 1994), directly influencing the diet quality and the levels of volatile fatty acids (VFA) and ammonia (NH3) available in the rumen. Fungi may sporadically cause infections in animals, humans and plants, and these lesions are frequently associated with predisposing factors (Casadevall, 2007)

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