Identification and characterization of yeasts from bovine rumen for potential use as probiotics.

The aim was to isolate, identify and characterize yeasts present in rumen fluid and to select strains showing potential as probiotics. Rumen fluid was sampled from 4 herds of dairy and beef cattle and 77 yeast isolates were identified. Initial screening was based on the capacity to maintain viability in a medium with different ruminal conditions. A second screening in fresh rumen fluid to assess the growth of inoculated yeasts and evaluate in vitro neutral detergent fibre digestibility (NDF-D), pH and acid accumulation was conducted. The yeast population ranged from 3·84 to 6·76 log10 CFU per ml. The main species of yeast found were Pichia kudriavzevii, Candida rugosa, C. pararugosa, C. ethanolica and Magnusiomyces capitatus. Strains CCMA 933 (C. rugosa) and CCMA 970 (C. pararugosa) showed greater ability to survive in ruminal fluid and stimulated the production of acids. Isolate CCMA 967 (C. ethanolica) survived and improved the NDF-D. Pichia kudriavzevii was the dominant yeast found in the cattle herds. Strains CCMA 933, CCMA 970 and CCMA 967 showed properties that could be useful as potential probiotics for cattle. This study was the first to select yeasts from the rumen fluid, with the potential to be used as probiotic, based on the ruminal conditions.