Isolation, identification and growth determination of lactic acid-utilizing yeasts from the ruminal fluid of dairy cattle

Ruminal organic acid production, especially lactic acid, can be modified by feeding cattle highly concentrated diets, which have been shown to adversely affect dairy cattle health. Therefore, the use of lactic acid-utilizing organisms is considered to be a potential method for controlling lactic acid levels. This study was conducted to isolate and identify lactic acid-utilizing yeasts from the ruminal fluid of dairy cattle and to determine the specific growth rate and generation time when using lactic acid as a carbon source instead of glucose. Seventeen yeast isolates were examined in this study. Yeasts isolated from dairy cattle that were fed a high cassava pulp diet (HCP) had higher specific growth rates and shorter generation times than yeasts isolated from dairy cattle that were fed a high-concentrate diet (HC) and a mixed diet (M). The three most effective yeasts in terms of specific growth rate and generation time were Pichia kudriavzevii, Candida rugosa and Kodamaea ohmeri, with 99, 100 and 99% nucleotide identities, respectively. These three isolates could be used as potential probiotics in dairy cattle diets.