Experimental site and treatment
The present study was carried out in the Animal Nutrition
Laboratory of the Faculty of Zootechnology and Ecology
of the Autonomous University of Chihuahua, Mexico. The
in vitro gas production technique (IVGPT) (Theodorou et al.
1994) was used to compare the effect of the addition of
two yeast strains of Candida genre to an in vitro ruminal
fermentation of two fibrous substrates. In order to achieve
that, two experiments were carried out with oat straw as
substrate (A. sativa) and alfalfa hay as substrate (M. sativa).
Both experiments compared yeast strains isolated
from the rumen of Holstein cows. The Levica 25 strain,
belonging to C. tropicalis species, located in GenBank with
number JF894145, which belongs to the collection of yeast
ICA (RYCASI) with registration number 980 at the World
Data Centre for Microorganisms (WDCM). The Levazoot
15 strain, belonging to C. norvegensis species, located in
GenBank with number JQ519367.1, which belongs to the
Faculty of Zootechnology and Ecology of the Autonomous
University of Chihuahua (UACH), Mexico. Previous studies
demonstrated that both yeast cultures modified substantially
in vitro ruminal fermentation patterns (Marrero et al. 2013;
Castillo 2009).