Pichia kudriavzevii KKU20 and Saccharomyces cerevisiae Exhibit Comparable Performance in Rice Straw Ensiling for Feed Efficiency and Growth of Thai Native Beef Cattle.

Objective: Objective: The study aimed to assess the effect of two yeast strains, Pichia kudriavzevii KKU20 and Saccharomyces cerevisiae, on the ensiling process of rice straw (RS) and its impact on nutritional digestibility, ruminal fermentation, energy utilization, and growth performance of Thai native bulls.

Methods: Eight Thai native bulls were randomly assigned to two groups: One group was fed RS ensiled with Pichia kudriavzevii KKU20 (n = 4), and the other group was fed RS ensiled with Saccharomyces cerevisiae (n = 4). The experiment included an 18-day adaptation period followed by a 60-day feeding period. The bulls received a concentrate diet formulated to meet their protein requirements.

Results: No significant differences (p > 0.05) were observed between the groups in terms of daily concentrate intake, roughage intake, overall intake, average daily gain (ADG), and feed conversion ratio (FCR). Similarly, ruminal parameters showed no significant differences between the two yeast treatments, including ruminal pH, ammonia concentration, blood urea nitrogen levels, total volatile fatty acids (TVFAs), and protozoal populations. Energy efficiency and nitrogen efficiency were also unaffected by the yeast strain used (p > 0.05).

Conclusion: Although no significant differences were found, Pichia kudriavzevii KKU20, a rumen-derived yeast strain, demonstrated comparable potential to Saccharomyces cerevisiae, a widely used commercial yeast with known efficacy. This suggests that P. kudriavzevii KKU20 could be a promising alternative for ruminant nutrition.