An In Vitro Study on the Role of Cellulases and Xylanases of <i>Bacillus subtilis</i> in Dairy Cattle Nutrition

Abstract

The administration of Bacilli to dairy cows exerts beneficial effects on dry matter intake, lactation performance, and milk composition, but the rationale behind their efficacy is still poorly understood. In this work, we sought to establish whether cellulases and xylanases, among the enzymes secreted by B. subtilis, are involved in the positive effect exerted by Bacilli on ruminal performance. We took advantage of two isogenic B. subtilis strains, only differing in the secretion levels of those two enzymes. A multi-factorial study was conducted in which eight feed ingredients were treated in vitro, using ruminal fluid from cannulated cows, with cultures of the two strains conveniently grown in a growth medium based on inexpensive waste. Feed degradability and gas production were assessed. Fiber degradability was 10% higher (p p B. subtilis cellulases and xylanases effectively contribute to improving forage quality, justifying the use of Bacilli as direct-fed microbials to increase animal productivity.

Keywords

• ruminal fermentation
• animal probiotics
• direct-fed microbials
• fiber degradability
• gas production