Faecalibacterium Prausnitzii: Isolation, Characterization And Effects On Dairy Calves

Abstract

FAECALIBACTERIUM PRAUSNITZII: ISOLATION, CHARACTERIZATION AND EFFECTS ON DAIRY CALVES Replacement heifers are extremely important for the success of a dairy farm. Strategies to improve performance while maintaining welfare, health and expenses at optimal levels are the focus of many research groups. Results from a previous study showed that young calves with a higher relative abundance of Faecalibacterium prausnitzii had a better weight gain and decreased incidence of diarrhea during the preweaning period. Our hypothesis was that the administration of F. prausnitzii could improve gastrointestinal health and performance of preweaned heifers. The first objective of this thesis was to advance our knowledge on the anaerobic bacterium F. prausnitzii and its in vitro characteristics. The second objective was to test its effects in vivo, administering it to newborn calves. In order to achieve our first objective, 203 isolates of F. prausnitzii were isolated from the feces of calves and piglets. Forty genetically distinct F. prausnitzii isolates were selected for further characterization. A large variability was observed among isolates for in vitro short chain fatty acid metabolism, growth, antibiotic resistance, and sensitivity to low pH and bile salts. Based on this data, 4 isolates with desirable characteristics were selected and used as part of a probiotic cocktail in the subsequent in vivo studies. To accomplish our second objective two trials were completed. First a safety trial was conducted using 30 newborn bull calves. Since no adverse effects of the oral and rectal administration of F. prausnitzii to neonatal calves were observed, a large field trial was performed in a commercial farm. This last study demonstrated that the oral administration of F. prausnitzii reduced the incidence of severe diarrhea and related mortality rate and increased weight gain in preweaned dairy heifers. The results presented in this thesis contribute to the knowledge about F. prausnitzii characteristics. Moreover, our studies demonstrated that F. prausnitzii administration to newborn calves is safe and proved the concept that this commensal bacterium is a promising probiotic for newborn calves. Further research is needed to evaluate in vivo mechanisms of action and interactions between this microbe, the gut microbiota and the host