The effect of an intranasally delivered Lactobacillus spp. cocktail on the upper and lower respiratory microbiome of dairy calves challenged with Mannheimia haemolytica. Nasopharyngeal and tracheal wash samples from cattle

Twenty-four Holstein bull calves (1-to-3-week old) received either an intranasal BT cocktail containing six Lactobacillus strains (3 × 109 CFU per strain) 24 h or saline (control) prior to intranasal Mannheimia haemolytica challenge (3 × 108 CFU). The effect on the upper and lower respiratory microbiome was assessed using 16S rRNA gene sequencing of nasopharyngeal swabs and tracheal wash samples.