Longitudinal assessment of the prevalence of Fusobacterium necrophorum, Fusobacterium varium, and Salmonella enterica in the nasal cavity, ruminal fluid, and feces of finishing beef steers with and without liver abscesses

The objective was to longitudinally assess the prevalence of <i>F. necrophorum</i> subsp. <i>necrophorum</i>, <i>F. necrophorum</i> subsp. <i>funduliforme</i>, <i>F.</i> var<i>ium</i>, and <i>Salmonella enterica</i> in the nasal cavity, ruminal fluid, and feces of finishing beef steers with and without LA. Crossbred steers (<i>n</i> = 225; 353 ± 39.6 kg) were transported to a feedlot and fed a high-concentrate diet. Nasal, ruminal fluid, and fecal samples were collected following feedlot arrival (d 5), 1 week after adaptation to a finishing diet (d 35), and the day before harvest (study end). Livers were collected at harvest and examined for LA, and cattle were subsequently assigned into either control or liver abscess groups. Overall LA prevalence was 18.7%. The concentration and prevalence of <i>Salmonella</i> decreased in ruminal fluid and increased in feces with days on feed (<i>p</i> < 0.01). Conversely, ruminal fluid prevalence of <i>F. necrophorum</i> subsp. <i>necrophorum</i> and <i>F.</i> var<i>ium</i> increased with days on feed (<i>p</i> < 0.01). <i>Fusobacterium</i> abundance in ruminal fluid and feces was not indicative of LA development except for <i>F. varium</i> being more abundant in the ruminal fluid of steers with LA (<i>p</i> < 0.01). Abundance of <i>F. necrophorum</i> subsp. <i>necrophorum</i> was greater in abscessed liver tissue than healthy tissue (<i>p</i> = 0.03), although no other differences in bacterial abundance or prevalence were observed in livers. Overall, <i>Fusobacterium</i> and <i>Salmonella</i> prevalence in the nasal cavity, ruminal fluid, and feces were affected by days on feed, but their prevalence and abundance were not indicative of LA occurrence.