Longitudinal assessment of Fusobacterium necrophorum and Fusobacterium varium in the nasal cavity of finishing beef steers with and without liver abscesses

Objective

We longitudinally assessed the prevalence of Fusobacterium necrophorum ssp. necrophorum, Fusobacterium necrophorum ssp. funduliforme, and Fusobacterium varium in the nasal cavity of finishing beef steers with and without liver abscesses (LA).

Materials and Methods

Crossbred beef steers (n = 225; arrival BW = 353 ± 39.6 kg) were transported to a feedlot and used in a case-control study. From d 0 to harvest, steers were fed a feedlot diet representative of the High Plains region (NE_g = 1.50 Mcal/kg). Nasal swabs were aseptically collected after feedlot arrival (d 5), after adaptation to the finishing diet (d 35), and the day before harvest (harvest). Livers were collected at harvest and examined for LA, and cattle were subsequently assigned into either case (LA present) or control (LA not present) groups. Nasal swabs from cattle with LA (n = 42) and without LA (n = 42) were analyzed for Fusobacterium. Individual animal was the experimental unit, with fixed effects of abscess, sampling time, and abscess × sampling time interaction.

Results and Discussion

Overall LA prevalence was 18.7%. Nasal prevalence of F. necrophorum ssp. necrophorum and F. varium did not differ by LA status or sampling period. Conversely, an abscess × sampling interaction occurred, where steers with LA had lesser F. necrophorum ssp. funduliforme prevalence on d 35 than those without a LA. Nevertheless, the number of enumerable F. necrophorum ssp. funduliforme samples did not differ between steers with or without LA or across sampling time.

Implications and Applications

This is the first report of Fusobacterium detection and enumeration from the nasal cavity of feedlot beef steers. Although these data suggest that Fusobacterium species are present in the nasal cavity of finishing beef steers throughout the feedlot period, a direct link between nasal Fusobacterium populations and LA development was not detected. High variability and small sample sizes limited our ability to detect subtle associations. Future research is needed to evaluate relationships between Fusobacterium populations in the respiratory tract, respiratory disease prevalence, and LA formation.