PSVII-40 - Late-Breaking Abstract: Ultrasonography and bacterial community of naturally occurring liver abscesses and non-abscessed livers in finishing Holstein steers
Wednesday, July 22, 2020
7:00 AM – 5:00 PM
Location: Poster Sessions
Liver abscesses persist in feedlot cattle representing a financial burden to both pre- and post-mortem sectors of the beef industry. Pre- and Post-mortem strategies are needed to understand onset, duration, and resolution of abscesses, etiology, and fully quantify their impact on performance. Holstein steers (n = 56; Initial BW=384±13.5 kg) consuming a finishing diet (90% concentrate) for 188 d (Final BW=660±42 kg) were used for live ultrasonography of the liver. Feed intake was recorded daily and BW and liver ultrasound images recorded every 28 d. At harvest, livers were graded and imaged to compare with ultrasound images. Tissue was sampled from both abscessed and non-abscessed livers and 16s rDNA sequencing performed. Steers ranked within feedlot performance variables for 188 days on feed (DOF) and the final 48 DOF were compared with post-mortem liver score using the FREQ procedure of SAS. A contingency table for abscess detection by ultrasound versus harvest was used to evaluate ultrasound accuracy. Abscess prevalence of Holstein steers was 60.7%. No relationship was detected between liver severity score and DMI, ADG and G:F calculated from the total days on feed (P ≥ 0.394). However, in the last 48 DOF, steers with non-abscessed or resolved liver abscesses tended to have greater ADG values (P = 0.099) and G:F (P = 0.049) than steers with mild and severely abscessed livers. Final ultrasound identified 14 of 23 abscessed livers. Abscesses not detected by ultrasound were inactive scars/adhesions, located on the visceral side or covered by lung or intestinal tissue. Non-abscessed and scarred livers had greater OTU richness and evenness while severely abscessed livers had greater dominance (P < 0.001). Beta-diversity indicated community separation of tissue from different severity scores. All 56 liver samples contained F. necrophorum and Bacteroides spp. DNA; abscessed or not. The true prevalence and duration of liver abscesses in finishing cattle requires greater pre-mortem surveillance.