WS Shifting the paradigm of liver abscess dogma in USA feedlots

Abstract Text: Liver abscesses in feedlot cattle are a major economic, welfare and production concern to the cattle feeding industry. Severe liver abscesses (LA) reduce ADG by as much as 0.20 kg, DMI by 5%, trimming loss by 0.43%, carcasses grading choice by 7%, and HCW by 36 kg. In processing facilities, LA introduce operational and food safety concerns. These include a reduction in processing efficiency, lost time as a result of line stoppages and offal condemnation in addition to the consumer risk associated with LA contamination of edible meat. Tylosin phosphate, a macrolide antibiotic, has been shown to reduce LA by 75% and level of Fusobacterium Necrophorum in the rumen by 80 to 90%. During this initial observational study, a total of 83 feedlot pens (each individual feed yard exceeding 40,000 head capacity) within three geographical regions (Arizona, Colorado and the Texas Panhandle) were sampled. Feedlot pen data were collected within 1 wk prior to harvest and cattle were traced to the packing plant. Every third rumen and its matching liver were tagged (if condemned only). Rumens were scored for consolidation, scars, moderate and acute lesions and a sample was taken. Livers were scored based on an adaptation of the Elanco Liver Check scoring system. Holstein cattle had a greater (P < 0.05) percentage of LA than beef breeds (30.3 vs. 20.0%). Additionally, Holstein cattle had 11% severe LA (A+) compared with 4% for beef breeds (P < 0.05). No geographical difference (P ≥ 0.10) were detected for liver abscess prevalence and averaged 23, 25 and 26% for The Texas Panhandle, Arizona and Colorado region respectively. Liver abscess rate and severe LA (A⁺) incidence differed between feedlots (P < 0.05) with within feedlot variation. A correlation was observed for LA% and days on feed (R² =0.22; P = 0.04) and for LA % and breed (R²= 0.29; P = 0.01). No correlation was observed between LA percentage and tylosin phosphate, and between LA percentage and rumen lesions (P ≥ 0.10). This data indicated no association between LA and rumen damage as a result of acidosis. Rumen lesions averaged 12.2%, of which 9.3% were consolidated, 2.4% scar tissue, and the remainder moderate and acute lesions. This study justifies further investigation of feedlot soil and manure as the source of LA causing pathogens to evaluate the within feedlot variation observed for in LA percentage in cattle.

Keywords: cattle, feedlot, liver abscess