PSIII-6 - Relationship of geographical location, cattle type, sex, and pen size to rates of liver abnormalities

Bovine liver abscess outcomes of individual animals (n = 989,296) were observed from 2013 to 2021 on a pen (n = 6,420) basis to quantify liver abscess prevalence and severity, as well as other liver abnormalities such as liver flukes. Cattle originated from 122 feedlots located in Arizona, Colorado, Idaho, Kansas, Minnesota, Missouri, Nebraska, Oklahoma, and Texas. Livers were audited at eighteen different beef abattoirs. Observational categories included sex (heifer, steer), cattle type (Holstein, beef-type), and pen count. Pen counts were grouped ( < 40, 41-80, 81-160, 161-320, and >320) to quantify the association of pen size on liver abscess outcomes. Data were analyzed as a series of binomial proportions using generalized linear mixed models with fixed effects of observational categories (cattle type, feedyard location, pen size and sex). Cattle fed in Oklahoma or Texas exhibited greater (P < 0.01) frequency of liver flukes (3.2% vs 0.5%) than cattle fed in Colorado or Nebraska. Cattle fed in Colorado, Kansas, Missouri, Nebraska, Arizona, and Oklahoma exhibited fewer (P < 0.01) total abscesses (23.5%, 26.0%, 23.6%, 19.3%, 16.9%, and 18.1%) than cattle fed in Idaho, Minnesota, and Texas (36.4%, 36.4%, and 33.2%). Beef-type cattle were observed to exhibit fewer (P < 0.01) total abscesses (22.0% vs 41.1%) and fewer (P < 0.01) severe abscesses (10.2% vs 26.4%) than Holstein cattle. Likewise, native heifers exhibited fewer (P < 0.01) total abscesses (20.6% vs 23.3%) and fewer (P < 0.01) severe abscesses (9.3% vs 11.1%) than native steers. Abscess prevalence differed as a function of pen size. Both total abscess and severe abscess rates decreased (P < 0.01) as animal count within a pen increased (32.66%, 27.47%, 27.86%, 23.17%, and 20.33%; 17.20%, 14.48%, 14.80%, 11.45%, and 9.14%). These results suggest liver abscess prevalence and severity is effected by a wide range of factors.