203 Ruminal papillae characterization and ruminal metabolomics of beef on dairy heifers with abscessed or non-abscessed livers.

Abstract Ruminal papillae histology and ruminal volatile fatty acid (VFA) profile of feedlot heifers with abscessed and non-abscessed livers were evaluated. A randomized complete block (kill group) design was used to source heifers (beef-on-dairy) finished in a steam-flake corn-based diet, upon harvest, in which 94 and 110 ruminal tissue and fluid collections were performed from animals with and without liver abscesses, respectively. Selection of animals were determined in pairs, as abscesses were identified at the viscera inspection line. A 1-cm2 individual fragments from the ventral cranial-sac of the rumen were collected for the histological assessment, while ruminal fluid was taken and immediately frozen (dry ice). The histological laminas were prepared (embedded in paraffin wax, sectioned at 4 µm and stained with hematoxylin and eosin) for microscopic cellular assessment. Ruminal fluid was processed and analyzed for VFA using gas chromatography. The GLIMMIX procedure of SAS was used for statistical analysis utilizing animal as the experimental unit, the fixed effect of liver abscess presence, size (small or large) intensity (local or diffuse), location (left, right, both), or diffusion (local or diffuse), while lot within harvest-group was used as random effect. The papillae histology identified (P ≤ 0.02) that animals with liver abscess had papillae with greater height, area, and thinner keratin layer while there was no difference between width (P = 0.88). Animals with liver score (A+) showed a thinner papillae keratin layer (P = 0.05), while those with large abscesses show greater heigh (P = 0.04) and thinner keratin layer (P = 0.04). Animals with diffused abscesses across the liver had papillae that were taller (P = 0.06), with greater area (P = 0.05), and thinner keratin layer (P = 0.04) compared to those with non-abscessed liver. Abscess lobe location (P ≥ 0.11) and papillae cellular mitotic index were not affected (P ≥ 0.64) by any variable in current assessment. Ruminal VFA profile, total, and C2:C3 molar proportions (collected upon harvest time) were not affected by the presence of liver abscess (P ≥ 0.19). Ruminal papillae histologic microscopic measurements revealed that animals with liver abscess (influenced by presence, size, and diffusion) had more pronounced and vulnerable ruminal papillae tissue.