Influence of ration on morphology, histology, and trace mineral content of sheep rumen papillae.

Abstract The sequential changes in rumen epithelial development and micromineral content were studied in 15 wethers initially fed a ground control ration (GC). Four sheep were killed, five were changed to a low energy ration (LE), and six were changed to a pelleted feed known to induce ruminal parakeratosis (RP). The LE and RP sheep were sacrificed at intervals. Rumen epithelium from three areas was analyzed for trace minerals. Sections from the ventral rumen were studied histologically. The rations and rumen fluid at slaughter were analyzed for trace minerals. Rumen fluid was analyzed for volatile fatty acids. The GC sheep had irregularly shaped papillae, with extremely hyperplastic epithelium and multilayered, vesiculated stratum corneum. The LF sheep papillae revealed rapid loss in color, size, iron content, and numbers, denuding large rumen areas. Keratinization and hyperplasia were reduced 50% from GC by 8 and 32 days, respectively. The papillae of the RP sheep showed typical parakeratosis by 35 days; papillae cellular hyperplasia was reduced by half in 35 days and keratinization increased 50% in 24 days. An epithelial copper to molybdenum ratio of 11:1 was found. Epithelial trace minerals varied with the rumen area and the ration.