Participation of the reticulorumen and omasum in the total absorptive surface of the bovine forestomach

Abstract

About 50% of volatile fatty acids (VFA) produced in the reticulorumen are absorbed in this compartment. The other 50% pass with the fluid phase to the omasum and are absorbed before the duodenum. The objective of this experiment was to measure the absorption surface of the reticulorumen and omasum aiming to compare it with the absorption magnitude. Eight adult bovines had their stomachs removed immediately after slaughtering. The stomach compartments were separated and weighed. Fragments were collected from several anatomical regions. Measurements of the total area of the internal surface were taken through image capture and analysis. The reticulorumen absorptive surface (7.7 m²) was larger (P<0.001) than the omasum absorptive surface (2.1 m²). The surface/digest ratio, however, was larger (P=0.07) in the omasum (0.22 m²/kg) than in the reticulorumen (0.12m²/kg), representing an omasum surface area for each digest unit 83.3% larger. The area of one of the rumen ventral sac fragments showed a positive correlation (0.84) with the total rumen surface area, indicating that it is possible to estimate the total rumen area by biopsy. The absorptive surface of the forestomach compartments seem to be compatible with absorption magnitude. However, further studies comparing VFA fractional absorption rate among forestomach compartments should be carried out.