Absorption and metabolism of volatile fatty acids by rumen and omasum

João Luiz Pratti Daniel,João Chrysostomo de Resende Júnior

doi:10.1590/s1413-70542012000100012

João Luiz Pratti Daniel, João Chrysostomo de Resende Júnior

Open Access

https://doi.org/10.1590/s1413-70542012000100012

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Abstract

Volatile fatty acids (VFA) absorption and metabolic capacity of rumen and omasum were compared, in vitro. Fragments of rumen wall and omasum laminae were taken from eight adult crossbred bovines. An isolated fragment of the mucosa was fitted in a tissue diffusion chamber. Valeric acid and CrEDTA were added to ruminal fluid and placed on the mucosal side and buffer solution was placed on the serosal side. Fractional absorption rates were measured by exponential VFA:Cr ratio decay over time. Metabolism rate was determined as the difference between VFA absorbed and VFA which appeared on the serosal side over time. Mitotic index was higher in omasum (0.52%) than in rumen epithelium (0.28%). VFA fractional absorption rate was higher in omasum (4.6%/h.cm²) than in rumen (0.4%/h.cm²). Acetate, propionate, butyrate, and valerate showed similar fractional absorption rates in both fragments. Percentage of metabolized acetate and propionate was lower than butyrate and valerate in both stomach compartments. In the rumen, individual VFA metabolism rates were similar (mean of 7.7 , but in the omasum, valerate (90.0 was more metabolized than butyrate (59.6 propionate (69.8 and acetate (51.7 . Correlation between VFA metabolism and mitotic index was positive in the rumen and in the omasum. In conclusion, VFA metabolism and absorption potential per surface of the omasum is higher than that of the rumen. Variations on rumen and omasum absorption capacities occur in the same way, and there are indications that factors capable of stimulating rumen wall proliferation are similarly capable of stimulating omasum walls.

Highlights

Absorptive surfaces of reticulorumen (DIRKSEN et al 1984) and probably that of omasum (BALDWIN et al 2004) are directly related to Volatile fatty acids (VFA) absorption capacity
Animals were slaughtered by exsanguinations after stunning, and the forestomach was removed from abdominal cavity 5 to 10 minutes later
Higher surface:digesta mass ratio in omasum (DANIEL et al 2006) could maximize VFA local stimulation on cell proliferation, since large amounts of VFA pass from reticulorumen to omasum incorporated to the ruminal fluid phase (RESENDE JÚNIOR et al 2006)

Summary

Introduction

Absorptive surfaces of reticulorumen (DIRKSEN et al 1984) and probably that of omasum (BALDWIN et al 2004) are directly related to VFA absorption capacity. The understanding of omasal physiology seems to be as important in the control of current digestive disturbances as the understanding of ruminal physiology. Despite the absorptive surface of reticulorumen (7.7 m2) being higher than that of the omasum (2.1 m2) (DANIEL et al 2006), and absorption and metabolism potential of the rumen being well documented, the potential of absorption and metabolism of the omasum and any comparison of these parameters among organs are poorly understood. The purpose of this work was to compare, in vitro, VFA absorption and the metabolism capacityof rumen and omasum.

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