Splanchnic metabolism of volatile fatty acids in the dairy cow

Summary

This review challenges the long-held assumption that the ruminal epithelium metabolises a large proportion of volatile fatty acids during their absorption. New evidence indicates that the ruminal epithelium metabolises negligible amounts of acetate and propionate, but has substantial fractional uptake of butyrate and valerate. The liver takes up 0.9 or more of absorbed propionate, though multiple regulatory factors influence hepatic metabolism and propionate availability does not directly determine glucose supply. The author emphasises the need for future research to integrate understanding of rumen digestion with nutrient availability to productive tissues.

Regional applicability

The findings are directly applicable to United Kingdom dairy farming, as the metabolic physiology of volatile fatty acid utilisation is universal across dairy cattle populations. Understanding VFA metabolism is fundamental to optimising feeding strategies and milk production efficiency in UK dairy systems.

Key measures

Fractional uptake and metabolism of acetate, propionate, butyrate, and valerate by ruminal epithelium and liver; hepatic propionate uptake; glucose availability to dairy cows

Outcomes reported

The study examined the metabolic fate of volatile fatty acids (acetate, propionate, butyrate, and valerate) as they are absorbed from the rumen and processed by splanchnic tissues (ruminal epithelium and liver) in dairy cows. Key findings challenged the prevailing assumption that the ruminal epithelium metabolises a large fraction of VFA during absorption.

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