Investigation of Precursors of Ruminal Fatty Acids of Sheep Fed Purified Diets

Abstract

The in vivo and in vitro incorporation of C¹⁴-labeled bicarbonate and acetate-2-C¹⁴ into the ruminal volatile fatty acids of sheep receiving purified diets was studied. In the bicarbonate-CO₂ studies, most of the incorporated label was found in propionate and the specific activity of valerate exceeded that of either acetate or butyrate in all cases. A difference in incorporation rates between the sheep receiving diet 1 (Na plus K) and the sheep fed diet 1 was suggested and the addition of sodium and potassium bicarbonates to the diet enhanced C¹⁴O₂ incorporation into the fatty acids in the in vitro studies. A product-precursor type relationship between acetate and butyrate was encountered in the in vivo experiments and this relationship received additional support from the fatty acid analyses. Here again, the presence of the supplementary sodiumand potassium bicarbonates enhanced the incorporation of C¹⁴. Volatile fatty acid analyses revealed relatively higher levels of propionate in the rumen fluid of the sheep receiving diet 1 (Na plus K) than observed in rumen fluid from the sheep fed diet 1.