Effects of the ionophore salinomycin on nitrogen and long-chain fatty acid profiles of digesta in the rumen and the duodenum of sheep

Abstract

Modes of salinomycin action on digestion with special regard to nitrogen and long-chain fatty acid utilization were investigated in sheep equipped with ruminal and duodenal cannulae. Sheep were fed hay (300 g day −1 as fed basis) and concentrate (500 g day −1 as fed basis) with or without 32 ppm salinomycin. Digesta flow was monitored with a dual marker administration method. Dietary nitrogen flow at the duodenum was higher in salinomycin-fed sheep than in control sheep (8.0 g day −1 vs. 6.2 g day −1, P < 0.05) when the estimation was based on purine bases as a bacterial marker. Slight depression in bacterial growth with salinomycin feeding was observed, even though it was not significant. Sheep on a diet with salinomycin tended to retain more nitrogen, although this was non-significant. Duodenal digesta in sheep fed salinomycin was richer in unsaturated fatty acids, in particular oleic acid, than those in control sheep (23.6% vs. 9.1%, P < 0.01). Ruminal digesta and rumen bacterial samples showed the same trend with duodenal digesta. These results suggest that salinomycin would inhibit ruminal biohydrogenation of unsaturated fatty acids.