Effect of forage to concentrate ratio and monensin supplementation on cis-9, trans-11 conjugated linoleic acid and trans-11 octadecenoic acid concentrations of ruminal contents and plasma in sheep

Abstract

Twenty-four cannulated Small-tailed Han×Poll Dorset wethers (BW 47.5±2.1 kg) were used to determine the effects of forage to concentrate ratio (40:60 vs. 70:30), monensin supplementation (0, 15 or 30 ppm, DM basis) and interactions of these two factors on cis-9, trans-11 conjugated linoleic acid (cis-9, trans-11 CLA) and trans-11 octadecenoic acid (trans11-C 18:1) concentrations in ruminal contents and plasma in sheep. The experiment was designed as a 2×3 factorial. The diet contained Chinese wild rye grass hay (Aneurolepidium Chinese), cracked corn, soybean meal, NaCl, limestone and trace mineral premix. Dietary crude fat and linoleic acid (C 18:2n-6) were adjusted with soybean oil to about 7.0% and 24.0 mg/g (DM basis), respectively. High forage diets increased (p<0.001) the concentrations of trans11-C18:1 and cis-9, trans-11 CLA in ruminal contents and plasma. Monensin supplementation increased (p<0.001) the concentration of trans11-C18:1 in ruminal contents, but had no effect on that of cis-9, trans-11 CLA. Concentrations of trans11-C18:1 (p<0.019) and cis-9, trans-11 CLA (p<0.022) in plasma increased with dietary monensin levels. Interactions of forage: concentrate ratio and monensin level tended to affect the concentrations of trans11-C18:1 (p<0.091) and C18:2n-6 (p<0.083) in ruminal contents. Increasing forage levels increased the concentrations of trans11-C 18:1 and cis-9, trans-11 CLA in the rumen. Supplementing with monensin increased the ruminal production of trans11-C18:1 and concentrations of trans11-C18:1 and cis-9, trans-11 CLA in plasma.