Figure 3.

(a) Ratio of ¹³C-enrichment in milk and serum retinol, determined by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS), of lactating sows (n = 6) after a 20 μmol dose of ¹³C₂-retinyl acetate. At%, atom percent of ¹³C in total carbon. (b) Milk concentration at each sampling timepoint following dosing. Error bars represent SD. (c) Estimated cumulative percent of the ¹³C₂-retinol dose lost through the milk of lactating sows, determined by GC-C-IRMS, which was calculated as the area under the curve, determined by trapezoidal approximation, of the product of the retinol concentration and tracer-tracee ratio of ¹³C₂ enrichment of milk retinol over time, multiplied by average milk production of a sow [10 L/d]²⁰.