The effect of handling methods on subsequent plasma progesterone levels in sheep

The mean progesterone concentration in the plasma of 10 adult Ethiopian Highland sheep obtained immediately after slaughter was 10.56 +/- 3.98 ng/ml. Samples were subsequently incubated at 4 degrees C, room temperature (19-22 degrees C) or 26 degrees C as either plasma or intact but citrated blood. Failure to separate plasma affected the progesterone content at 2-72 h at room temperature or 26 degrees C (p less than 0.01 - p less than 0.0001). Incubation temperature affected the plasma concentration at 18 h (p less than 0.05) and 24 h (p less than 0.001). Although progesterone values were generally higher in separated plasma, disparity with the values from plasma separated from incubated citrated blood was small (r = 0.76-0.98). Progesterone concentration declined haphazardly after collection but sometimes exceeded the initial readings. This kept the average concentration of progesterone in plasma separated immediately after collection fairly constant and within 15% of zero time samples during the first 48 h.