Measurement of urinary and plasma estrone sulphate concentrations from pregnant sows

The accuracy of urinary estrone sulphate (E1S) concentrations as an indication of pregnancy was compared to that of plasma E1S concentration. Urine and plasma were collected from 145 sows 18 to 30 days after mating. Concentrations of E1S in urine were indexed to creatinine concentration (CR) and specific gravity (SG) to correct for urine dilution. There was no significant difference in E1S concentration between urine corrected for CR or SG and uncorrected urine (UN) from pregnant sows. Urinary E1S concentrations were 20 to 100 times higher than plasma E1S concentrations. The E1S test was accurate in the detection of pregnancy in sows using both plasma and urine (test sensitivity, 98.8% vs. 96.4%, respectively) during the optimal sampling period of 20 to 30 days post mating. The test was slightly more accurate (NS) using plasma than urine in detecting non-pregnant sows (test specificity, 100.0% vs. 91.9%, respectively) 20-30 days after mating. Urinary E1S concentrations could be used to predict litter size, but the precision was poor ( +/- 3 piglets), and thus could only be used to predict small (less than 5 piglets), medium (6-10 piglets) and large (greater than 11 piglets) litters.