Measurements of circulating progesterone and estrone sulfate concentrations as a diagnostic and prognostic tool in porcine pregnancy revisited

Abstract The main goal of this study was to examine the utility of measuring systemic concentrations of steroid hormones, namely progesterone (P4) and estrone sulfate (E1S), for monitoring the progression of porcine pregnancy and predicting sow fertility. There were three subsets of artificially inseminated (AI’d) sows used in the present experiments: i. animals sacrificed on gestational day 20 (gd20; n=16) or ii. gd50 (n=16; Experiment 1), and iii. animals maintained throughout pregnancy (n=24; Experiment 2). Blood samples (10 mL) were drawn from the orbital sinus and the endocrine data determined at different time points (around ovulation/artificial insemination (gd0=1st AI, gd1=2nd AI, and gd2) and maternal recognition of pregnancy (gd11) as well as on gd20 and gd50 (during two periods of increased embryonic/fetal mortality in swine) were examined for correlations with the numbers of healthy, arrested and reabsorbing embryos (Experiment 1) or with the number of live, stillborn and mummified piglets recorded at farrowing (Experiment 2). No correlations were recorded between circulating concentrations of both steroids and the numbers of healthy, arresting or reabsorbing conceptuses on gd20 or 50 (Experiment 1). The number of corpora lutea (CL) was directly related to the number of healthy embryos/conceptuses on gd20 and 50 (r=0.71, P=0.007 and r=0.76, P=0.0007, respectively) and the number of arresting embryos on gd20 (r=0.54, P=0.05), and negatively correlated with the number of reabsorbing embryos on gd20 (r=−0.53, P=0.05). In Experiment 2, circulating P4 concentrations on gd11 related directly to the number of live-born piglets (r=0.46, P