Urinary eCG patterns in the mare during pregnancy.

The study investigated the patterns of equine chorionic gonadotropin (eCG) in the urine of pregnant mares, revealing that eCG concentrations in both urine and plasma rise significantly on Day 40 of pregnancy, peak by Day 60, and decrease by Day 200. The study used a variety of tests, including radioimmunoassays and enzyme-linked immunospecific assays.

Study Design and Methodology

• The researchers collected blood and urine samples from 12 mares from Day 25 to Day 210 of their pregnancies.
• For comparison, the same types of samples were collected daily through two consecutive ovulatory periods from five nonpregnant mares.
• The team utilized two methods, radioimmunoassays (RIA) and a commercial dipstick enzyme-linked immunospecific assay (ELISA), to detect eCG in both the urine and plasma samples.

Findings and Observations

• In the pregnant mares, eCG concentrations in the plasma and urine as detected by RIA significantly rose on Day 40, peaked by Day 60, and then slowly dropped to low levels by Day 200.
• ELISA seemed more reliable for detecting eCG in the plasma than in the urine. However, on peak days (Days 50 to 60), both the plasma and urine tested positive for eCG in all five pregnant mares.
• Between Days 65 and 85, the highest rate of positive eCG detections by ELISA was observed, involving 86% of the mares. The RIA detected the highest eCG concentration in the urine between Days 55 and 90.
• ECG-like immunoactivity was not detected by ELISA in the urine of cyclic (non-pregnant) mares. Moreover, the RIA showed variable patterns with increases in immunoactivity, but these could not be correlated with physiological events or cycles.

Conclusions and Implications

• This research found that the eCG in mare urine follows a similar profile as the eCG in plasma during their first trimester of pregnancy.
• The usage and effectiveness of the RIA and ELISA tests were revealed, identifying ELISA as effective for plasma testing and RIA for urine. This can potentially aid future equine pregnancy testing and monitoring methodologies.