Comparison of the merits of measuring equine chorionic gonadotrophin (eCG) and blood and faecal concentrations of oestrone sulphate for determining the pregnancy status of miniature horses.

This research article examines and compares the efficiency of three different methods for determining the pregnancy status in miniature horses: measuring the blood concentrations of equine chorionic gonadotrophin (eCG), blood concentrations of oestrone sulphate (OS), or faecal OS concentrations.

Comparing eCG, Blood OS, and Faecal OS Measurements

• The study looked into the effectiveness of different measurements in identifying pregnancy in miniature horses, specifically the blood concentrations of equine chorionic gonadotrophin (eCG), the blood concentrations of oestrone sulphate (OS), or faecal OS concentrations.
• The horses, that were pregnant between 40 and 140 days, had serum eCG concentrations over 1 I.U. mL-1, with peak concentrations occurring between days 50 and 120. It was however noticed that eCG measurements sometimes gave a ‘false positive’ diagnosis for pregnancy.

Notable Ranges and Concentrations

• The research found that plasma OS concentrations varied from 0.1 to 3.6 ng mL-1 in non-pregnant mares. In contrast, all pregnant mares beyond 100 days post-mating had plasma OS concentrations over 30 ng mL-1.
• The Faecal OS concentrations also varied considerably. For non-pregnant mares, the range was from 4 to 89 ng g-1. When it comes to pregnant mares 150 days or more after mating, 97% of samples had OS concentrations over 85 ng g-1 and none had concentration below 67 ng g-1.

Recommendations and Considerations

• According to the results of the research, eCG measurement is suitable for determining pregnancy status in miniature mares from 40 to 100 days post-mating.
• However, if a mare is diagnosed as ‘pregnant’, she should also undergo a blood OS test 100 or more days after mating to rule out the chance of “false positive” diagnosis.
• For determining pregnancy status in miniature mares 100 or more days post-mating, the recommended method is measuring blood OS.
• Lastly, while the measurements of faecal OS offers a non-invasive alternative to blood OS testing after 150 days post-mating, the study cautions that the differentiation between ‘pregnant’ and ‘non-pregnant’ levels of OS is not as distinct in faecal measurements as it is in the blood.