REFERENCE : Alkan et al. Detection of twin pregnancies in ewes by pregnancy-associated glycoprotein assay and transabdominal ultrasonography. Domestic Animal Endocrinology 2020. https://doi.org/10.1016/j.domaniend.2019.106399

BACKGROUND

Fetal numbering is a complementary application of ultrasound to pregnancy assessment. It offers the opportunity to manage feeding and thereby reduce the prevalence of embryonic deaths, dystocia and toxemia. The transrectal route can be used (after an 8-hour fasting period) between the 25th and 40th day of gestation and the transabdominal route between the 45th and 100th day of gestation. The plasma concentration of PAG increases in the ewe between the 3rd and 4th week of gestation and until the 9th week, it remains constant thereafter.

MATERIAL AND METHODS

The authors of the study performed a transabdominal fetal count (5 MHz probe) in 179 ewes at 40, 45, 50, 55 and 60 days of gestation. Blood was collected after each examination for PAG determination (pregnancy if ≥ 0.3 ng/ml). The number and sex of fetuses was recorded after each lambing.

RESULTS

The total % of twin gestations was 34% (Kangal-Akkaraman breed), 55% were male and 45% were female.

The concentration of PAG was significantly higher in case of twinning from 40 (Sensitivity 91% and specificity 58%) to 50 (Sensitivity 81% and specificity 59%) days.  From 55 to 60 days, this difference is no longer significant. This difference could be attributed to the higher number of binucleated cells. PAG does not determine the sex of the fetus even though the weight and size of the placenta are higher in male than female fetuses.

Ultrasound determination of pregnancy is most accurate on day 60 of gestation.

Ultrasound also has the advantage of being more convenient.