Evaluation of a bovine visual pregnancy test for the detection of pregnancy‐associated glycoproteins in sheep

Abstract

Contents As sheep produce similar pregnancy‐associated glycoproteins (PAGs) to cattle, a commercially available bovine visual pregnancy test based on the detection of PAGs (visual‐PAG‐test) was evaluated in sheep. The test was performed with whole blood (WhB), plasma (P) and serum (S) of 163 pregnant and 153 non‐pregnant ewes. Additionally, 11 pregnant ewes were tested weekly from day 14 to 49 of gestation and monthly from day 60 to day 149. Ten ewes were sampled weekly from the date of lambing until day 63 post‐partum (p.p.). The sensitivity in mid‐pregnancy (n = 163) was 98.16% (WhB), 99.39% (P) and 99.39% (S) compared to transabdominal ultrasonography as the gold standard while the specificity (n = 153) was 94.12% (WhB), 76.47% (P) and 93.46% (S), respectively. During early pregnancy, all 11 ewes were correctly identified as pregnant on day 42 (100%); however, the test sensitivity decreased to 54.6% (WhB) and 63.6% (S and P, respectively) at day 49. The ewes were again consistently identified as pregnant on day 63 (P) or on day 119 (S, WhB). The test was consistently negative from day 42 p.p. onwards in eight out of ten ewes. Two ewes remained consistently positive until the last sample on day 63 p.p. In conclusion, the test could be used to accurately select pregnant ewes at day 42 with a drop in sensitivity at day 49. The sensitivity of the visual‐PAG‐test was good in mid to late pregnancy, and early detection of pregnancy was possible in individual animals. In some ewes, the PAGs were however detectable for more than 63 days p.p.—the previous breeding history should therefore always be taken into account for correct interpretation of the test results.

İvesi Koyunlarında Gebeliğin Erken Teşhisi İçin Sığır Hızlı Görsel PAG ELISA Testi ve Transabdominal Ultrasonografinin Değerlendirilmesi

“…In agreement with this report, the accuracy of transabdominal ultrasonography was determined to be 96% in the present study. The sensitivity determined for rapid visual PAG ELISA (97.6%) in the present study was in agreement with sensitivities previously reported in Santa Ines ewes 26-30 days after mating (Chaves et al, 2020), in Dorper, Shropshire, Hampshire and crosbred (Dorset x Polypay) sheep 30-90 days after mating (Roberts et al, 2019) and in German Blackhead and Merino sheep in mid-pregnancy (range: 71-120 days) (Steckeler et al, 2018). Furthermore, sensitivities similar to the sensitivity determined for the rapid visual PAG ELISA in the present study were reported for the "Idexx visual pregnancy test" in Santa Ines ewes 30 days after laparoscopic insemination (Chaves et al, 2017) and for the "Idexx bovine pregnancy test" in Corriedela and Ile de France x Texel sheep throughout pregnancy (Rovani et al, 2016).…”

“…The presence of PAGs in the maternal circulation allows for an early diagnosis of pregnancy in cows Akköse and Çebi Şen, 2019), sheep (Uçar et al, 2018;Alkan et al, 2020) and goats (Gonzalez et al, 1999;Tandiya et al, 2013 Xie et al (1991) detected immunological and structural similarities between ovine and bovine PAG molecules, it has also been reported that bovine and ovine PAGs can exhibit spatially and temporally distinct expression patterns during pregnancy at species or breed level (Green et al, 2000;Lobago et al, 2009;Mercadante et al, 2013). PAG ELISA pregnancy tests commercially validated for cattle have been used in various Brasilian and European sheep breeds (Rovani et al, 2016;Chaves et al, 2017;Steckeler et al, 2018). It is stated that PAG profiles in the peripheral blood can vary between sheep breeds; therefore, determining the specific PAG profile of breeds native to Turkey is important for improved reproductive management (Kaplan et al, 2019).…”

Plasmatic Profile of Pregnancy-Associated Glycoprotein (PAG) during Gestation and Postpartum in Sarda and Lacaune Sheep Determined with Two Radioimmunoassay Systems

“…These molecules are present in maternal plasma of sheep in concentrations detectable with RIA methods as early as 18-20 days after conception, [3,[11][12][13][14][15][16] and by the enzyme immune assay (EIA) method [17][18][19], as well as in other species of ruminants [1,[20][21][22]. Throughout pregnancy, PAG concentrations in these species differ according to the breed, fetal number, sex and birth weight [3,[23][24][25][26][27][28][29], as in other ruminants [30].…”

Determination of pregnancy protein levels to distinguish between singleton and twin pregnancies in Awassi sheep

“…PAG levels can also be measured in whole blood, serum, plasma, and milk (6,46). In addition to the ELISA method, some researchers have studied PAG levels using the RIA method (6,51).…”

“…This study is compatible with existing research as it used the ELISA method to determine the PAG level by taking blood for measurement starting from day 30 of pregnancy. Studies have shown that the bovine PAG kit can be used for PAG measurement in sheep (39,46). This is because PAG molecules released from trophoblast cells in the placenta of ruminant cattle and sheep have a similar molecular structure, and the cDNA encoding PAG has 86% nucleotide similarity (39).…”