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

Abstract

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 63days p.p.-the previous breeding history should therefore always be taken into account for correct interpretation of the test results.