Pregnancy in cattle and sheep can be diagnosed by the presence of a conceptus-derived antigen in maternal serum that is secreted by trophoblast and placental tissue primarily as an acidic component of Mr. 67%000. Molecular doning of its cDNA reveals that the antigen belongs to the aspartic proteinase family and has >50% amino add sequence identity to pepsin, cathepsin D, and cathepsin E. The inferred sequences of the ovine and bovine polypeptides show -73% identity to each other. Critical amino acid substitutions at the active site regions suggest that both proteins are enzymatically inactive. The antigen is a product oftrophoblast binuceate cells that invade maternal endometrium at implantation sites.

Antigen(s) immunologically related to pregnancy-associated glycoproteins (PAGs) have previously been detected in the serum of pregnant goats. In this work, we describe a partial characterization of a family of PAGs isolated from the placenta of the goat. The procedure, monitored by RIA, included extraction of proteins at neutral pH, acidic, and ammonium sulfate precipitations; and gel filtration and ion exchange chromatographies. Immunoreactivity, initially located in the acidic supernatant and in the 40-80% ammonium sulfate fractions, was equally apportioned between the 0.04 and 0.08 M NaCl DEAE fractions. After further purification of both DEAE fractions, the preparations were subjected to one- and two-dimensional electrophoresis, and individual polypeptides were analyzed by amino acid sequencing. Three PAGs, which differed in amino acid sequence and apparent molecular masses (62, 59, and 55 kDa), were detected, each containing several isoforms with different pls: caprine (c) PAG62 (pl: 5.1, 4.8), cPAG59 (pl: 6.2, 5.9, 5.6), and cPAG55 (pl: 5.3, 5.1, 4.9). These proteins had high sequence identities to each other and to PAGs purified from other species. Each had two putative N-glycosylation sites within the 27 amino terminal residues sequenced. This work demonstrates that PAGs are present in goat placenta and that multiple forms are expressed.

Various practical methods have been used for pregnancy diagnosis in sheep. Both pregnancy and fetal numbers are accurately diagnosed by using radiography after day 70 of gestation. Rectal abdominal technique detects pregnancy with an accuracy of 66 to 100% from d 49 to 109 of gestation, however, it has a low (17 to 57%) accuracy for determining multiple fetuses. Progesterone assays have a high sensitivity (88% to 100%) and a low specificity (60% to 72%) at d 16 to 18. Estrone sulphate assay accurately detects pregnant ewe at d 30 to 35. Ovine pregnancy specific protein B (PSPB) assay accurately (100%) detects pregnancy from d 26 after breeding onwards. The accuracy of progesterone, estrone sulphate and oPSPB assays for determining fetal numbers is relatively low. A-mode and Doppler ultrasonic techniques accurately detect pregnancy during the second half of gestation. Fetal numbers cannot be determined by A-mode ultrasound, while the Doppler technique needs experience to achieve high accuracy. Transrectal B-mode, real time ultrasonography identifies the embryonic vesicles as early as d 12.8 after mating, but the sensitivity of the technique for pregnancy is very low (12%) earlier than 25 d after mating. Transabdominal B-mode ultrasonography achieved high accuracy for pregnancy diagnosis (94% to 100%) and the determination of fetal numbers (92% to 99%) on d 29 to 106 of gestation. Realtime, B-mode ultrasonography appears to be the most practical and accurate method for diagnosing pregnancy and determining fetal numbers in sheep.

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