Review: Initial increase in pregnancy-specific protein B in maternal circulation after artificial insemination is a key indicator of embryonic survival in dairy cows

Lactating dairy cows have reduced chances for pregnancy survival following 1st parturition. It appears that timing of conceptus attachment, defined as an initial daily rise in pregnancy-specific protein B (PSPB) postartificial insemination (AI), is key to the survival of the embryo. PSPB is a protein produced from binucleate cells of the trophectoderm of the conceptus. Once the conceptus has attached to the uterine epithelial cells, this large protein is detectable in maternal circulation. Daily sampling of serum allows for detection of the initial increase of PSPB. A percent increase threshold for PSPB was determined from results from each study using a conservative three-day minimum increase. Thus far, a 10 or 12.5% daily increase for three consecutive days had the greatest sensitivities and specificities for studies reported in this review. Nulliparous heifers receiving AI following estrus appear to have a reduced time to conceptus attachment compared to lactating cows that received either Ovsynch or AI following estrus. Increasing progesterone post-AI did not reduce time to conceptus attachment in lactating cows. Multiparous cows treated post-AI with human chorionic gonadotropin had a reduced percent with conceptus attachment in addition to greater time to conceptus attachment. Increased time to conceptus attachment increased the chances of multiparous cows having embryonic death before 35 d post-AI. Concentrations of PSPB are consistently reduced from conceptus attachment until d 28 post-AI in cows with pregnancy loss compared to cows that maintain pregnancy on d 34 post-AI. This novel model to determine timing of conceptus attachment provides a new perspective on percent of cows pregnant around d 20-23 post-AI and the potential for a greater understanding of subsequent pregnancy loss. (c) 2023 The Author(s). Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Lactating dairy cows have reduced chances for pregnancy survival following 1st parturition. The timing of conceptus attachment, indicated by the initial daily rise in pregnancy-specific protein B (PSPB) post artificial insemination (AI), is crucial for embryo survival. Nulliparous heifers receiving AI after estrus have a shorter time to conceptus attachment compared to lactating cows that received either Ovsynch or AI after estrus. Increasing progesterone post-AI does not reduce the time to conceptus attachment in lactating cows.