Influence of metabolic status and genetic merit for fertility on proteomic composition of bovine oviduct fluid.

The oviduct plays a crucial role in fertilization and early embryo development providing the microenvironment for oocyte, spermatozoa, and early embryo. Since dairy cow fertility declined steadily over the last decades, reasons for early embryonic loss have gained increasing interest. Analyzing two animal models, this study aimed to investigate the impact of genetic predisposition for fertility as well as of metabolic stress on the protein composition of oviduct fluid (OF). A metabolic model comprised maiden Holstein heifers (MH) and postpartum lactating (Lact) and non-lactating (Dry) cows, while a genetic model consisted of heifers from the Montbéliarde (MBD) breed and Holstein heifers with low (LFH) and high (HFH) fertility index. In a holistic proteomic analysis of OF from all groups using nano-LC-MS/MS analysis and label-free quantification, we were able to identify 1976 proteins, amongst which 143 showed abundance alterations in the pairwise comparisons within both models. Most differentially abundant proteins were revealed between LFH and MBD (52) in the genetic model and between Lact and MH (19) in the metabolic model, demonstrating a substantial effect of genetic predisposition for fertility as well as metabolic stress on the OF proteome. Functional classification of affected proteins revealed actin binding, translation and immune system processes as prominent GO clusters. Notably, Actin-related protein 2/3 complex subunit 1B (ARPC1B) and the three immune system-related proteins SERPIND1, IGK protein and Alpha-1-acid glycoprotein (AGP) were affected in both models, suggesting that abundance changes of immune-related proteins in OF play an important role for early embryonic loss.