Hormonal and Metabolomic Signatures of Embryo Loss in Friesian-Zebu Crossbred Cattle in South West Nigeria: Towards a Predictive Biomarker Framework

Early embryo loss between conception and day forty-five of pregnancy is a major cause of reduced calving rates in Nigerian dairy cattle, and predictive biomarker frameworks that could identify at-risk cows before embryo loss occurs are absent from the literature. This doctoral study characterised the hormonal and metabolomic signatures associated with subsequent embryo loss in Friesian-Zebu crossbred cattle at commercial farms in Lagos and Ogun States, South West Nigeria, and developed a predictive biomarker framework. One hundred and fifty cows confirmed pregnant by transrectal ultrasonography at day twenty-five post-insemination were monitored through day forty-five. Forty-four cows experienced embryo loss between days twenty-five and forty-five. Serum progesterone, oestradiol, prostaglandin F2-alpha metabolite, interferon-tau, and insulin were measured at days twenty-five, thirty, and thirty-five of gestation. Serum untargeted metabolomics was performed by ultra-performance liquid chromatography-mass spectrometry at day twenty-five. Cows that subsequently lost embryos had significantly lower progesterone at day thirty and higher prostaglandin F2-alpha metabolite at day twenty-five compared to cows maintaining pregnancy. Interferon-tau was significantly reduced in loss cows at day thirty, indicating impaired conceptus-mediated maternal recognition of pregnancy. Metabolomic profiling identified a distinct pre-loss signature characterised by elevations in ceramides, lysophosphatidylcholines, and sphinganine at day twenty-five. A combined hormonal-metabolomic biomarker panel predicted embryo loss with 84% sensitivity and 88% specificity at day twenty-five. This doctoral study provides an actionable predictive framework for early embryo loss intervention strategies in South West Nigerian dairy operations. Keywords: embryo loss, progesterone, metabolomics, interferon-tau, Friesian-Zebu cattle.