Relationship between placentome diameter and ovine placental lactogen hormone levels in pregnant ewes

This doctoral thesis elucidates the intricate temporal dynamics governing the relationship between placental morphometric development and endocrine functionality throughout ovine gestation, employing a comprehensive longitudinal investigation spanning the critical phases of pregnancy. The research addresses a fundamental gap in veterinary reproductive physiology by characterizing the evolving correlations between placentome diameter and ovine placental lactogen (oPL) concentrations, thereby advancing our understanding of maternal-fetal interface dynamics essential for optimizing reproductive management strategies in contemporary sheep production. The methodological framework incorporated a rigorous longitudinal design featuring sequential ultrasonographic assessments utilizing both transrectal and transabdominal approaches, strategically complemented by systematic blood sampling protocols for oPL quantification across twelve discrete temporal intervals extending from gestational day 26 through day 145. Placentome morphometric analyses and serum oPL determinations were subjected to Pearson correlation analysis to delineate stage-specific associations, with particular attention to the heterogeneous nature of placental development across gestational phases. The investigation revealed a remarkable temporal heterogeneity in placentome-oPL relationships, characterized by three distinct phases of placental-endocrine interaction. Early gestation (D26-D40) demonstrated an absence of significant correlation, reflecting the developmental asynchrony between structural placental growth and endocrine maturation. Mid-gestation (D54-D68) exhibited intriguing negative correlations (r ≈ -0.34, P < 0.05), suggesting a transitional phase wherein morphometric expansion temporarily outpaces hormonal synthesis capacity. Conversely, late gestation (D96-D145) manifested robust positive correlations (r = 0.535-0.593, P < 0.001), indicative of synchronized placental structure-function relationships. Concomitantly, oPL concentrations demonstrated progressive elevation from 5.64 ± 1.86 µg/mL to peak values of 15.60 ± 5.32 µg/mL, while placentome diameter exhibited corresponding expansion from 1.26 ± 0.53 cm to 4.21 ± 0.68 cm. These findings fundamentally challenge conventional assumptions regarding uniform placental development, instead revealing that structural morphogenesis and endocrine maturation follow distinctly regulated temporal trajectories, with functional synchronization emerging as a hallmark of late gestational physiology. The research establishes a novel paradigm for veterinary obstetric practice by providing evidence-based frameworks for enhanced pregnancy monitoring protocols and contributes substantially to the theoretical foundation underlying precision reproductive management in ovine production systems, with broader implications for ruminant reproductive biology.