Rewiring the Luteal Microenvironment: Hemodynamic and Molecular Insights into eCG-Supported CL development in Indigenous White Lamphun Cattle

This study evaluated the effects of low-dose equine chorionic gonadotropin (eCG) supplementation on follicular dynamics, ovulation, corpus luteum (CL) development, luteal hemodynamics, and angiogenesis-related gene expression in indigenous White Lamphun cows under a short-duration estrous synchronization protocol. Twenty multiparous cows were randomly allocated into two groups: a control group (n=10) and an eCG-treated group (n=10) receiving 200 IU eCG intramuscularly at CIDR removal (Day 0). Daily B-mode ultrasonography revealed significantly faster dominant follicle (DF) growth and larger preovulatory follicle (POF) diameters in the eCG group (p<0.05). CL development assessed on Days 4 and 11 post-ovulation (CL 4 and CL 11) showed greater CL diameter, area, and volume in the eCG group (p<0.01 and p<0.001, respectively). Color Doppler imaging indicated improved luteal hemodynamics, with a higher colored area/total CL area ratio on both CL 4 (p<0.05) and CL 11 (p<0.01). Plasma progesterone (P4) concentrations were significantly elevated at CL 11 (p<0.05), while preovulatory estradiol (E2) levels were also higher in the eCG group (p<0.05). Gene expression analysis of luteal tissues on CL 11 revealed significant upregulation of Notch receptor 4 ( NOTCH4 ), Jagged1 ( JAG1 ), and CD300 molecule like family member G ( CD300LG ) (p<0.05), whereas endothelial nitric oxide synthase ( NOS3 ) and matrix metalloproteinase-9 ( MMP9 ) did not differ significantly between groups (p>0.05). These results indicate that low-dose eCG enhances follicular development, CL function, and luteal angiogenesis, providing a promising strategy to improve fertility in Bos indicus cattle. Lay summary This study tested whether a small dose of equine chorionic gonadotropin (eCG), a hormone naturally produced during pregnancy in horses, can enhance ovarian function in native Thai cattle. We added eCG to a short estrous synchronization program, a hormone-based protocol used to align the timing of ovulation among cows within a few days, and evaluated key reproductive processes: egg release (ovulation), development of the corpus luteum (CL), a temporary gland formed after ovulation that secretes progesterone (P4), a hormone essential for establishing and maintaining early pregnancy, and blood flow to the CL. We also measured hormone levels and the activity of genes involved in forming new blood vessels. Cows that received eCG showed stronger ovarian activity, including larger preovulatory follicles, more robust CL development, better ovarian blood flow, and higher P4 levels. Genes related to vascular growth were also more active. These findings indicate that low dose eCG supports CL function and ovarian physiology and may help improve the efficiency of breeding management in local cattle.