Markers for early pregnancy prediction in Zebu cows subjected to timed artificial insemination

Context To increase the number of cows pregnant in the early breeding season, strategies have been developed that seek to reduce the interval for pregnancy diagnosis. Aims The aim of this study was to evaluate markers for the early detection of pregnancy in Zebu cows. Methods A total of 175 Zebu cows were assessed at the time of insemination for the follicle diameter (FOLD), follicular wall area (FOLA) and follicle blood flow (FOLV). Twenty days after fixed-time artificial insemination (TAI), the corpus luteum was evaluated for diameter (CLD), area (CLA), vascularized area (CLV), and percentage of vascularization (%CLV). Blood samples were also collected to measure progesterone levels 20 days after insemination (P4D20). On the basis of FOLD, FOLV, CLD, CLV, and P4D20 as potential early pregnancy markers, the animals were categorized into two groups: negative predictive diagnosis of pregnancy (NPD) and positive predictive diagnosis (PPD). A definitive pregnancy diagnosis was performed 30days post-TAI. Key results Pregnant cows exhibited higher FOLD, FOLA, FOLV, CLD, CLA, CLV, %CLV, and P4D20 levels compared to non-pregnant cows. Significant correlations were found between FOLD and FOLA, FOLV, percentage of follicular vascularization (FOLV%), CLD, CLA, CLV, %CLV, and P4D20. FOLA was also significantly correlated with FOLV, CLD, CLA, CLV, %CLV, and P4D20. Similarly, FOLV was significantly correlated with FOLV%, CLD, CLA, CLV, %CLV, and P4D20. CLD correlated significantly with CLA, CLV, %CLV, and P4D20, while CLV showed significant correlations with %CLV and P4D20. Conclusions The follicular and luteal morphofunctional characteristics are intricately linked to pregnancy establishment. Implications The CLV emerged as a promising marker for achieving earlier pregnancy diagnoses.