Vascularization to preovulatory follicle and corpus luteum-a valuable predictor of fertility in dairy cows

- Predict pregnancy rate based on vascularization to follicle and corpus luteum (CL).
- Cows with a highly vascularized follicle (>550 pixel2) underwent a normal pregnancy.
- Moderately (250-550 pixel2) and poorly (<250 pixel2) vascularized follicle led to complicated or non-pregnancy respectively.
- Assessment of luteal blood flow along with turbulence to blood flow in day 21 CL proved highly valuable.
- Increased turbulence in CL of complicated pregnant cows (66.67%) compared to CL of pregnant cows (16.67%).

The aim of the present study was to predict pregnancy rate based on vascularization to follicle and corpus luteum (CL). 26 Holstein Friesian cows were synchronized using Ovsynch protocol. On day 10 of the protocol, vascularization and morphological characteristics [sectional area (SA), volume (V) and mean diameter] of follicle was assessed and animals underwent artificial insemination (AI). Morphological evaluation and vascularization to CL was assessed on day 12 and 21 following AI and blood samples were obtained for estimation of plasma progesterone (P4). Pregnancy diagnosis was performed on day 60 of AI and was classified as normal, complicated and non-pregnant. The overall conception rate was 76.92% (20/26); normal pregnancy was 53.85% (14/26). Complications observed in pregnancy were intrauterine growth retardation, late embryonic death and infection. Cows with a highly vascularized follicle (>550 pixel2) underwent a normal pregnancy, whereas those that had moderately (250-550 pixel2) and poorly (<250 pixel2) vascularized follicle experienced complicated pregnancy or remained non-pregnant, respectively. On day 12, there was no significant variation (P > 0.05) between mean diameter, SA, V, luteal blood flow (LBF) or plasma P4 concentration among CL of cows that remained pregnant (PCL), non-pregnant (NPCL) or that had a complicated pregnancy (CPCL). LBF alone was not beneficial in differentiating among the three groups (P > 0.05), but assessment of LBF along with turbulence to blood flow in day 21 CL proved highly valuable due to an increased turbulence in CPCL (66.67%) compared to PCL (16.67%). Assessment of turbulence and LBF on day 12 and 21 can also be used to predict luteolysis with accuracy.