71 The relationships of late gestational uterine artery blood flow with calf and placental size

Abstract

Abstract Utilizing crossbred fall-calving beef females over 2 years, relationships of uterine artery blood flow (UBF) with cow BW, calf birth BW, and placental characteristics were investigated. Transrectal color Doppler ultrasonography of both uterine arteries was conducted, and scans were grouped into 80, 60, 40, and 20 ± 5 d prior to calving (DPC; n = 28, 38, 36, and 24, respectively). Placentas were dissected post-expulsion (n = 21, 26, 26, and 19, respectively). Correlation coefficients were determined for UBF with BW and placental measures at each timepoint. Total UBF had a moderate positive (80, 40, and 20 DPC, P ≤ 0.009) or weak positive correlation (60 DPC, P = 0.02) with calf BW. Calf BW had a moderate positive correlation (P ≤ 0.04) with contralateral UBF (80, 60, and 40 DPC). Cow BW was not correlated (P ≥ 0.07) with UBF. Total and contralateral UBF had moderate positive correlations (P ≤ 0.03) with cotyledonary, intercotyledonary and total placental weights at 40 DPC and with intercotyledonary weight at 20 DPC. Contralateral UBF had a moderate positive correlation (P = 0.03) with total placental weight at 20 DPC. Ipsilateral UBF had no relationship (P ≥ 0.06) with calf or placental weights. Cotyledon number had a moderate negative correlation (P = 0.02) with ipsilateral UBF at 20 DPC, but a moderate (60 and 80 DPC) or strong (20 and 40 DPC) positive correlation (P ≤ 0.05) with contralateral UBF. Average cotyledonary size had a moderate positive correlation (P = 0.01) with total UBF at 20 DPC. Ipsilateral UBF had a moderate (80 and 40 DPC, P ≤ 0.04) or strong positive correlation (20 DPC, P = 0.003) with average cotyledonary size. These data suggest that late gestational UBF drives fetal and placental growth. Interestingly, contralateral UBF may have a disproportionately greater contribution.