Echo-Doppler ultrasonographic assessment of resistance and velocity of blood flow in the ductus venosus throughout gestation in fetal lambs.

It has been postulated that during fetal hypoxia, the blood flow shunted through the ductus venosus increases and may account for upto 70% of the total umbilical flow. The objectives of the present study were to use ultrasonography to determine the velocities and waveform indices of blood flow in the ductus venosus in the fetal lamb. The ductus venosus of 15 lamb fetuses was evaluated weekly from Days 45 to 143 of gestation (Day 0=day of AI). The Doppler indices measured were: S/D, the systole/diastole ratio; RI, the resistance index; and PI, the pulsatility index. The velocity waveforms studied were: SV, the peak velocity during ventricular systole; D, the peak velocity during ventricular diastole; aV, the lowest forward velocity during atrial contraction; and TAMV, the time-averaged maximum velocity. Doppler indices from Days 52 to 143 were highly correlated: S/D versus PI (r=0.96, P<0.0001), and versus RI (r=0.93, P<0.0001); and PI versus RI (r=0.97, P<0.0001). Velocity indices were also positively correlated: velocity SV versus D (r=0.87, P<0.0001), versus aV (r=0.79, P<0.05), and versus TAMV (r=0.98, P<0.0001); D versus aV (r=0.88, P<0.05), and versus TAMV (r=0.87, P<0.05); and aV versus TAMV (r=0.82, P<0.05). Doppler indices were negatively correlated with SV (r=-0.22, P<0.03); D (r=-0.37, P<0.0001); TAMV (r=-0.32, P<0.05) and with aV (r=-0.67, P<0.05). The mean value of each Doppler index decreased 40% from Days 52 to 73 (e.g., PI from 0.82+/-0.08 to 0.51+/-0.10; P<0.05), with no significant changes thereafter. Mean (+/-S.E.M.) values of velocity indices SV, D, aV, and TAMV rose twofold from Days 60 to 115 of gestation (e.g., SV from 54.4+/-8.8cm/s to 104.9+/-19.7 and aV from 24.8+/-6.9 to 54.9+/-5.9; P<0.05). In conclusion, Doppler ultrasonography facilitated assessment of the blood flow pattern in the ductus venosus in lamb fetuses between Days 52 and 143.

How healthy are clones and their progeny: 5 years of field experience.

There is considerable concern regarding the health of cloned cattle and their safety as a source of food. The objective was to summarize 5 years of commercial experience with cloning in three countries (United States, Argentina and Brazil). Overall, only 9% of transferred embryos resulted in calves; efficiency ranged from 0 to 45% (most were from 1 to 10%, but 24% of cell lines never produced live calves). There was no significant difference in pregnancy rate following transfer of one versus two embryos. Before 90 days of gestation, two ultrasound markers for embryo death were found, either crown rump length (CRL) or heart beat less than 7.5mm and 150bpm, respectively, were observed alone or together in 27% of clones that died. In addition, after 100 days of pregnancy, placental edema, hydrops fetalis and increased abdominal circumference size were used as ultrasound findings of a fetus at risk of loss. At 114 days of gestation, abdominal circumference in clones that died was statistically larger than in clones that survived alive to term and from MOET- and IVF-derived pregnancies (P<0.05). Since elective cesarean section (C-section) was partially replaced by natural or assisted parturition, C-section rates decreased from 100% in 2000 to 54% in 2005. On average, 42% of cloned calves died between delivery and 150 days of life; the most common abnormalities were: enlarged umbilical cord (37%), respiratory problems (19%), calves depressed/prolonged recumbency (20%) and contracted flexor tendons (21%). From 11 blood parameters evaluated during the first week of life, lactate decreased twice and glucose doubled its original value from 24h to 7 days. Adult cloned females had normal breeding and calving rates and cloned bulls produced good quality semen and had normal fertility when used for AI or natural mating. In conclusion, cloning had no risks qualitatively different from those encountered in animals involved in modern agricultural practices, although the frequency of the risks appeared to be increased in cattle during the early portions of the life cycle of cattle clones.

Transrectal Doppler sonography for evaluation of uterine blood flow throughout pregnancy in 13 cows.

Once weekly from 30 to 270 days of gestation in 13 cows, Doppler ultrasound scanning (triplex Doppler system) was done to assess blood-flow parameters of both median uterine arteries. Resistance, velocity and volume indices were measured. Resistance index values were negatively correlated to all other blood-flow parameters (P<0.05), but there were positive correlations between velocity and volume indices (P<0.05). Resistance indices were lower, and velocity and volume indices were significantly higher in the median uterine artery ipsilateral versus contralateral to the fetus. Resistance indices decreased continuously during the first 36 weeks of pregnancy. Velocity values rose three-fold, whereas the area increased 20-fold and the volume increased 17-fold by the end of gestation (P<0.05). Birth weight of calves was positively correlated with blood-flow volume (r=0.34) but negatively correlated with the resistance index (r=-0.45). There were no significant differences between male versus female calves (at any stage of gestation) in the resistance, time-average maximum velocity, and volume indices (P>0.05). In conclusion, arterial blood flow was monitored with transrectal Doppler sonography in both median uterine arteries weekly throughout pregnancy in cattle; this could be very valuable for monitoring pregnancies at high risk for abnormalities of the placenta, fetus or both, e.g. cloned calves.