Transabdominal ultrasound for detection of pregnancy, fetal and placental landmarks, and fetal age before Day 45 of gestation in the sheep

Abstract

Detection of pregnancy during early gestation is advantageous for flock breeding management. Transabdominal ultrasound is a practical and efficient approach for monitoring pregnancy and fetal growth in small ruminants. However, there is limited information using the transabdominal technique before day (d) 45 of gestation in sheep. Therefore, our objective was to determine how accurately transabdominal ultrasound could be used to detect pregnancy, to identify pregnancy landmarks, and to quantify fetal length before d 45 in ewes. Multiparous Western White-faced ewes (n = 99) were estrus synchronized and exposed to one of four Dorset rams. The day a ewe was marked by a ram was considered d 0 of gestation. Ewes not remarked by d 20 were separated for ultrasonography. To detect pregnancy and landmarks, ewes were scanned three times per week between d 26.0 ± 0.3 (mean ± standard error) and d 40.0 ± 0.2. A single technician performed all scans in the right non-haired abdominal pit using a real-time portable EasiScan machine and a 5 MHz linear rectal transducer. All data were analyzed using the MIXED procedure in SAS (with repeated measures where appropriate). Due to rebreeding activity, 113 ultrasound periods were initiated. The specificity and positive predictive value were 100% during the entire study. The accuracy, sensitivity, and negative predictive value of ultrasound scanning were greater than 90% beginning at d 33 ± 1. On average, pregnancy (n = 85) was detected at d 28.7 ± 0.4 and non-pregnancy (n = 28) at d 25.5 ± 0.6. Three early fetal losses were identified at d 39.7 ± 0.7. In pregnant ewes (n = 82) the overall accuracy of fetal counting was 78%. The first observance of an enlarged uterus (P = 0.05) and pregnancy (P = 0.03) were detected earlier when multiple fetuses were developing compared with singletons. Placentome evagination was first observed earlier in triplets compared with twins and singletons (P = 0.02). Fetal length increased with day of gestation (P < 0.0001), but not fetal number (P = 0.72). A fetal number by day of gestation interaction (P = 0.01) indicated differences in fetal length at d 29 ± 1 and d 32 ± 1. These data demonstrate that a portable ultrasound using the transabdominal technique can be used to accurately determine pregnancy, identify landmarks indicative of gestation, and estimate fetal age, before d 45 of gestation in sheep.

Evaluation of a bovine visual pregnancy test for the detection of pregnancy‐associated glycoproteins in sheep

“…Two sheep in experiment 1 were diagnosed as pregnant by ultrasonography as well as the visual‐PAG‐test but no parturition was observed in our study. The sensitivity of transabdominal ultrasonography is described as 100% from day 39 of gestation onwards (Jones et al, ), and the sheep were scanned by a skilled and experienced veterinary surgeon. Pregnancy diagnosis was based on the presence of clear foetal fluid, placentomes and foetal body parts, which are easily identifiable in mid to late gestation.…”

“…A variety of methods can be used for pregnancy diagnosis in sheep; one of the most common methods is transabdominal ultrasonography. While it can be performed from day 21 of pregnancy with a sensitivity of 44.4%, it is commonly used from day 35 onwards and has shown a sensitivity of 100% from day 39 of gestation (Jones et al, ). Other methods include transrectal ultrasonography, radiography and different hormonal assays which are well described and reviewed by Karen, Kovács, Beckers, and Szenci ().…”

Effects of maternal nutrition on the expression of genomic imprinted genes in ovine fetuses

“…All animal protocols [58,59] were reviewed and approved by the University of Connecticut Institutional Animal Care and Use Committee. Animal breeding, feeding, and sample collection were described in Pillai et al, 2017.…”

“…Ewes were individually housed beginning 20 days after mating. Pregnancy was confirmed by ultrasound at day 28.5 ± 0.4 of gestation [58] if a ewe was not re-marked by a ram; day 0 represents the initial marking of the ewe by the ram. On day 30 of gestation, pregnant ewes were randomly assigned to control 100% (Con), restricted 60% (Res) or overfed 140% (Over) based on the National Research Council (NRC) total digestible nutrients (TDN) for ewes pregnant with twins.…”

Progesterone promotes fetal growth in a restricted interspecies gestation (Ovis canadensis x Ovis aries)

“…The diagnosis of gestation was carried out by transrectal ultrasonography with a linear 7.5 MHz transducer at day 30 post-insemination and confirmed by transabdominal ultrasonography with a linear 5 MHz transducer at day 40. [28][29] Progesterone levels were measured once a week from only six females with single gestations from each group from weeks 6 to 22 of gestation. Blood samples were obtained by venipuncture from the jugular using vacutainer tubes and needles.…”