Placental samples for RNA extraction are collected via invasive methods (post-mortem or surgically) in small ruminants. An alternative could be using delivered placentas, but the feasibility of obtaining high-quality RNA from this tissue has not been determined. We aimed to evaluate the possibility of extracting RNA from naturally delivered ovine placenta, comparing two preservation methods. Twenty-seven single-pregnant sheep were monitored 24/7 from gestational day 140 to parturition. Tissue was collected immediately after placental delivery, preserved using Snap Frozen (SF, n=27) and RNAlater® (LTR, n=27) techniques, and processed for RNA extraction using a commercial kit. RNA concentration (ng/uL), A260/280, and RNA Quality Number (RQN) were measured. Concentration was higher (p < 0.001) in LTR (70.39 ± 6.3) than in SF (49.77 ± 10.5), A260/280 was higher (p = 0.045) in SF (2.06 ± 0.01) than in LTR (2.03 ± 0.01), and RQN was higher (p < 0.0001) in SF (6.81 ± 0.24) than LTR (2.84 ± 0.24) samples. The timing of placental delivery did not affect the evaluated indicators. Our results indicate that extracting high-quality RNA from delivered placenta preserved via snap frozen technique is possible, supporting a method that aligns with the refinement principle of animals used in research.

Placental samples for RNA extraction are collected via non-recovery (euthanasia) or invasive (surgery) methods in small ruminants, such as sheep. Alternatively, delivered placentas could be used, but the feasibility of obtaining high-quality RNA from this tissue is unknown in sheep. We aimed to evaluate the possibility of extracting RNA from naturally delivered ovine placenta, comparing two preservation methods. Twenty-seven single-pregnant sheep were monitored 24/7 from gestational day 140 to parturition. Tissue was collected after placental delivery, preserved using snap frozen (SF, n = 27) and RNAlater^® (LTR, n = 27) techniques, and processed for RNA extraction using a commercial kit. RNA concentration (ng/µL), A260/280, and RNA quality number (RQN) were measured. Concentration was higher (p < 0.001) in LTR (70.39 ± 6.3) than in SF (49.77 ± 10.5), A260/280 was higher (p = 0.045) in SF (2.06 ± 0.01) than in LTR (2.03 ± 0.01), and RQN was higher (p < 0.0001) in SF (6.81 ± 0.24) than in LTR (2.84 ± 0.24) samples. Timing of placental delivery did not affect the evaluated indicators. Results indicate that extracting high-quality RNA from delivered placentas preserved via the snap-frozen technique is possible, supporting a method that aligns with the refinement principle of animals used in research.

In rangeland systems, natural nutrient restriction (NR) elevates risk for small-for-gestational-age (SGA) lambs, yet some NR ewes deliver Non-SGA offspring. We evaluated whether fetal biometry and Doppler indices could differentiate those fetal growth trajectories. Ninety-five single-pregnant Corriedale ewes were assigned from gestational day (GD) 70 to term to NR grazing (n=72) or supplemented Controls (n=23) groups. Fetal biparietal diameter (BPD), femur length (FL), thoracic height (TH), and umbilical cord diameter (UCD) were assessed at GD80, GD95, GD110, and GD125. Resistance (RI) and pulsatility (PI) indices were recorded for the umbilical (UA), cotyledonary (CA), and uterine (UtA) arteries at GD80, GD95, GD110, GD125, and GD140. Within NR, offspring were stratified by birth-weight (BW) quartiles to define SGA (lowest quartile, n=18) and Non-SGA (highest quartile, n=18) groups. Prenatal biometry did not differ among groups. At birth, BW differed (p < 0.05) among Control (4.95 ± 0.10 kg), Non-SGA (5.33 ± 0.06 kg), and SGA (3.79 ± 0.11 kg), and BPD and FL were smaller in SGA vs Control and Non-SGA. UA-RI at GD125 was higher in SGA vs Non-SGA (p < 0.005). UtA-RI and UtA-PI were lower in mothers of SGA lambs at GD110 and GD125 (p < 0.05). CA indices did not differ. UA-RI at GD125 was associated with BW (R² = 0.15; p < 0.001). Associations between BW and UtA-RI and UtA-PI at GD 110 and 125 explained little variance (R² ≤ 0.08). Distinct uteroplacental and umbilical Doppler signatures differentiated SGA from Non-SGA trajectories before measurable divergence in fetal growth. Although UA-RI at GD125 demonstrates prenatal predictive promise, its accuracy as standalone indicator remains modest.

Nutrient restriction (NR) increases small-for-gestational-age (SGA) offspring; however, some NR ewes deliver Non-SGA lambs. We evaluated whether fetal biometry and Doppler indices could distinguish divergent fetal growth trajectories. Ninety-five single-pregnant Corriedale ewes were assigned to NR grazing (n = 72) or supplemented Controls (n = 23) from gestational day (GD) 70 to 140. Fetal biparietal diameter (BPD), femur length (FL), thoracic height (TH), umbilical cord diameter (UCD), and resistance (RI) and pulsatility (PI) indices in umbilical (UA), cotyledonary (CA), and uterine (UtA) arteries were assessed at several GDs. Offspring within NR group was stratified by birth weight (BW) quartiles as SGA (n = 18) or Non-SGA (n = 18). At birth, BW differed (p < 0.05) among Control (4.95 ± 0.10 kg), Non-SGA (5.33 ± 0.06 kg), and SGA (3.79 ± 0.11 kg), with reduced BPD and FL in SGA lambs. Prenatal biometry did not differ. UA-RI at GD125 was higher in SGA (p < 0.005) and associated with BW (R² = 0.15; p < 0.001). UtA indices were lower in SGA at GD110 and GD125 (p < 0.05) but weakly associated with BW (R² ≤ 0.08). Doppler differences were detected before measurable growth divergence but have modest predictive value.