The usefulness of placentome diameter measurement for the determination of gestational age in Nigerian breed of sheep and goats was investigated in two experiments. In the first experiment, cross-sectional design was used and placentome diameters were measured in 18 Yankasa/Uda crossbred ewes and 20 Sahel does using trans-abdominal probe. A tentative estimate of gestation age was made using placentome diameter and gestation age correlates from a previous study. Subsequently, the date of parturition was recorded for each animal and the actual conception date was calculated retrospectively using a previously described 148-day gestation table for ewes and does. In the second experiment, a prospective cohort design was used on 6 goats, from end of second trimester until parturition. The date of conception was then retrospectively calculated. It was found that the estimated and actual gestation ages in both sheep and goats were not significantly different (P>0.05). The correlation coefficient (r²) between the placentome diameter and gestation age was 0.84 (P= 0.0001), for sheep and 0.90 (P= 0.0001) for goats suggesting a significant high positive correlation between placentome diameter and gestational age. The regression equation was y=2.809x+7.555 and y=2.930x+9.611 for sheep and goats, respectively. However, the placentome diameters monitored until parturition were not significantly different (P>0.05) between the weeks and not significantly correlated with gestational age. It was concluded that placentome diameter is useful to estimate gestational age at mid gestation and not within the last third of pregnancy.
Key words: Gestational age, Goat, Placentome diameter, Sheep, Ultrasonography
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