Prediction of pregnancy stage by ultrasonography in the Sarda sheep: a preliminary study
Measures of foetal growth during gestation have been published for several goat and sheep breeds to calculate the estimated gestational stage. Up to date, no study is available in the literature for the Sarda sheep. The aim of this study was to investigate, by ultrasonography, the foetal and placental morphometry in the Sarda sheep. A total of 256 ultrasonographic images were achieved from six ewes from day 24 of pregnancy (D24) to D92. The crown to rump length in cm (CRL) was recorded and, using visual scales score, foetal ossification (1 = absence; 2 = a few; 3 = several ossifications) and development of placental cotyledons (1 = absence; 2 = visible but immature; 3 = mature) were categorised. The data regarding CRL were analysed using a MIXED procedure
while aspects of ossification and cotyledons using the Fisher’s exact test. The effect of the pregnancy stage on CRL was statistically significant (p < 0.001) and all the stages were differentiable each other. The least squares means of CRL spanned from 1.33 (D24 to D30) to 9.85 cm (D55 to D60). The effects of parity and lambing rate on CRL were not significant and the total variance attributable to the random effect of the single sheep was negligible. Based on the aspect of both ossification and cotyledons, it was possible to differentiate pregnancy stages between D31 to D50. These results are useful for veterinarians, in the field of reproductive management of Sarda sheep farms, to provide a consistent prediction of the date of lambing.