The effects of non-genetic factors on the morphometric parameters of sheep placenta and the birth weight of lambs

The objective of this study was to determine morphometric parameters of sheep placenta and the birth weight of lambs and their relationship with the type of pregnancy, litter sex and age of ewes. Placenta was obtained directly after delivery from Pomeranian sheep (n=128), including single (n=99) and multiple (n=29) pregnancies. For twin pregnancies, monochorionic and dichorionic placentas were taken into account. The following were determined: lamb birth weight (BWL), placental weight (PW), placental length (PL), placental width (WP), cotyledons number (CN), cotyledons weight (CW), mean diameter of the cotyledon (MDC), umbilical cord diameter (DUC). One-way ANOVA variance analysis was used for statistical comparisons and the Pearson and/or Spearman's correlation coefficient for correlation analysis. The primiparous were shown to have significantly lower PW and MDC (p<0.05) compared to older sheep. On the other hand, in the case of PL (p<0.05) and CN (p<0.01), which were significantly higher in the primiparous compared to multiparous. A significantly higher BWL was found in the male lambs than in the female lambs (p<0.05). Significantly higher PW, MDC (p<0.01) and CW (p<0.05) were found in the placenta from which male lambs were born. There was also a significantly higher BWL in male lambs (p<0.05) born from dichorial twin pregnancy. CW was significantly higher in the dichorial placenta from which the male lambs were born (p<0.05). Comparing the placenta from single and twin dichorial pregnancies, it was shown that type of pregnancy had a significant impact on the development of some placental indices and the birth weight of lambs. Significantly heavier lambs were born from single pregnancy (p<0.01). Also PW and PL (p<0.01) and CN (p<0.01) were significantly higher in single pregnancy placentas. In turn, MDC (p<0.05) was significantly higher in twin placental dichorial pregnancies. Monochorial placenta were characterized by significantly larger PW and CW (p<0.05) from which the male lambs were born. The obtained results showed that morphometric parameters of sheep placenta and birth weight of lambs depend on the type of pregnancy, litter sex and age of ewes. These results may be helpful in assessing postpartum placenta in this animal species. In addition, recorded differences in placenta parameters and birth weight of lambs may be useful in ultrasound assessment of placental and fetal development during pregnancy.