Comparative gross and histological morphology of goat (caprine) and sheep (ovine) placentomes

Abstract

This study aimed to investigate the gross and micro-anatomy of the placentome of Tanzanian goats and sheep and their relationship with some foetal parameters. Forty pregnant uteri (20 from goats and 20 from sheep) were collected from slaughtered pregnant animals. Foetal age was estimated using Crown-Rump Length formula. Other parameters such as head length (HL), neck length (NL), fore and hind limb length, foetal weight, total number of placentomes and placentome size and location in the uteri were taken. All placentae exhibited the typical characteristics of a cotyledonary with discrete areas of attachment between maternal and foetal tissues. Placentome counts ranged from 70 to 92 and 74 to 104 in  sheep and goats, respectively. The average length of placentomes was 20.0±4.2 and 30.7±9.0 in sheep and goats, respectively. Placentomes from does in the present study were concave in shape and the majority were of type A. Regression analysis showed a statistically significant relationship  between foetal age and placental size (r2=0.3245; p<0.001); between foetal age and foetal weight (r2=0.7364; p<0.001); and between foetal age and placental weight (r2=0.6458; p<0.01); but the number of placentomes insignificantly (P>0.01) varied with foetal age. In conclusion, this study has demonstrated that the Tanzanian sheep and goat placentae are cotyledonary – synepitheliochorial type having placentomes that tend to increase in  size with gestation age in response to greater nutrient and or metabolic requirement of the growing foetus.