Review/Oorsig Volume 22, Issue 04 - Page 6

Oorsig/Review to placental efficiency and fetal growth and should weigh between 4 to 8 kg and be ±14% of the fetus/stillbirth weight. Cotyledon number varies between 75 to 120, with the average cotyledon diameter of 4 cm when fully developed at ± 175 days. Reduced cotyledon numbers are associated with placental insufficiency in the bovine (figure 4). Figure 7 - cut surface cotyledon, acute infarcts.jpg Figure 5 – complete ovine placenta Examine cotyledons for evidence of adherent caruncule tissue, hemorrhage, necrosis, infarction and suppuration (figure 6). To evaluate for infarcts section through cotyledons to expose cut surfaces. Presence of infarcts may suggest mycotic infection or vasculitis (figure 7). Examine inter-cotyledonary areas for thickening, Placental weight and cotyledon numbers (80- 100) in small ruminants on the other hand, are poorly related to fetal growth, with blotted cotyledon weight being a more reliable indicator of placental development and efficiency plus fetal growth. Cotyledons reach their maximum size at around 90 days of gestation. Total cotyledonary weight varies from 115-130g with an average single cotyledon weight of 1.6-1.8g (figure 5). If available, the entire placenta should be examined because lesions of placentitis may be regional. In the normal fresh placenta cotyledons are red while the inter-cotyledonary areas have a clear translucent appearance. However, beware of the effects of post mortal autolysis where the cotyledons become dull brown and the intercotyledonary zones less translucent. Figure 8 - thick leathery exudate in the intercotyledonary area (Coxiella burnetti) increased opacity, surface exudate, proliferation and necrosis (figure 8). Examine umbilical cord for evidence of torsion. To qualify as an ante-mortal event congestion, hemorrhage and edema should accompany the twists (figure 9). The following major causes of abortion in ruminants, frequently only produce placental pathology with no foetal lesions. So, if only the foetus is submitted there is an increased risk they may be missed Figure 6 - toxoplasmosis with cotyledonary necrosis 6 • • • • Brucellosis Coxiella burnetti (Q-Fever) Chlamydia abortus / pecorum Toxoplasmosis