Compromised development of calves (Bos gaurus) derived from in vitro-generated embryos and transferred interspecifically into domestic cattle (Bos taurus)

Advanced reproductive technologies, incuding IVF and interspecies embryo tr ansfer, are becoming increasingly important for the preservation of endange red species. Previous attempts at interspecies transfers between Bos gaurus and Bos taurus have yielded compromised offspring. The goal of this invest igation was to characterize the effects of interspecies transfer of IVF-der ived embryos on subsequent neonatal outcome. To achieve this goal, fresh Bo s gaurus IVF-derived embryos were transferred into Holstein (Bos taurus) re cipients. Four fetuses were carried to term. Calf weight, temperature, hear t rate, and respiration rate were recorded after birth. Blood samples also were obtained for determination of blood glucose, pH, packed cell volume (P CV), total hemoglobin (tHB), Po-2, and Pco(2). After parturition, milk prod uction and health status of the recipients were recorded. Two calves were a live at birth, and two calves were stillborn. One of the calves that was bo rn alive died within minutes after birth, while the other lived until appro ximately 26 h of age. Blood samples obtained from the calf that lived for 2 6 h showed it to be extremely acidotic and hypoglycemic; this calf also had marked difficulty thermoregulating. At necropsy, all calves showed evidenc e of in utero gasping and hypoxia, suggestive of premature placental separa tion. None of the recipient cows showed typical signs of impending parturit ion. After parturition, lactogenesis in all recipient cows was markedly dec reased. On gross examination, placentae resulting from the interspecies tra nsfers had fewer cotyledons that were also much larger in size compared to cotyledons from normal gaur placentae. Calves in this study had abnormaliti es consistent with those noted from previous interspecies transfers and wit h IVF and nuclear transfer (cloned) carves. Due to the design of this study , it is not possible to differentiate between problems resulting from the I VF process and those resulting from potential interspecies incompatibilitie s. However, interspecies transfers of in vitro-produced gaur embryos into B os taurus are strongly discouraged. (C) 2001 by Elsevier Science Inc.