Pathological features of cloned calves that died in the neonatal period

Abstract

Somatic-cell nuclear transfer is a cloning technique that enables the creation of a viable embryo from a donor adult to produce a genetically identical individual. This technique opens numerous potential possibilities for medicine and animal reproduction. However, several reports have documented cloning-related issues. Embryo and fetal losses remain significantly higher than in other techniques, and there is a high incidence of dystocia and hydrops, which decreases efficiency and increases costs. Animals delivered at term often exhibit a syndrome known as macrosomia and experience difficulties in adapting to life outside the uterus, and death is a common outcome. In the present study, 41 cloned calves that died in the neonatal period were subjected to gross and histopathological examination. Most important gross lesions were found in the liver (enlargement, congestion, yellowish color), kidneys (brownish color at surface and cut, and cysts), lungs (atelectasis, parenchymal consolidation, and secretions in bronchi and bronchioles), and heart (concentric and eccentric hypertrophy, hematic cysts, persistence of ductus arteriosus). Primary microscopic findings were seen in the liver, kidneys, and lungs from neonatal calves. In the liver, 85% of the animals exhibited hepatic degeneration. The presence of a brownish pigment within the cortical tubules of the kidneys was found in approximately 90% of the samples; the presence of this pigment has not been previously reported in cloned calves. In the lungs, a large number of animals exhibiting lesions characteristic of pneumonia (55%). These changes were the pivotal causes of death, mainly due to problems in adapting to life outside the uterus and opportunistic infections in the neonatal period. Further investigation focusing on pathological anatomical changes is necessary to map these abnormalities in cloned animals.