Perinatal physiology in cloned and normal calves: hematologic and biochemical profiles.

Although a majority of clones are born normal and apparently healthy, mortality rates of nearly 30% are described in many reports. Such losses are a major limitation of cloning technology and represent substantial economic investment as well as justifiable animal health and welfare concerns. Prospective, controlled studies are needed to understand fully the causes of neonatal mortality in clones and to develop preventive and therapeutic strategies to minimize losses. We report here the findings of studies on the hematologic and biochemical profiles of cloned and control calves in the immediate 48-h postpartum period. Cloned calves were similar to control calves for a majority of parameters studied including blood gases, concentrations of plasma proteins, minerals and electrolytes, and white blood cell, neutrophil, lymphocyte, and platelet counts. The most notable differences between clones and controls in this study were reduced red- and white-blood cell counts in clones at birth and 1 h of age. As a group, plasma electrolyte concentrations were more variable in clones, and the variability tended to be shifted either higher (sodium, chloride) or lower (potassium, bicarbonate) than in controls. Previously, we noted differences in carbohydrate parameters, the length of time required for clones to make the neonatal adaptation to life ex utero, and morphology of the cloned placenta. Taken together, our findings suggest that cloned calves experience greater difficulty adjusting to life ex utero and that further research is warranted to determine the nature of the relationship between the physiological differences noted here in clones at birth and concomitant abnormal placental morphology.