Protein energy malnutrition and fat mobilization in neonatal calves.

Fat stores and organ weights were assessed in calves at birth (n=5) and after seven days of milk (n=5) or electrolyte (n=5) feeding.Compared to newborn calves, milk-fed calves had a significant (p < 0.05) redistribution of fat from perirenal area to bone marrow. The thymus also involuted during milk feeding.In electrolyte-fed calves there was a significant loss of perirenal and bone marrow fat. The visible omental, mesenteric and subcutaneous fat stores were depleted. Epicardial fat stores were not visibly affected.There was a high correlation between bone marrow crude fat and bone marrow dry matter (R=0.92). This suggests that dry matter estimations can be used to assess bone marrow fat stores. Perirenal fat may be intermediate in type between brown and white adipose tissue because it is mobilized in response to fasting, and formalin fixed perirenal fat did not contain detectable levels of thermogenin.