Eitam, H., Institute of Animal Science, Department of Ruminant Science, Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel, Department of Evolutionary and Environmental Biology, Faculty of Science and Science Education, University of Haifa, 31905 Haifa, Israel
Agmon, R., Institute of Animal Science, Department of Ruminant Science, Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel
Asher, A., Institute of Animal Science, Department of Ruminant Science, Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel
Brosh, A., Institute of Animal Science, Department of Ruminant Science, Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel
Orlov, A., Institute of Animal Science, Department of Ruminant Science, Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel
Izhaki, I., Department of Evolutionary and Environmental Biology, Faculty of Science and Science Education, University of Haifa, 31905 Haifa, Israel
Shabtay, A., Institute of Animal Science, Department of Ruminant Science, Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Israel

For ruminants, dietary protein is the first limiting component to the utilization of low-quality forage. Throughout gestation, low-protein intake may result in prenatal programming that causes various metabolic disturbances and physiological modulations to dams and their developing embryos. We studied the effect of long-term low-protein diet (LPD) on physiological, biochemical, and molecular parameters of the energy status in gestating beef cows. LPD resulted in significant reductions in feed intake and heart rate and promoted a negative retained energy status already after 3 weeks. Elevated levels of plasma creatinine and non-esterified fatty acids indicate endogenous degradation of fat and protein as a response to the demands in energy and nitrogen. Increasing levels of â- hydroxybutyrate confirmed the negative energy status obtained by the physiological measurements. At the molecular level, subcutaneous fat, Hsp90, Hsp70, and proteasome subunits decreased significantly after 3 months on LPD, in parallel with an increase of adipocyte fatty acidbinding protein. These results may indicate a decrease in turn-over of proteins, at the cost of induced lipolysis, and suggest that the response to protein deprivation, when examined in an energy-storing tissue, includes downregulation of the constitutive heat shock proteins involved in the protein degradation pathway of energy production and upregulation of tissue-specific genes such as those involved in energy production from fat degradation. © 2011 Cell Stress Society International.