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Maternal Energy Status and Development of Liver and Muscle in the Bovine Fetus¹

U.S. Department of Agriculture^,3, Clay Center, NE 68933

Abstract

The effects of daily metabolizable energy intakes of 9.5 (low), 15.4 (medium) and 24.9 (high) Meal in pregnant yearling heifers on maternal serum metabolite concentrations and on fetal development as indicated by RNA, DNA and protein concentrations in liver and semitendinosus muscle were studied in 88 crossbred heifers. Pregnant heifers were slaughtered at 90, 120, 150, 180, 210, 240 and 255 days of gestation. Average daily gains (kg) were .14, .58 and .95 and fetus, fluids and membranes accounted for 100%, 27% and 16% of the total live weight gain of the heifers fed the low, medium and high energy diets. Maternal serum free fatty acids (FFA) were not altered (P>.05) by maternal energy level. Glucose concentrations were highest (P<.025) and urea-N concentrations lowest (P<.025) in heifers fed high energy compared to low energy levels. Maternal liver DNA concentrations (mg/g tissue) were higher (P<.025) and the protein/ DNA ratio lower (P<.025) in the low energy diet compared to the medium or high energy diets. Concentrations of liver RNA and protein were not influenced (P>.10) in maternal liver by level of energy intake. Fetal liver and muscle RNA and DNA concentrations decreased (P<.05) with increasing gestational age. Fetal muscle protein increased (P<.05) and liver protein did not change with increasing gestational age. The only indications of an effect of dietary energy intake on fetal development were in fetal liver RNA concentrations which were increased and in the protein/RNA ratio in muscle which was decreased in fetuses from heifers fed low energy compared to the high level of energy intake.

It is concluded from these studies that restriction of energy intake in the bovine female to a level that maintains maternal body weight has little influence on the development of the fetus even though maternal metabolism may be altered considerably by level of energy intake.

¹ Cooperation of the Nebraska Agricultural Experiment Station, University of Nebraska, Lincoln, is acknowledged. The authors gratefully acknowledge the assistance of Mr. D. Mitchell in the care of the experimental animals, the excellent laboratory assistance of Ms. I. Jackson, Ms. J. Jacobson, Ms. S. Rothfuss and Mr. R. Mlejnek and the secretarial assistance of Ms. M. Stones in the preparation of this manuscript.

² Present address: USDA-SEA, Richard B. Russell Agricultural Research Center, Athens, GA 30604.

³ Roman L. Hruska U.S. Meat Animal Research Center, Agricultural Research, Science and Education Administration. Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.