J. Anim Sci.
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J. Anim Sci. 1980. 51:1011-1022.
© 1980 American Society of Animal Science
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Energy and Protein Metabolism in Ewes as Influenced by Age and Dietary Protein-Calorie Ratio

J. M. Koenig, J. A. Boling and L. S. Bull1

University of Kentucky,2 ,3,, Lexington 40546

Abstract

A 2 x 2 x 2 factorial design of treatments was used to study effects of age (20 months or 10 years), dietary energy density (3.0 or 3.5 kcal DE/g) and protein level (8 or 16% crude protein) on energy and nitrogen metabolism in two groups of ewes, with emphasis on efficiency of metabolizable energy utilization. Plasma glucose concentrations were the same for sheep in each age group, regardless of diet; plasma lactate was higher (P<.03) in plasma of old ewes and decreased (P<.01) in concentration when dietary energy density was increased. Plasma urea nitrogen was higher (P<.0001) in ewes fed diets containing 16 vs 8% protein, and plasma ammonia concentrations were higher (P<.02) in old ewes. Dietary energy and protein levels affected digestible and metabolizable energy, but no age-related effects were observed. Nitrogen retention was increased when either energy (P<.0001) or protein (P<.003) intake increased. Oxygen consumption was the same for sheep of either age (expressed per kilogram metabolic body weight), while estimated maintenance requirement and heat production were higher for old ewes. Metabolizable energy utilization was lower (P<.05) in old ewes fed the lower energy density diets than in those fed higher energy diets. Increasing dietary energy density increased (P<.05) efficiency of metabolizable energy utilization in old ewes to a level comparable to that observed in young ewes.

Footnotes

1 Present address: Dept. of Anim. and Vet. Sci., Univ. of Maine, Orono, 04473.

2 Dept. of Anim. Sci.

3 This paper (No. 79-5-179) is published with the approval of the Director of the Kentucky Agr. Exp. Sta.






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Copyright © 1980 by the American Society of Animal Science.