Ruminant Nitrogen Usage (1985) / Chapter Skim
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9 Nitrogen Metabolism in Tissues
9 Nitrogen Metabolism in Tissues
Pages 57-65
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From page 57... ...
Free Amino Acid Pools Most of the amino acids in the body are bound by peptide bonds in proteins. A small portion of the amino acicis are free and equilibrate in pools.
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From page 58... ...
temporarily reflected in the free amino acid pools of plasma after feeding diets that result in large excesses or deficiencies of amino acids passing into the duodenum (Bergen, 1979~. Frequently, there is no postprandial rise in plasma amino acids in functional ruminants (Theurer et al., 1966; Fenderson and Bergen, 1972~.
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From page 59... ...
Although large quantities of amino acids pass through the free amino acid pools, there is limited storage of free amino acids in the body, and consequently the free amino acid pools do not represent a reserve of amino acids for protein synthesis. Most of the amino acids are bound in proteins and excess amounts of amino acids are oxidized.
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From page 60... ...
Increasing amino acid intake above requirement increases oxidation. Available evidence suggests that excesses of EAA, due to high absorption from the GIT or by a relative excess due to a scarcity of one or more amino acids, are removed from the free amino acid pools by oxidation in the liver.
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From page 61... ...
PROTEIN REQUIREMENTS The amino acid requirements of ruminants could be estimated by summing the net removal of free amino acids from the free amino acid pools (Figure 12~. Practically, this is not possible because all losses have not been quantitaterl.
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From page 62... ...
Creatine, urea, ammonia, allantoin, uric acid, hippuric acid, and small quantities of amino acids contribute to UPN. UPN is difficult to estimate in ruminants because there is some absorption of amino acids when they are fed nitrogen-free diets as a result of microbial growth originating from nitrogen recycled into the rumen.
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From page 63... ...
and 160 (NRC, 1978~. Protein content of empty body weight changes in adult ewes ranged from SO to 70 g protein/kg EBW in a study by Rattray et al.
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From page 64... ...
, and for producers who usually know the fat content of milk, but not true protein, it would possible to estimate protein content from fat content (NRC, 1978~. It is recognized that there is considerable variation in protein content of the products of animal production due to genetics, rate of production, and nutritional his TABLE 19 Protein Retention in Fetus and Gravid Uterus of Cattle at Different Stages of Gestation Age (Week from Conception)
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From page 65... ...
The two major pathways of amino acid metabolism are protein synthesis or oxidation (Figure 13~. Efficiency of transfer of amino acids into product protein can then be calculated from: (Amino acids in product)
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