ORIGINAL PAPER
Studies on N-metabolism in different gastrointestinal sections of sheep using the digesta exchange technique. 4. Whole body protein metabolism
A. Sandek 1,   K. Krawielitzki 2,   J. Kowalczyk 3,   M. Gabel 1,   T. Żebrowska 3,   F. Kreienbring 2,   H. Hagemeister 4,   J. Voigt 4  
 
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1
Institute for Ecologically-Compatible Animal Husbandry, University of Rostock, Justus-von-Liebig-Weg 8, 18059 Rostock, Germany
2
Institute for Applied Agroecology, Justus-von-Liebig Weg 8,18059 Rostock, Germany
3
The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, 05-110 Jabłonna, Poland
4
Research Institute for the Biology of Farm Animals, Research Unit Nutritional Physiology “Oskar Kellner”, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany
CORRESPONDING AUTHOR
J. Voigt   

Research Institute for the Biology of Farm Animals, Research Unit Nutritional Physiology “Oskar Kellner”, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany
Publication date: 2002-10-11
 
J. Anim. Feed Sci. 2002;11(4):589–599
 
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ABSTRACT
Parameters of protein turnover were measured in sheep differing in postruminal secretion and reabsorption of nitrogen. The experiments were carried out with Polish Merino sheep (20-25 kg BW) fitted with rumen and re-entrant cannulas at the duodenum and the ileum. Two groups of animals (n=9) were fed with diets that were nearly isonitrogenous but differed in crude fibre (CF) content (CF in % dry matter (DM): Group 1, 14.7, Group 2, 24.9). As a result of the higher CF content, the intake of DM was lower in Group 2 than in Group 1 (616 vs 467 g x d-1). In all carried out experiments (Sandek et al., 2001a) one of the three animals (No 1) was labelled with 15N by intraruminal infusion of 15N urea. Then duodenal digesta of this labelled animal was exchanged with digesta of an unlabelled animal (No 2) during a 48 h period. The N- and 15N flow through the intestinal tract, the N and 15N excretion in faeces and urine as well as the absorption rates were estimated in animal No 2 during that period. Using these data, kinetic parameters of protein turnover were calculated using the end-product method and the 3-compartment model. Intake of N (16.1 vs 11.7 g x d-1 in Groups 1 and 2), net N absorption (12.3 vs 7.3 g x d-1) and N balance (104 vs -56 mg x kg BW-1 x d-1) were higher in Group 1 (P<0.10). No difference were found in flux (1666 vs 1458 mg N x kg BW-1 x d-1), synthesis (1238 vs 1087 mg N x kg BW-1x d-1) or breakdown (1134 vs 1324 mg N x kg BW-1 x d-1) of protein. However, the efficiency of protein synthesis (N balance/synthesis x 100) was significantly higher in Group 1 (8.8 vs -5.2%) (P<0.10). The efficiency of protein synthesis correlated negatively with N secretion in the postruminal tract (r =-0.99; P<0.001) and with ileal flow of endogenous N (r =-0.95; P<0.01). In conclusion, a high intestinal N secretion adversely affects the efficiency of whole body protein synthesis in growing sheep.
ISSN:1230-1388