Improvement of Nitrogen Utilization with Manipulation of Urea Recycling in Beef Cattle-Effect of weaning on urea metabolism in calves-
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Accession number;05A1044281
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| Title;Improvement of Nitrogen Utilization with Manipulation of Urea Recycling in Beef Cattle-Effect of weaning on urea metabolism in calves- |
| Author;
OBITSU TAKETO
(Hiroshima Univ., Graduate School of Biosphere Sci., JPN)
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Journal Title;Shokuniku ni kansuru Josei Kenkyu Chosa Seika Hokokusho
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Journal Code:X0296A
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ISSN:
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VOL.23;NO.;PAGE.154-158(2005)
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| Figure&Table&Reference;TBL.2, REF.9 |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;Six calves were used to investigate the effect of weaning on urea metabolism including production, gut entry and subsequent fate of urea-N. Three calves (W group) were fed a milk replacer, concentrate and hay until 7 weeks of age, then they were given only the solid feeds. Another three calves (MF group) were fed a milk replacer, concentrate and hay until 13 weeks of age, then they were given same diets as W group. From 7 weeks of age, calves in both groups were fed isocaloric and isonitrogenous diets to support a growth rate of 0.9 kg/d. At 12 and 18 weeks of age, urea kinetics were measured by isotopomer analysis with '15'N labeled urea. Urea synthesis rate (UER) and gastrointestinal entry rate (GER) per metabolic body size (MBS) for MF calves were lower than W calves at 12 weeks of age, but they increased at 18 weeks of age. The proportion of GER to UER for W calves was higher at 12 weeks of age, but there was no difference between MF and W calves at 18 weeks. The proportion of re-synthesis of urea-N to GER was similar between MF and W calves across the ages. As a result, anabolic use of urea-N per MBS for MF calves increased from 12 to 18 weeks of age. These results indicate that the contribution of recycled urea-N to N use in calves increases with weaning. (author abst.) |
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