Nt-methyl histidine excretion by poultry: not all species excrete Nt-methyl histidine quantitatively

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Abstract
1. The rate of elimination of administeredNτ-[14CH3]methyl histidine was used to assess the validity ofNτ-methyl histidine excretion as an index of muscle protein breakdown in poultry.2. Broiler chicks (2–3 and 4–5 weeks old), laying hens, adult quail (Coturnix coturnix japonica), adult cockerels and turkey poults (2–4 weeks old) were tested.3. All except the turkey poults showed quantitative recoveries ofNτ-[14CH3]methyl histidine within 1 week.4. Turkeys showed a different pattern ofNτ-[14CH3]methyl histidine output; the mean total recovery after 14 d was less than 50% of the injected dose. The majority of the label remaining after this time was found in breast muscle.5. All birds tested excretedNτ-methyl histidine unchanged, although a small amount sometimes appeared as another metabolite.6. No significant oxidation ofNτ-[14CH3]methyl histidine by broiler chicks, turkey poults or adult quail was found.7. The results show that excretion ofNτ-methyl histidine is a useful measure of muscle protein breakdown in the domestic fowl and quail but not in turkeys.