Delayed excretion of 3-methylhistidine in goats

Quantitation of urinary 3-methylhistidine excretion in growing dogs as an index of in vivo skeletal muscle catabolism

Purpose: To quantitate urinary 3-methylhistidine (3-mh) excretion as an index of in vivo muscle catabolism in dogs fed diets containing either normal or high protein levels.Methods: Twelve male, 5-month-old Beagle dogs were housed individually in metabolism cages and fed a non-meat, purified diet. They were divided into two diet groups of six dogs each, receiving 22.6% (NP) or 41.1% (HP) DM crude protein, respectively. Three dogs from each group received an intravenous injection of 385 +/- 29 kBq [14C] 3-mh. HCl. Urine and feces were collected daily until radioactivity returned to background levels (17 days). Urinary 3-mh was measured using an amino acid analyzer and percentage of bound 3-mh was estimated via acid hydrolysis.Results: Results are reported as means +/- SEM. 3-mh recovery in urine and feces of dogs were 263 +/- 28 kBq and 50.7 +/- 2.2 kBq and 327 +/- 45 kBq and 25.9 +/- 25.9 kBq for the NP and HP groups, respectively. The total cumulative 3-mh recoveries for the NP and HP groups were 81.8% +/- 2.8 and 91.4% +/- 2.7, respectively. Bound 3-mh accounted for 2.1 to 4.8% of urinary 14C-3-mh.Conclusions: Growing Beagle dogs excrete a higher percentage of 3-mh in feces (13.5% vs. 6.7%) when consuming the NP versus the HP diet. It appears that some of the 14C was lost in CO(2) and/or re-circulated in the body, as reported for sheep and pigs. We conclude that urinary 3-mh does not appear to be a quantitative index of in vivo muscle catabolism in growing dogs.

Response of renal orotic acid and creatinine to treatments affecting metabolic protein supply of ruminants

90 urine samples obtained in three lamb trials and one experiment using adult wethers were analyzed for their contents of orotic acid and creatinine. The average daily excretion of orotic acid accounted for 0.5 mg to 1.5 mg (35 micrograms to 130 micrograms/W0.75) with a high individual variation. Correlation coefficients between orotic acid and other urinary constituents were low indicating an entirely different response to metabolic variations. There was only a weak relationship to live weight, protein retention and rumen fluid traits. Defaunation reduced the orotic acid excretion (significant in the adult wethers) whereas the addition of rumen-protected lysine as well as the use of different dietary carbohydrate sources were without effect. The urinary excretion of creatinine increased with live weight and age from 0.4 g/d in the 20 kg lambs to 1.7 g/d in the adult 53 kg wethers. The correlations with live weight were close whereas the apparently negative correlation with protein retention was not real as could be evaluated by calculation of the partial correlations. There was a close correlation of creatinine with total N, urea and allantoin. Neither defaunation nor rumen-protected lysine and the kind of carbohydrate source had significant effects on creatinine. The use of orotic acid and creatinine as indicators of metabolic disorders were discussed. Easy application in practical diagnosis without quantitative urine collection might be possible by the determination of orotic acid in the milk of cows and of the creatinine/N ratio in urine.