Urinary sulfur excretion and the nitrogen/sulfur balance ratio reveal nonprotein sulfur amino acid retention in piglets.
We evaluated the use of urinary sulfur (S) excretion as a measure of sulfur amino acid (SAA) catabolism and the nitrogen/sulfur (N/S) molar balance ratio as an indicator of nonprotein SAA storage in growing piglets. After confirming that an intravenous dose of sulfate is fully recovered in urinary sulfate, we measured urinary S recovery after an intravenous dose of methionine in 6 piglets fed an adequate protein (AP) diet and 6 piglets fed a low protein (LP) diet with normal energy provision. As measured over 48 h, recoveries of the methionine load as urinary total S was 106% in the AP group but only 69% in the LP group (P < 0.05). On the baseline diets the N/S balance ratio in the AP group was 36, whereas that in the LP group was 30 (P < 0.05); immediately after the methionine load, this ratio remained constant in the AP group but decreased further, to 26 (P < 0.05) in the LP group. These results indicate that protein-deficient piglets accumulate relatively more S than N from their diet, and under these conditions a significant portion of the S derived from a methionine load is retained in nonprotein compounds. Urinary S excretion, a simple nontracer measurement, can provide an accurate measure of SAA catabolism, and the N/S balance ratio is a potentially useful indicator of changes in nonprotein SAA stores of growing piglets.
Hou
Chunsheng
C
School of Dietetics and Human Nutrition, McGill University, Montreal, Quebec, Canada H9X 3V9.
Wykes
Linda J
LJ
Hoffer
L John
LJ
D000603:Amino Acids, Sulfur / Q000378:metabolism* / Q000493:pharmacokinetics; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake; D005978:Glutathione / Q000378:metabolism; D006710:Homocysteine / Q000097:blood; D008278:Magnesium Sulfate / Q000008:administration & dosage / Q000493:pharmacokinetics; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000097:blood; D009584:Nitrogen / Q000032:analysis*; D013455:Sulfur / Q000032:analysis* / Q000652:urine*; D013552:Swine; D013654:Taurine / Q000097:blood / Q000652:urine; D015430:Weight Gain
D000603:Amino Acids, Sulfur; D004044:Dietary Proteins; D006710:Homocysteine; D013654:Taurine; D013455:Sulfur; D008278:Magnesium Sulfate; D008715:Methionine; D005978:Glutathione; D009584:Nitrogen