THE EFFECT OF A HIGH-DOSE OF 3-HYDROXY-3-METHYLBUTYRATE ON PROTEIN-METABOLISM IN GROWING LAMBS

The effect of a high dose of 3-hydroxy-3-methylbutyrate (HMB, a leucin e catabolite) on protein metabolism was investigated in growing male l ambs fed on hay and concentrate. Concentrate was supplemented with eit her Ca(HMB)(2) (4 g/kg) or Ca(CO3)(2) in experimental (HMB) and contro l groups respectively. Both groups consisted of six 2-month old lambs. Three complementary methods to study protein metabolism were carried out consecutively 2.5 months after beginning the dietary treatment: wh ole body phenylalanine fluxes, postprandial plasma free amino acid tim e course and fractional rates of protein synthesis in skeletal muscles . Feeding a high dose of HMB led to a significant increase in some pla sma free amino acids compared with controls. Total, oxidative and non- oxidative phenylalanine fluxes were not modified by dietary HMB supple mentation. Similarly, an acute infusion of HMB, in the control group, did not change these fluxes. In skeletal muscles, fractional rates of protein synthesis were not affected by long-term dietary supplementati on with HMB. Taken together our results showed that administration of a high dose of HMB to lambs was able to modify plasma free amino acid pattern without any effect on whole-body protein turnover and skeletal muscle protein synthesis.