Factors associated with utilization of the calcium salt of methionine hydroxy analogue by the young chick.

Six growth assays were conducted using crystalline amino acid diets to investigate the efficacy of methionine hydroxy analogue (OH-M) as a precursor of sulfur bearing amino acids (SAA). The influence on OH-M utilization of dietary modifications of the methionine-cystine ratio, inorganic sulfate as K2SO4 and supplemental mixtures of the branched-chain amino acids (leucine, isoleucine and valine) was explored. Performance of chicks fed OH-M was inferior to those fed an equivalent molar quantity of DL-methionine. Additional dietary sulfate or supplemental mixtures of the branched-chain amino acids did not improve OH-M utilization. OH-M was found to support growth equal to that of 0.35% methionine and 0.35% cystine when fed at a level 25% above the SAA level provided by methionine and cystine. On a weight basis the calcium salt of OH-M has 88.15% OH-M activity. From assays reported herein the calcium salt of OH-M was calculated to have approximately 70% methionine activity.