The choline-methionine interrelationship for growth of the chick

Three experiments involving 1230 battery-reared crossbred chicks were conducted to evaluate the potential sparing effect of choline on methionine and vice versa. Experiment 1 employed a crystalline amino acid diet to establish the sulfur-amino acid (SAA) and choline requirement for maximal feed efficiency of chicks during the period 8 to 18 days posthatching. Six graded levels of DL-methionine (.20 to .45% in the presence of .20% L-cystine) and five of choline (0 to 1216 mg/kg) were employed in a 6 X 5 factorial treatment arrangement. Gain/feed ratio was maximized at 608 mg/kg choline at all levels of methionine and at .30 to .35% methionine at all levels of choline. Two identical experiments (8 to 25 days posthatching) with a corn-soybean meal diet were carried out to explore the relationship between supplemental methionine (0 to .20% in five equal increments) and supplemental choline (0, 217, and 434 mg/kg). Optimal performance occurred at .10% supplemental methionine regardless of choline level and at 217 mg/kg choline at supplemental methionine levels of 0 and .05%. At .10, .15, and .20% supplemental methionine, no gain or gain/feed response to supplemental choline was observed. It was thus apparent that excess levels of choline had minimal capacity to reduce the dietary requirement for methionine. Excess levels of methionine, however, seemed to have a consistent, although small, effect on the chick's dietary need for choline.