Methionine, Choline and Threonine Interrelationships for Growth and Lipotropic Action in the Baby Pig and Rat

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Abstract
Experiments were designed to study the response of the baby pig (weaned at 3 weeks) to dietary choline, methionine and threonine level and to examine the relationships among these factors for growth and lipotropic action in the weanling rat. In both species, a gain response to supplemental choline was obtained when dietary methionine was insufficient. A level of methionine only slightly above that required for maximal gain completely eliminated the need for dietary choline in preventing liver fat accumulation in rats. Isolated soybean protein diets containing 0.31 % methionine, 0.10% cystine and 1646 mg. of choline per kg. of diet supported performance in pigs equal to that obtained with similar diets containing 0.42% methionine, 0.10% cystine and no choline. Soybean meal diets unsupplemented with choline provided sufficient choline (600 mg./kg.) to partially, but not completely, prevent accumulation of excessive liver fat levels in rats (9.2 vs. 16.0% for supplemented and control groups, respectively). Supplemental threonine improved performance of pigs and rats fed isolated soybean protein at a level of 12% protein when methionine content reached 0.42%. Liver fat of rats was increased slightly with supplemental threonine in the absence of choline. This was interpreted to mean that the addition of threonine, the second-limiting amino acid in soybean protein, resulted in greater tissue protein synthesis, and less methionine was available for lipotropic action. Rats fed diets containing isolated soybean protein without supplemental methionine or choline had livers which contained 42% fat on a dry weight basis as compared to values of approximately 11% in the presence of 1646 mg. of choline per kg. of diet or of 0.42% methionine. Copyright © 1967. American Society of Animal Science . Copyright 1967 by American Society of Animal Science