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Dietary Requirements for Fertility and Lactation

XXVIII. The Lactation-Promoting Properties of Cystine When Added to Casein Diets¹

Department of Agricultural Chemistry, University of Arkansas, Fayetteville

The purpose of this investigation was to determine the lactation-promoting properties of various fats and oils, such as lard, butterfat, hydrogenated cottonseed oil, olive oil, and wheat germ oil in combination with hydrogenated cottonseed oil, fed at a 15% level on two types of salt mixtures. The rations contained 17.7% purified casein and 3.7% protein derived from the dehydrated bakers' yeast used as a source of the vitamin B complex. The albino rats used in this study were started on the experiments soon after weaning at initial weights ranging from 60 to 80 gm.

Regardless of the nature of the fats or oils, or the composition of the salt mixture, such diets did not meet the demands of lactation. The limiting factor in the rations was found to be cystine. When the rations were fortified with 0.2% cystine, or daily administration of 20 to 40 mg. cystine to the lactating mothers was begun as failure of lactation became evident, lactation proceeded successfully and the young were weaned.

The results of this study do not necessarily prove the essential nature of cystine, but do show that the lactation-promoting properties of a diet containing about 18% casein are markedly improved by the addition of this amino acid. Since casein contains 3.0 to 3.3% methionine, the rations provided about 0.6% of this amino acid, but apparently this amount is insufficient for rearing of young and supplementary cystine can meet the need for successful lactation.

Manuscript received 14 June 1941.