Further observations on the cystine deficiency of lucerne proteins and the effect of heat and incubation upon their growth-promoting value

Abstract

Lucerne is not only high in minerals and vitamins but also in proteins, yet, curiously enough, it is rather low in cysteine as determined biologically with rats by Haag (1931). This discovery may be of importance to parts of this and other countries where some domestic animals are, for certain seasons of the year, almost solely subsistent on the Lucerne plant. However, it is dangerous to reason by analogy from one species to another, and it cannot be inferred, therefore, that Lucerne is low in cysteine for animals such as, for instance, sheep and cattle, in view of the great anatomical and physiological differences in their digestive systems. Furthermore, even though Lucerne is low in cysteine, the large capacity of ruminants for food may make it possible for them to obtain enough of this essential amino-acid to promote normal growth and production. Another probability is that sheep may be capable of synthesizing cysteine through a special function of their wool follicles as suggested by Fraser and Roberts (1932), or through a symbiotic action of their intestinal flora and fauna (bacteria, protozoa, etc.), as postulated by Rimington and others (1932, 1933). The latter hypothesis has given impetus to studies in this field, and the preliminary experiments, to be presented in this paper, have been carried out with the object of seeing whether Haag’s results could be substantiated and what the effect of heat and incubation with a sheep’s “ruminal juice” would be upon the utilization of Lucerne-meal proteins by the rat. Furthermore, because maize, Lucerne and teff (Eragrostis Abyssinica) form three of the major food materials for animals in this country, it was thought of interest to study also the supplementary values of maize-lucerne and maize-teff proteins.