Studies With Purified Diets

CHICKS fed a purified diet containing increasing percentages of isolated soybean protein (Drackett), in increments of five percent over a range of 15 to 35 percent, grow at a progressively improved rate up to the 30 percent level, Snyder (1955). Similar observations have been reported by Pappenhagen et al. (1953). In Snyder’s experiments, subjecting the protein to various purification treatments failed to modify the pattern of growth. Snyder noted that in the presence of adequate protein (30%) the response from a mixture of crude sources of unidentified factors (5% alfalfa meal + 5% defatted liver powder + 5% whey) was 12 percent while for diets containing 25, 20 and 15 percent protein, the mixture of crude materials resulted in responses of 15, 18 and 29 percent, respectively. Thus, diets containing less than 30 percent protein appear to have benefited from the protein contributed by the crude sources of unidentified factors.