Growth-Promoting Effects of Fermented Soybeans for Broilers

Four factorial experiments are here reported on the use of control and fermented soybeans in glucose-soybean diets for broiler chicks with varying protein levels (15, 17 and 19% and 13, 16 and 19%). Eleven strains of Aspergilli were used as cultures in these experiments, selected on the basis of a prior history of beneficial effects. Data obtained from 4-week growth studies revealed that feeding soybeans fermented with 10 of the 11 species gave significant (P < 0.05) improvements in weight gain and feed efficiency. The responses were more pronounced with the low dietary levels of protein. No detrimental effect was shown from any of the cultures tested. Chemical analyses indicate that chicks fed the fermented soybean diets made better use of dietary nitrogen and dry matter. Carcass composition data show that the diets made with fermented soybeans produced chicks that were significantly (P < 0.05) higher in protein and ash and lower in total lipids. Amino acid analyses suggest that the growth-promoting activity was largely due to a greater supply of the essential amino acids. Some vitamin synthesis by the fungi is a possibility.