Japan’s low rate of food self-sufficiency—particularly in terms of its livestock industry—is a cause for concern. In addition, Japan annually generates food waste equivalent to 20% of the food consumed. Many producers of natto—a fermented soybean product with high nutritional benefits—face difficulties in disposing of expired products or surplus stock. To address these issues of food self-sufficiency and food waste disposal, we have been exploring the possibility of adapting unused natto as a feed for swine and poultry. Here, we prepared dried natto (DN) from commercial expired natto and investigated its suitability as a feed supplement for layer chickens.
In preliminary studies, we confirmed that feed supplemented with 3% DN had adequate palatability for feeding to chickens. This study revealed that the egg productivity and feed conversion efficiency of chickens that received fed the diet with 3% DN did not differ significantly from those of a control group. In addition, DN supplementation did not affect various measures of egg quality, including shell strength and freshness, or alter the concentrations of isoflavones and vitamin E in eggs. However, yolk concentrations of vitamin K and cholesterol decreased after supplementation with DN; the water-insoluble fraction of DN caused the decrease in cholesterol. These results suggest that expired natto can be used as a feed supplement with decent effects on egg quality. Further study is needed to evaluate the reusability of various food wastes to build a worldwide food-recycling society.