Abstract: China′s beer production produces a large number of by-products every year, such as spent grains and waste yeast. Furthermore, the slaughtering industry also produces a great number of livestock blood by-products. Both of them have high nutritional value and are suitable for use as raw materials for production of fermented feed. This study developed a production process for fermented protein feed using spent grains and dried blood as main and auxiliary materials, respectively, in combination with inoculating different probiotics. To determine the optimal production conditions, the protein content, sugar content and total acid content of the fermentation products were assessed, and the impacts of different ratios of main and auxiliary ingredients, fermentation time, and inoculation methods and inoculum size of yeast and lactic acid bacteria on the quality of mixed fermented feed were evaluated. The results showed that fermentation products with good quality were obtained under the following conditions the addition amount of dried blood （auxiliary material） was 15.00%, fermentation temperature was 30 ℃, inoculating strain was yeast with amount of 2.00%, and fermentation time was 5 days. The protein content of the fermentation products reached up to 50.36% which was elevated by 75.53% compared to that of the initial samples. When yeast and lactic acid bacteria were used to produce mixed fermentation feed, the 1.00% of lactic acid bacteria were inoculated first and fermented for 2 days, and then the 1.00% of yeast was added to continue fermentation until 7^th day.Under this condition, the protein content of the mixed fermentation products reached up to 59.27% which was elevated by 106.59% compared to that of the initial samples. It can be concluded that the fermentation products obtained by the above two methods can serve as good protein feed.

Key words: spent grains, dried blood, probiotics, protein feed