The Study And Application Of Feed Active Dry Yeast

For a long time , antibiotics was added into animal feed as the growth-promoting additive, However, it leads to more and more threat on human safety because of the drug remanet and drug-fast of bacteria. Thus, to find a kind of new and safe growth-promoting additive has become to be a realistic demand. At present, research in-country and overseas is focused on the field of probiotics, prebiotics, immune-enhancer, herbal medicine and enzymes. This study develops a product of live yeast, which belongs to probiotics. By means of the lab work, we select one strain of yeast, which grows fast and produceslow Carbon dioxide. According to the results of identification this strain is determined to be a Saccharomyces cerevisiae, which is from the strain library of Angel Yeast Company. After studying some basic characteristic of this strain, we carry out a lot of fermentation experiment and finally found out a good procedure which is suitable for lab fermentation. In addition, according to this lab procedure, we designed techniques to do trial-produce, and got one batch of yeast product. With this yeast product, we did some animal-trial to get the application method and the dosage. The result reveals that this yeast can increase growth speed of weanling-piglet. Besides, it can also improve reproductive performance and reduce the intestinal constipation rate of gestation sow.In the first part of this study, we selected and identified the feed yeast strain. Comparing the ability of growth speed and CO₂ output, we selected the strain. According to Lodder yeast classify handbook, the strain belongs to S. cerevisiae.In the second part, we studied the fermentation capability of this feed yeast. The results reveals: the strain has no hypha and the death temperature is 58℃in malt wort. It can live in 38°C on malt wort solid culture, and it can resist 12% ethanol and 10% NaCl.In the third part, we carried out a lot of fermentation experiment and finally found out lab fermentation procedure and production techniques. We also studied carbon source, nitrogen source, air flow, agitation and pH. Finally we found that the concentration of fermentation for yeast is able to reach 180 g/L wet weight of yeast, 20 billion live yeast per gram dry yeast and the live rate is more the 80%, which proves that the strain can be suitable for large-scale production well.At last, we did some application research in swine. We did animal-trial to get the application method and the dosage. The result reveals that this yeast can increase growth speed of weanling-piglet. It can also improve reproductive performance and reduce the intestinal constipation rate of gestation sow. In the diet of weanling-piglet and gestation sow, the dosage of 1000 gram/ton is better. To reduce the intestinal constipation rate ,the dosage should be 600 gram/ton.