Selection And Identification Of Yeast Isolated From Ruminal Fluid And Study On Its Effect On Rumen Fermentation In Goats

Yeast,as an important microbial additive in livestock production,has a positive effect on the performance of ruminants.The objective of the thesis was to select and identity the yeast isolates from rumen liquid for use as a microbial additive in goats.In the present study,94 yeast isolates were got from rumen fluid of goats and cows.Based on the lactic acid-utilizing capacity and growth rates,1 isolates were selected to further investigate its influence on fermentation characterizes with different substrate;finally,we explored the effect of the yeasts on rumen fermentation in goats.In general,the present study consists of three parts.1 Selection and identification of yeast isolated from ruminal fluidThis experiment is proposed to select and identify the yeast isolates from rumen liquid.Ruminal fluid of goats and cows was used as bacteria source,and 94 isolates were obtained through the yeast selective medium.An isolate which growth rate is faster was isolated through the tests of lactic acid unitizing ability and growing curve determination.26S rDNA sequence analysis showed that the isolates was belong to Meyerozyma.The results showed that the types of yeast isolates are varied in the rumen.The lactic acid-utilizing ability and the growth rate of yeast isolates is also inconsistent,and some isolates presented a more fast growth speed and the good ability of lactic acid utilization.2 Effect of yeast strain Y09 on different substrate fermentation ability in in vitro fermentationThis study aims to study yeast strain Y09 on ruminal fermentation characteristics of three different feed substrate in vitro.The mixture of Chinese wildrye and concentrate,potato starch and corn starch were used as substrate,and the ruminal fluid from the dairy cattle was used as inoculant.The results showed that yeast addition decreased the ruminal pH and concentration of lactic acid(P<0.001)while increased the concentration of propionic acid and the digestibility of dry matter(P<0.05)with Chinese wildrye plus concentrate mixture as substrate.The addition of yeast decreased ruminal pH and lactic concentration(P<0.001)in the group of corn starch,moreover,the addition of yeast decreased the ruminal pH(P<0.05)and increased the concentration of propionic acid(P<0.05).However,the total gas production,and the concentrations of ammonia-N,acetic acid,butyric acid,isobutyric acid,valeric acid and isovaleric acid were not affected(P>0.05)by yeast addition in the three groups.The Real-time PCR data showed the isolate addition increased the number of total bacteria when Chinese wildrye plus concentrate and potato starch was used as substrate.Results indicate that the rumen yeast isolates can improve the rumen degradation capability of diet,reduce the content of lactic acid in Chinese wildrye plus concentrate and corn starch group,suggesting that the yeast isolates could improve the digestibility efficiency and may enhance the propionate production and the growth of ruminal bacteria.3 Effects of Y09 yeast isolate on rumen fermentation and the influence of feed digestibility in goatsThis study aimed to evaluate the effects of Y09 yeast on rumen fermentation,growth performance and feed efficiency in goats.The yeasts used in the present study were prepared using the solid fermentation method(living bacteria number is 5×108 CFU/g).14 goats were randomly divided into the two groups including control and treatment group.The result showed that,as compared with the control,the animal in treatment received 10 g yeast per day during the experiment.The results showed that,addition of yeast decreased lactic acid concentration and increased digestibility of crude protein in gastrointestinal tract(P<0.05),while did not affect the daily weight gain,feed intake,ration of feed to weight,pH,concentrations of NH3-N and TVFA,digestibility of organic matter,crude ether extract,neutral detergent fiber and acid detergent fiber and the ratio of acetate to propionate(P>0.05).The Real-time PCR data showed the yeast addition increased the number of total bacteria in rumen.Results indicate that yeast addition can stabilize ruminal pH,promote the growth of ruminal microorganism and digestibility of crude protein,however,it did not affect the growth performance of goat.