Effects Of Active Dry Yeasts On Performance,Rumen Fermentation And Methane Production Of Lactating Dairy Cows

This experiment was conducted to evaluate the effects of dietary active dry yeast supplementation level on performance,rumen fermentation and methane production of lactating dairy cows.Sixty Chinese Holstein dairy cows with similar lactation days,parity,daily average milk yield and body weight were selected and divided into groups I,II,III,and IV with 15 replicates in each group and 1 cow in each replicate according to the principle of random distribution.The dairy cows were fed with same the basal diet,and the groups I,II,III,and IV were added with 0 g,10 g,20 g and 30 g active dry yeast per head each day,respectively.The feeding trail period was 90 day.The results showed that: 1)There was no difference in dry matter intake and feed conversion among the experimental groups(P>0.05).The milk yield of group III was significantly increased by 4.09%(P<0.05)compared to group I.Compared with the group I,the 4% fat corrected milk of group III and IV was significantly increased by 8.48%(P<0.01)and 7.32%(P<0.05),respectively.2)Compared with group I,the nutrient apparent digestibility of crude protein in group II and III was significantly increased by 6.93% and 7.22%(P<0.05),respectively.The nutrient apparent digestibility of acid detergent fiber in group II,III was significantly increased by 13.95% and 13.26%(P<0.05)compared to group I,respectively.3)Compared with group I,serum urine nitrogen in group II,III and IV was significantly reduced by 21.82%,21.44% and 21.06%(P<0.05).Compared with group I,non-esterified fatty acids in group II,III and IV was significantly reduced by 9.34%,10.09% and 9.36%(P<0.05).4)Compared with group I,microbial protein in group II,III and IV was significantly increased by 26.87%,29.85% and 24.63%,respectively(P<0.05).Compared with the group I,the acetic acid and total volatile fatty acid in the rumen of group III was significantly increased by 5.87% and13.59%(P<0.05),respectively.5)Compared with group I,methane production in group II,III and IV was significantly reduced by 7.91%(P<0.05),16.99%(P<0.01)and 10.66%(P<0.05).6)The abundance of Fibrobacteres in group IV was significant higher than that in group II and III(P<0.05).Compared with group I,the abundance of Firmicutes in group III was increased(P<0.01).The abundance of Fibrobacteres in group II was significant higher than that in group I(P<0.05),however,the abundance of Tenericutes in group II was significant reduced than that in group I(P<0.05).Compared with group I,the abundance of Shuttleworthia in group IV was increased(P<0.05).7)Compared with group I,group II and III reduced the abundance of Methanobrevibacter and Methanosaeta(P<0.05).Through the Unweighted Unifrac principal coordinate analysis(PCoA),the contribution rates of the horizontal component and the vertical coordinates component were 20.80% and 17.79%,respectively.The rumen archaea flora of the active dry yeast group showed obviously clustering,and the communities differences were significant in each group(P<0.01).In conclusion,under the conditions of this experiment,active dry yeast can improve the performance,promoting rumen fermentation and reduce methane emissions.The appropriate amount of active dry yeas is 20 g/d/head.