Effects Of Inactivated Yeast Culture On Growth Performance,Rumen Fermentation And Immunity Of Lambs

This study was conducted to investigate the effects of inactivated yeast culture(IYC)supplementation on growth performance,apparent digestibility of nutrients,rumen fermentation,rumen microbial diversity,antioxidant performance,immunity,slaughtering performance and economic benefits on lambs.Eighty 3.5-month-old healthy crossbred male lambs(Dorper ×Hu)weighing 35.65±1.84 kg were selected and randomly divided into four groups,each group will consisted of 5 replications with 4 sheep per replication,lambs in CON,YCL,YCM,and YCH group were supplemented with 0g,5g,10g,and 15g of IYC per day to the basic diet.This experiment consisted of a 7-day adaptation period and a 60-day trial period.On the 40th day of the experiment,five sheep of similiar initial bodyweight were selected from each group for a digestive metabolism test.On the 60th day of the experiment,ten sheep were randomly selected from each group to collect rumen fluid and blood,then,pH,volatile fatty acids and microbiota in rumen fluid,as well as antioxidant and immune indicators in serum were measured.Five sheep were randomly selected from each group for slaughter test.The results showed that:1)With the increase of IYC,the final weight(P=0.056)and average daily gain(P=0.064)had a linear increasing trend,the dry matter intake gradually decreased and the difference was not significant(P>0.05),the feed/gain of YCH group was significantly lower than that of the CON(P<0.05).2)The digestibility of dry matter in YCL,YCM and YCH was significantly higher than that of CON group(P<0.05);the crude protein digestibility in YCH has significant increase compared to the group CON(P<0.05);the apparent digestibility of gross energy in YCL and YCH has a significant increase when compared with CON group(P<0.05).With the increase of IYC,the apparent digestibility of dry matter,crude protein and gross energy increased linearly(P<0.05),and the digestibility of neutral detergent fibers and Ca has a linear increase(P<0.05).3)With the increase of IYC level,the acetate concentration of rumen showed a quadratic increas(P<0.05).The concentrations of propionate and total volatile fat acids in YCH group were significantly higher than those in YCM group and CON group(P<0.05),and there were significant linear increase(P<0.05),the butyate showed a linear increase(P<0.05);acetate/propionate value,pH and molar ratio of individual volatile fatty acid did not differ significantly between groups(P>0.05).4)There was no significant difference in a diversity of the rumen bacterial community between groups(P>0.05);the differences in bacterial structure between group YCH and group CON were observed(P<0.05);the relative abundance of Bacteroidetes in phylum level of group YCH was higher when compared with group CON and YCL(P<0.05).The relative abundance of Fibrobacteres(P<0.05)in phylum level has a linear increase,as well as Ruminococcaceae(P<0.05)in genus level,with the increase of IYC.The relative abundance of Rikenellaceae(P<0.05)in genus level of group YCH and YCL was lower than that of group CON and YCM and Succiniciasticum in genus showed a linear increase trend(P=0.069).Through the correlation analysis between IYC and OTU,IYC has a negative regulatory effect on Veillonellaceae,Quinella and Treponema.5)The concentration of total antioxidant capacity in group YCH and YCL was higher when compared with group CON and YCM(P<0.05);the superoxide dismutase content in group YCL,YCM,YCH was higher than that in group CON(P<0.05)and has a linear increase(P<0.05);the malondialdehyde in group YCH was lower than that in group CON(P<0.05);IYC supplementation did not affect serum glutathione peroxidase(P>0.05).6)The content of immunoglobulins M?immunoglobulins G?immunoglobulins A in group YCH,YCM showed significant increase compared to group CON(P<0.05),and showed linear increase with the addition level of IYC.7)There was no significant difference in premortem living weight,carcass weight,dressing perccentage and gastrointestinal weight between groups(P>0.05).8)Compared with the CON group,the total feeding cost was 338.44 yuan each,the income of gain was 418.32 yuan each,the economic benefits of each sheep increased by 12.18%.In conclusion,IYC can change the rumen microbial community structure,promote rumen fermentation,improve the antioxidant performance and immune performance and apparent digestibility of dry matter,crude protein,gross energy of fattening lambs,then improve growth perfomance,and there is a dose dependence observed.