A Primary Research On The Nutrient Digestibility Of Protein-rich Yeast Products Used As Pig Feed

The aim of this paper was to evaluate the effect of different protein-rich yeast products on the growth performance of pigs,and the digestibility of gross nutrients,cell wall polysaccharides(NSP)and amino acids(AA)at different segements of the pig digestive tract.The dry beer yeast,yeast autolyzed powder and micro-ground dry yeast were used as sole protein source to prepare 3 tested diets,i.e.,dry beer yeast diet(DBY),yeast autolyzed diet(YAD)and micro-ground yeast diet(MYD),respectively,in this experiment.Six male castrated crossbreed(Duroc×Landracex Large white)growing pigs with an average initial body weight of 30.1kg±2kg were selected and fit a T-cannulate at distal ileum simultaneously.The 3 tested diets were allotted to 6 pigs according to a 3x3 Latin square design with 2 pigs for every tested diet in each period.A total of 3 periods was carried out.Each period lasted for 10 days,including the first 5 days of adaption period and 5 days of formal trial period during which the feces and ileal samples were collected.The main results of the experiment were as follows:Experiment 1.The Nutrient Digestibility of Protein-rich Yeast Products Used as Pig FeedThe aim of this experiment was to evaluate the difference in the apparent nutrient digestibility of 3 yeast products used as pig feed.The results showed that MYD revealed a higher coefficient of apparent digestibility of OM(P=0.043)in the total digestive tract(TDT)than those of DBY,YAD showed a higher coefficient of apparent digestibility of CP(P=0.021)than those of DBY in the terminal ileum(TIT),MYD showed a less higher coefficient of apparent digestibility of most of nutrients than those of DBY and YAD in the TIT and TDT,MYD showed a higher coefficient of degradation of Ca(P-0.006)than those of DBY and YAD in the TIT.Different yeast source diets have a significant influence on degradation of other mineral elements,such as Mn(P=0.027),Fe(P=0.037)in TIT and Mg(P=0.005),Zn(P=0.027)in TDT.The results showed that DBY showed a lower apparent digestibility coefficient of INSP(P<0.05)in the terminal ileum(CAID)and total digestive tract(CATTD)than those of YAD and MYD,diets of different yeast source had a significant influence on digestibility mannose(P=0.031)of INSP in the terminal ileum.Furthormore,the TNSP(P<0.05)of DBY has a lower CAID and CATTD than YAD and MYD,different yeast source diets had a significant influence on digestibility of TNSP's Man(P<0.05)in the terminal ileum and total digestive tract.But SNSP of YAD had a lower CAID and CATTD than DBY and MYD.The results of amino acid showed that the content was highest in YAD,and lowest in MYD.The CAID of valine(P=0.018)and methonine(P=0.003)in YAD were lower than that of DBY and MYD;the source of yeast product had a significant influence on CAID of isoleucine(P=0.010),leucine(P=0.018)and phenylalanine(P=0.025),histidine(P=0.033)of MYD had a higher CAID than YAD.Generally speaking,the content of NSP in three dies were not high,YAD and MYD had a higher CAID and CATTD of NSP than DBY,MYD had the highest CAID of AA than YAD,DBY was lowest.Most nutritional composition of MYD had a higher apparent digestibility in the terminal ileum and total digestive tract than YAD and DBY.Experiment 2 The Growth Performance of Pigs Fed Different Protein-rich Yeast ProductsThe aim of this experiment was to evaluate the feasibility of substituting heat treated soybean meal with the three yeast products based on the average daily feed intake(ADFI),average daily gain(ADG)and feed conversion(F:G)of the tested herds.Ten percent of heat treated soybean meal in the control diet was replaced with one of the 3 yeast products,i.e.,dry yeast,autolyzed yeast and micro-ground yeast,to formulate 4 test diets with similar digestible energy and amino acid content.One hundred and sixty male castrated crossbreed(DurocxLandracex Large white)growing pigs with an average initial body weight of 20kg±0.5kg were selected,which were divided into 4 groups with 40 pig in each group.The results showed that different yeast source diets have no significant influence on ADFI(P=0.277)and ADG(P=0.728).Precisely speaking,three yeast source diets have a higher ADFI and ADG than control group and YAD has the greatest ADG and ADFI.The F:G(P=0.438)has no significant influence by different diets,the F:G of control group is lowest and the DBY is highest in four groups.Generally speaking,yeast source diets can improve the ADFI and ADG,but can't influence the F:G.