Effect Of Exogenous Enzyme Preparation In Corn Straw-based Diet On Growth Performance Of Lambs And Mechanism Of Its Action On Degradation Of Fiber Structure

Based on Dorperx Small Tail Han sheep crossbred male lambs and corn stalk,the feeding experiment was used to evaluation the effects of exogenous enzyme preparation in corn straw-based diets on growth performance,nutrient digestibility,slaughter performance and meat quality of lambs,and in situ and in vitro experiment were used to evaluation the effects of exogenous enzyme preparation on rumen degradation and in vitro fermentation characteristics of corn straw.The article studied systematically and explained the use of external enzymes and their mechanism of action in ruminants.The present research included two experiments listed as follow.Experiment 1:Effects of treating corn straw with different compatibility enzymes on growth performance,nutrient digestibility,slaughter performance and meat quality of Dorper x thin-tailed Han crossbred lambsThis experiment was conducted to investigate the effects of different compatibility enzymes on growth performance,nutrient digestibility,slaughter performance and meat quality of Dorper x small-tailed Han sheep crossbred male lambs fed corn straw-based diets.Lambs were assigned to one of four groups of 100 animals per group with five replicates in a randomized complete block design being:control(basal diet without any supplementation),Treatment groups(TG):TG I(basal diet with enzymes preparation of Cellulase + P-glucanase + Xylanase),TG?(basal diet with enzymes preparation of Cellulase + ?-glucanase + Xylanase + Pectase),or TG?(basal diet with enzymes preparation of Cellulase + ?-glucanase + Xylanase + Pectase + Laccase)in a 76-day experiment including a 10-day preliminary test period and a 66-day formal trial period.The basal diets as TMR was fulfilled the growth requirements of lambs according to NRC(2007)with a concentrate:forage ratio of 4:6(at first phase)and 5:5(at second phase)(DM basis).The exogenous enzyme preparation for treatment diets was dissolved in water to form a 4%solution containing a mix of carrier and enzymes,which was sprayed directly onto the corn straw at a rate of 1.0 kg/t of TMR(Air dry basis),just prior to feeding.The results showed as follows:different compatibility enzymes had significant effects on ADG and ratio of feed to gain(F/G)(P<0.05),but no significant differences were found in dry matter intake(P=0.107).ADG of TG? and TG II were significantly higher than those in Control and TG I(P<0.05),and F/G of TG? was significantly lower than that in Control(P<0.05),but there was no difference between TG? and TG II or Control and TG I(P>0.05),respectively.Addition of enzymes preparation also increased(P<0.05)apparent digestibility of all nutrients,except for CP(P=0.166).Apparent digestibility of DM,OM,GE,NDF,ADF in TG? and TG ? were significantly higher than that in Control and TG ?(P<0.05).TGIII was the highest in nutrient digestibility.The magnitude of improvement in digestibility varied among nutrients,with the highest improvement occurring in digestibility of DM and ADF(about 11%and 19%,respectively).The addition of enzyme preparation in TGIII also achieved good economic benefits.But no significant differences were found in slaughter performance,such as carcass weight,slaughter rate,complex stomach(rumen,reticulum and omasum,abomasum)and visceral organs(heart,liver,spleen,lung,kidney)of lambs between control and enzyme treatment group(P>0.05),and meet quality,such as nutrition,meat color,tenderness,and the content of fatty acids and amino acids were also not significantly affected(P>0.05).At the same time,rumen fermentation parameters(pH,ammonia nitrogen and VFA concentration)were not significantly affected by enzyme treatment(P>0.05).It is concluded that there are positive responses on growth performance and nutrient digestibility of fattening sheep for treating corn stalk diet with different compatibility enzymes,but no significant differences were found in slaughter performance and meet quality.The effect of TG?(Cellulase +?-glucanase + Xylanase + Pectase + Laccase)is significantly better than others in feeding of lambs.Compare with the Control,average daily gain of TG III was increased by 23.51%,nutrient digestibility was increased by 11%,feed conversion ratio was increased by 26.36%,and diet cost for 1kg weight gain was reduced by 18.42%.Experiment 2:Effects of exogenous fibrolytic enzyme on rumen in vitro fermentation parameters and degradability of corn strawThe objective of this study was to determine the effects of special fibrolytic enzymes for straw(SFES)on in vitro gas production(GP),fermentation characteristics,and in situ degradability of corn straw.Rumen liquor was obtained from three Dorper x Han crossbred male sheep fitted with permanent rumen cannulae fed a total mixed ration of a 45:55 concentrate and Chinese wildrye.The in vitro parameters and ruminal degradability of corn straw were estimated by in vitro and in vivo methods respectively.The trial of in vitro incubation consisted of three doses(0,0.1,0.5g/100g of substrate as air dry basis)of SFES and two time pretreatment(0,16h).For the in sacco degradability,different levels of SFES were added directly onto 2 g of corn straw in nylon bags and incubated in the rumen for 12,24,36,48 and 72h to estimate degradability of corn straw.The results showed as follows:?In in vitro fermentation test,Total GP and enzyme activity of FPA and CMCase were increased(P<0.05)from 3 to 12h at incubation period,and pH was significantly increased at 3h(P<0.05),and concentration of NH3-N,TVFA,Acetic acid,propionic acid and butyric acid were increased from 3 to 6h(P<0.05),and the peak values of two kinds of enzyme activities and GP were observed at 12h and 48h,respectively.The effect of SFES-H group on in vitro fermentation characteristics of corn straw was higher than that in control and SFES-L group.In the same dosage group,the effect of 16h pretreatment was worse than that of Oh treatment.? In rumen degradation test,ruminal effective degradability of DM,NDF,ADF,hemicellulose and cellulose were increased by SFES-H(P<0.05),but has no effect on ADL(P>0.05).Compare with the Control,SFES-L could improve the rumen degradability of DM?hemicellulose and cellulose(P<0.05),but has no effect on NDF?ADF and ADL(P>0.05).The degradation rates of DM,NDF,ADF,hemicellulose,cellulose and lignin were increased with the extension of time,and then tended to be stable after 48h.In other words,the high dose of SFES could improve the in vitro fermentation parameters and ruminal effective degradability of DM and crude fiber of corn straw,but had no effect on ADL.In conclusion,the outcome of this research indicated that the application of SFES could improve growth performance and nutrient digestibility of lambs,in vitro GP fermentation and rumen degradation of corn straw.The mechanism of action of SFES was probably by increasing activity of fibrolytic enzymes,especially CMCase in ruminal fluid to promote the degradation of rumen microorganisms and ruminal fiber degradation,so as to improve the nutritive value of straw.