Evaluation Of Degradability Of Feed Nutrients By Nylon Bag Method And In Vitro Gas Production Method

In this study,the rumen dynamic degradation parameters of the feed were obtained by nylon bag method,and the effective degradation rate was calculated.The degradation characteristics of the feed were studied.Then,the in vitro gas production characteristics of the feed were evaluated by the method of in vitro gas production,and the gas production data at the corresponding time point were obtained.The prediction model of the rumen degradation rate of the feed was established by using the in vitro gas production data.This study also predicted the metabolizable energy value and in vitro organic matter digestibility with in vitro gas production parameters.A total of 24.8(±1.4)kg of Nanjiang yellow sheep with permanent rumen fistula were used as experimental animals.The degradation rate of DM,CP and NDF of five kinds of roughage of alfalfa(ALF),rice straw(RS),distiller’s grain(DG),Perennial ryegrass(PRG),and Hemathria sibirica(HSB)were determined by nylon bag method;The degradation of com(CR),wheat bran(WB),soybean meal(SM),cottonseed meal(CM)and fish meal(FM)of five kinds of feed rate of CP,DM.Roughages were incubated in rumen for 0,2,6,12,24,36,48 and 72 hours,and the concentrates were incubated for 0,2,4,8,12,24 and 48 hours.The results showed that the disappearance rate of DM and CP in alfalfa was the highest(P<0.01),followed by distiller ’s grains.The dry matter degradation rate of straw was the lowest in all incubation times(p<0.01).The NDF degradation rate did not change significantly(P>0.01)between 12 and 72 hours,except that the NDF loss rate was significantly lower than that of other roughage.The order of effective degradation rate of DM in CR(66.78%)>SM(57.13%)>WB(50.36%)>CM(39.82%)>FM(37.56%).The order of effective degradation of CP was:WB(72.83%)>CR(64.71%)>SM(59.41%)>CM(49.68%)>FM(43.15).Ten kinds of common feeds were used as fermentation substrate in vitro.The incubation time of roughage was 0,2,6,12,24,36,48,72,concentrate to develop 0,2,4,8,12,24,48 hours.The gas production of each feed at each time point was obtained.The main results were as follows:from the beginning of 6h,the gas production rate of alfalfa was the highest(P<0.01),followed by distiller’s grains(P<0.01).Between 24 and 72 hours of PRG and HSB gas production is not significantly different.SM in feed gas production began slowly,since 12h gas production increased gradually,higher than that of FM,WB and CM.The data of rumen degradability and gas production were analyzed,and the three order equation was obtained.There was a good correlation between the yield of ten kinds of feed and the degradation rate of each component.Ruminal degradation rate and gas production of the three order function R2 are greater than 95%.The above results show that in the analysis of the degradation performance of the commonly used feed,the in vitro gas production method can replace the nylon bag method to obtain the degradation rate of the feed quickly.Concentrated feed gas production order:CR>SM>FM>WB>CM.Prediction of IVOMD and ME:Roughage:ALF>DG>RS>PRG>HSB.Concentrate CR>SM>FM>WB>CM.