Optimization of exogenous complex enzyme ratio and its effect on in vitro fermentation characteristics of calf diet
The purpose of this experiment was to study the optimum ratio of exogenous complex enzymes and explore their effects on the fermentation characteristics of calf diet in vitro.The optimum proportion of five enzymes(phytase,amylase,cellulase,pectinase,and protease)was determined by orthogonal design to simulate the rumen fermentation model.The exogenous complex enzymes were added to the diet of calves,and were cultured in vitro for 2,4,6,8,10,12,24,and 48 hours.The gas production(GP),dry matter degradation rate(DMD),and fermentation parameters of the control group and the experimental group were measured at each time point.The results showed that the optimum dosage of five enzymes was phytase 150 U/g,amylase 150 U/g,cellulase 600 U/g,pectinase 1 200 U/g,and protease 600 U/g,and the optimum ratio was 150∶150∶900∶600∶600.Compared with the control group,the contents of DMD,GP,ammonia nitrogen(NH3-N),microbial protein(MCP),total volatile fatty acid(TVFA),acetic acid,propionic acid,and the ratio of ethylene to propylene(A/P)in the fermentation broth of the experimental group were extremely increased(P＜0.01).The study indicates that the addition of exogenous complex enzymes in diet can effectively increase the fermentation of GP and DMD in vitro and improve the rumen fermentation characteristics in vitro.
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