Effect Of Protective Methionine And Sustained-release Urea On Growth Performance And Blood Index Of Finishing Beef Cattle

The effects of different levels of rumen protective methionine(RPMet)and sustained-release urea(SRU)on rumen fermentation parameters and fiber degradation rate of ruminants were studied by batch culture in vitro in this experiment.And the optimal dosage of RPMet and RPMet were selected.Then twenty-four healthy fattening beef cattle of similar body weight were used as experimental animals.In this experiment,a complete randomized trial design was used,and the addition of RPMet and SRU was used as the experimental factor.The beef cattle were randomly divided into three groups,group I(control group),group ?(treatment group: 0.83 g/kg RPMet 13.33 g/kg SRU),group ?(treatment group 1.25 g/kg RPMet 13.33 g/kg SRU).The compound feed additive of RPMet and SRU was fed to beef cattle in each groups.The effects of compound feed additives of RPMet and SRU on growth performance,apparent digestibility of nutrients,blood biochemical indexes and the content of amino acids in blood of fattening beef cattle were studied.The results showed:(1)There were some effects on rumen fermentation parameters and fiber degradation rate in vitro in different dietary RPMet and SRU supplementation levels.And during the each culture period in vitro,the amount of gas production and the content of bacterial protein(BCP)in the group of 1.25 g/kg RPMet 13.33 g/kg SRU were higher than those in other groups.And the concentration of NH3-N in this group was in the optimal range.During the 2 h and 12 h culture period in vitro,The concentration of total volatile fatty acids(TVFA)and acetic acid in which group was the highest,and the degradation rate of fiber was relatively high at each culture time.(2)There was no significant effect on daily gain,feed intake,feed/feed ratio and apparent digestibility of DMCP and ADF in different dietary RPMet and SRU supplementation levels in fattened beef cattle.However,after adding RPMet and SRU,There was a tendency of increasing daily gain of beef cattle,apparent digestibility of various nutrients and decreasing feed / weight ratio.Especially,the digestibility of EE and NDF in the group of 1.25 g/kg RPMet13.33 g/kg SRU was significantly higher than that of control group(P<0.05).(3)When RPMet and SRU were added to the diet,the concentrations of ALB,TP and TG in the blood of beef cattle were increased,and the concentration of TAA,NEAA,His,Asp,Ser,Glu,Pro and BUN in the blood were decreased.Especially,the concentration of ALB,TP and TG were the highest,the concentration of BUN was the lowest,and the metabolism level of each amino acid were the best in the group with 1.25 g/kg RPMet 13.33 g/kg SRU.In summary,supplementation of RPMet and SRU in diet could promote rumen fermentation in beef cattle.And adding 1.25 g/kg RPMet 13.33 g/kg SRU to the diet of beef cattle could had the tendency of increasing daily gain,apparent digestibility of nutrients and decreasing feed / weight ratio,increase the concentration of BUN and TG in blood,and decrease the concentration of BUN and various kinds of amino acids in blood.