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The aim of this study was to evaluate the effect of wet sorghum distillers grain(WSDG) as part of the diet concentrate on the lactating performance of dairy cows. Twenty-seven Holstein milking cows were selected which in the early lactation stage with an average weight of 550Kg, producing an average of 30Kg of milk daily. The cows were divided randomly into three groups and fed with different mixed rations. The diets were formulated according to NRC(1989) recommendations: (1)control diet (2)15% WSDG diet and (3)30% WSDG diet. Three different dietary treatments were formulated into iso-nitrogen and iso- energetic diets. After one week of adaptation period, the experimental feeding was conducted for 8 weeks. Three rumen canulated cows were also examined in order to investigate ruminal fermentation of three total mixed rations. In the other experiment, napiergrass were chopped and ensiled in laboratory silos. Prior to ensiling, the material was mixed with 0, 20%, 40%, and 60% WSDG. Laboratory silos were opened at 0, 1, 2, 4, 8, 16, and 32 days after ensiling and analyzed the composition of silage. The results showed that the milk yield corrected by the 3.5% fat standard, showed no significant difference between the control、15%WSDG and 30% WSDG treatment groups(P>0.05). The daily dry matter intake of the control group was higher than the other groups(P<0.05). In respect to the milk composition, milk fat, milk protein and total solids, showed no difference among the treatment groups(P>0.05). The protein and energy efficiency of the 30% WSDG group was significantly higher than the other treatment groups(P<0.05). Ruminal pH value was no different among the treatment groups(P>0.05). Ammonia-nitrogen concentration in the control group was higher than the other groups(P<0.05). The concentration of total ruminal volatile fatty acids and the ratio of acetic acid to propionic acid were similar in all dietary groups. The results of silage experiment at 32 days showed that the pH value of 40% group was significantly lower than the other treatment groups(P<0.05). Titratable acidity, buffering capacity and water-soluble carbohydrate of the control group was significantly lower than the other groups(P<0.05). Lactic acid production of 20% WSDG group was significantly higher than the other treatment groups and the control group was lower(P<0.05). The ammonia-nitrogen concentration of total N showed that 60% group was significantly lower than the other groups(P<0.05). In respect to the Flieg score, the control was 85, 20% group was 93, 40% group was 95 and 60%group was 91.
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