Effects Of Different Nitrogen Sources On Utilizable Crude Protein (uCP) And Rumen Fermentation In Vitro

The objective of the experiments was to study the effects of different nitrogen sources on utilizable crude protein (uCP) and rumen fermentation in vitro. In the experiments, the in vitro gas production technique and in vitro incubation technique of Zhao & Lebzien (2000) were used, and the buffers for the incubation solution were adjusted. Seven feed samples were concluded, and four rations with different concentrate level and E-N value were formulated with these samples. Four nitrogen sources were used in the experiments, i.e. urea, casein, lysine and methionine. It was carried out in three trials. The pH value, NH3-N concentration, disappearance rate, gas production and Utilizable Crude Protein (uCP) were analyzed.The results indicated that: (1) The pH value and the NH3-N concentration in the treatments added nitrogen sources were significantly higher (p<0.05) than that in the control, and the gas production reduced significantly owing to the nitrogen sources (p<0.05) . In comparison with the control, all nitrogen sources except for urea increased significantly the rate of disappearance. (2) The pH value and NH3-N concentration of treatments with casein or urea were fluctuated acutely according to the change of nitrogen level and the concentrate level of rations, but which of the amino acid-added groups were correspondingly stable. (3) Supplementation of lysine and methionine increased the production of uCP (p<0.05), which was positively correlated with the level of lysine (R2=0.93) and methionine (R2=0.67). (4) The amino acid concentration in the ration can affect the efficiency of the aa added. The lower this concentration is, the better the efficiency will be.It was inferred that supplementation of unprotected anima acid increased the content of uCP. However, casein and urea had little effect on the production of uCP, and the degradation of the unprotected casein and urea was not in favor of rumen fermentation, so the nitrogen sources of casein and urea should be protected to reducing the waste of nitrogen sources and disordering the rumen.