| Experiments were conducted to study the producing techniques and the effectiveness of protection and application of Rumen bypass methionine(RPMet),lysine(RPLys).Six RPMet and four RPLys products were obtained and their stability were evaluated by in vitro and in situ methods. Six RPMet were protected by polyoxylateⅣ(M1); polyoxylateⅣand ethyl-cellulose (M2); polyoxylateⅣand ethy1-cellulose and hydroxyprpoyl methylcellulose (M3); ethyl-cellulose (M4) dividely; polyoxylateⅣand hydrogenated vegetable tallow (M5); hydrogenated vegetable tallow (M6). Four RPLys were protected by polyoxylateⅣand ethyl-cellulose (L1); polyoxylateⅣand hydroxyprpoyl methylcellulose(L2); polyoxylateⅣand hydrogenated vegetable tallow (L3); ethyl-cellulose and hydrogenated vegetable tallow (L4) dividely. The results showed that nitrogen release rate were 11.7%～50.7% and 42.05%～75.02% respectively for M5 and L3 when incubated for 4, 8, 24 and 48 h in the rumen of four Holstein Friesian cows. Whereas the nitrogen release rate were 24.67～38.44% and 42.05～75.02% respectively when incubated for 4, 8, 24 and 48 h in the pH 6.6 buffer solution, There was a significant positive linear relationship between the degradability of RPMet and RPLys in rumen and that in pH 6.6 buffer solutions. The correlation coefficients were 0.8675 and 0.9630 for M5 and L3, respectively. Nitrogen release rate in abomasum, small intestine and pH2.4 buffer solution were all 100%. The effective degradability of M5 and L3 in the rumen were 30.49% and 51.04%, and 69.51% methionine and 48.96% lysine could enter small intestine accordingly.The effectiveness of the protection and application of RPMet were further evaluated by using 4 cannulated cows with a 4×4 Latin square experiment design. The results indicated that supplementing methionine coated with the polyoxylateⅣand hydrogenated vegetable tallow through rumen cannular could significantly improve the concentration of plasma free methionine in the jugular vein (6.55ug/ml) (P＜0.05), which is about 70.88% of that with duodenal infusions of methionine(9.24ug/ml). The concentrations of plasma free methionine were 2.71ug/ml and 3.20ug/ml of cows fed either with the basal diets or supplying Met in the rumen. The results also showed that supplying RPMet in the rumen could significantly increase the concentrations of free methionine in artery plasma and vena plasma of mammary gland (P＜0.05), whereas the concentrations were lower than that of infusing methionine into duodenum (P＜0.05).The extraction efficiency of methionine in artery plasma within mammary gland were 0.85% and 0.43% respectively. Supplementing RPMet in the rumen could significantly increase the concentrations of plasma urea nitrogen and milk urea nitrogen (P＜0.05). However milk yield, milk component, digestion and utilization of nitrogen, ruminal pH,the concentration of NH3-N and VFA were not significantly affected (P＞0.05).By comparing the supplementing Protected-Lysine to rumen and infusing Lysine into duodenum, the effectiveness of the protection and application of RPLys were further evaluated. Four beef catties with rumen, duodenum and ileum cannulars were used in a 4×4 Latin square experiment design. The results showed that supplying lysine coated with the polyoxylateⅣand hydrogenated vegetable tallow in the rumen could significantly improve the concentration of plasma free lysine in the jugular vein (11.18ug/ml) (P＜0.05), which is about 66.61% of that with duodenal infusions of lysine(16.97ug/ml). The concentrations of free lysine were 7.31ug/ml and 8.00ug/ml with the basal diets and supplementing of Lys in the rumen respectively. Supplementing RPLys in the rumen could significantly increase plasma urea concentration (P＜0.05), whereas had no effects on the ruminal pH, NH3-N, VFA, digestion and utilization of nitrogen (P＞0.05).
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