| Two experiments were carried out to study effect of urea,urease inhibitor, dietary cation-antion balance on digestion and metabolism of nutrients, parameters of rumen and plasma of sheep.Experiment I: Five combinations of urea and AHA were disigned to slecte rational one in vitro. The result indicated that: (1) The pH of all combinations ranged from 6.01 to 6.55;They raised from 1-4h,but declined suddenly at 4h; (2) The NH3-N concentration peaks of B,C,D were at 1h, and slowly decreased at other hours; A, E appearsed peaks after 2h, but decreased after 4h, E exceptionally rapidly. (3) The DM vanishing rate of B group changed gently at the first, but had the trend of increasing after 6h. The conclusion was that reasonable combination of Urea and AHA was 1.5% and 25mg/Kg.Experiment II: In a 4×4 Latin square design, 8 Gasu High Mountain fine-wool fitted with permanent rumen fistula were given 4 diets [DCAB(Na++K+-Cl-) was 25(A), 35 (B), 45 (C), 55meq/100gDM(D)], and it was 64 days. The results indicated that: (1) The pH value in the rumen fluid of all treatments ranged from 6.21 to 6.94(P>0.05); (2) Ammonia nitrogen concentration means of B, C, D were less than A (P<0.05); B was less than A at 1h, 3h, 5h, 7h (P<0.05); After 1h fed, D was less than A, B, C (P<0.05); B changed between 4.47~49.67mg/100ml. (3) Urea nitrogen concentation mean of B was more than A, C, D (P < 0.05). (4) Concentration means of all treatments of acetic acid, propionic acid, butyric acid, TVFA and A/P value in rumen liquor were not significant at all time (P>0.05); Propionic acid concentrations of B, D were more than A, C (P=0.08),;Butyric acid concentration of A was more than B, C, D (P=0.06), A/P value B, D were less than A, C (P=0.07); (5)Apparent digestibilities of all treatments of DM, OM, ADF was significant (P<0.05); Apparent digestibilities of DM, OM, NDF, ADF of B were more than others (P<0.05). (6)All indexes of nitrogen balance of all treatments were not significant (P>0.05), but nitrogen metabobility of B was more than A, C, D (P=0.065). (7) Apparent digestibilities of Ca of B was more than A, C, D (P=0.068); Apparent digestibilities of P of B, C, D were more than A (P<0.05). (8) The intake of K of D was less than A, B (P<0.05). B, C were less than A (P<0.05); There were not significant faeces K and Na, urine K and Na, and apparent digestibilities of 4 treatments(P>0.05); The intake of Na of D was remarkably more than others(P<0.05); Apparent metabobilities of Na of B, D were more than A, C (P<0.05). (9) With DCAB levels increased, concentrations of PUN tended to decrease(P> 0.05); After fed 3h, D was less than A, B, (P< 0.05); After fed 5h, B, C, D were less than A (P<0.05). (10)There were not significant blood plasma of concentration TAA, Ca, P and urine TAA, but all indexes of B were favorable (P>0.05). The conclusion was that B was best among all treatments.Based on above all mentioned, there was a conclusion that the diet with 1.5% urea, 25mg/Kg AHA, and 35meq/100gDM DCAB was advantageous to rumen parameter, nutrients metabolism and digestion, health of sheep, which can enhance their productivties.
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