| Seven experiments were conducted to investigate the effects of novel urease inhibitor Hydroquinone (HQ) on apparent nutrient digestibility, rumen fennentation, nitrogen metabolism and production performance of ruminants, and to estimate the optimal adding level of HQ in total mixed ration for ruminants In experiment 1, effect of HQ on rumen urease activity was studied firstly in vitro. Hydroquinone at concentration of0.Olppm, 0.1 ppm, lppm and loppm inhibited urease activity of intact rumen microbes by 25%, 34%, 55% and 64% respectively, compared with the control. Rumen urease that was partia]ly purified in the presence of 0.025% P -mercaptoethanol was calculated as I 04.28IUImg based on the protein content of the urease solution. The Km for the enzyme was 2X 1W molIL with Vmax of 319.44 ~ moles/mm. The inhibition Kinetics with partially purified rumen urease was also investigated. The results showed that the inhibitory effect was not eliminated by increasing urea concentration, indicating a noncompetitive effect in nature with inhibition constant 1.2X 1W mollL. A parallel study was made to compare inhibitory effect of Hydrequinone with that of acetohydroxamic acid on rumen urease when the two inhibitors were present in equimolar concentration. The results demonstrated that acetohydroxamic acid at concentration of lppm and loppm reduced urease activity by 2526% and 61.5% respectively (P<0.05) . It was obvious that HQ was more effective inhibitor of rumen urease than acetohydroxamic acid at lower dosage of urease inhibitor. The above results suggested that HQ could be a potent inhibitor of rumen urease in vitro. In experiment 2, four local sheep with runien fistula were used in change-over design to determine the effect of hydroquinone (HQ) on some runiinal enzymes and viable counts of rumen microorganism in sheep. The results showed that HQ significantly decreased urease activity by 65%(P<0.01) and increased cellulase activity by 28%(P<0.05 ) inthe sheep given 50mg of HQ per day by intramminal infusion. HQ had no adverse influence on other ruminal enzymes and viable counts of rumen microorganism at this dose. Growth rate of rumen bacteria was unaffected by 10,20,40 ppm of HQ with exception to 8oppm of HQ. The estimate of bacterial numbers and the trial of bacterial inhibition indicated that HQ did no damage to rumen microorganism within the range of dosage tested. It indicated that HQ was a specific inhibitor of rumen urease without any negative effect on nimen microorganism and their host safety in vivo. In experiment 3, twelve cannulated ram were used to investigate effect of HQ on the characteristics of rumen fermentation. The animals were randomly assigned within initial live .4. 2001.5 weight block to one of four lreaUnents, which included 0 (control), 20, 40 or 80 ppm (DM basis). Ammonia concentration and pH value of nmiinal fluid were measured immediately at 0, 2,4,6 and 8 h after feeding. Thereafter, Urea and volatile fatty acids (VFA) were analyzed at the same sampling points. Rumen pH at different time interval was unaffected by supplemented HQ (P>0.05) . Ammonia concentration in animals receiving HQ was approximately one-half of that in animals not receiving HQ at the time of ammonia peak concentration (2 h postfeeding) (P<0.05) . However, there was no significant difference (P<0.05) inammonia concentration in the rumen between control and the HQ supplemented group at the other sampling lime except for 80 ppm HQ supplemended group at 4... |
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