| Twelve mature semi-fine wool sheep with permanent cannulas were used in this study and they were devided into four blocks by weight and four groups by fed different diet. Diet treatments contained Yucca schidigera extract(YE) 0mg/kg,100 mg/kg,200 mg/kg and 300 mg/kg respectively in the basis diet. The experimental design was single factor randomized block experiment. Four experiments conducted to investigate nitrogen metabolism were as follows:In experiment 1, inhibitory effect of YE on ammonia concentration in rumen fluid in vitro was studied. Adding 0,100,1000,10000mg/L and 0,100,200,300,500,1000mg/L YE in rumen fluid with 1% urea, by measureing the ammonia concentration we ascertained the best YE concentration to inhibit urease. The results showed when at concertration of 300 mg/L, YE inhibited urease best. When lower or higher, the effect were less. In experiment 2, the effect of YE on rumen and blood parameter was studied. The result suggested that pH value was in the normal scale and it was little affected by YE. At 2 h after feeding, ammonia concentration was inhibited significantly. The inhibitory rate of Ammonia concentration of 100mg/kg,200mg/kg and 300mg/kg group were 17.17%,29.84% and 27.12% respectively, in which the 200mg/kg group had significant affect(p<0.05). The Urea-N concentration of ruminal fluid of every group were higher than the control group 11.96%,20.77% and 17.95% at 2h after feeding, also in which the 200mg/kg group had significant affect(p<0.05). At 2 h after feeding on No.7,14,21 and 28 day, ammonia concentration and Urea-N concentration were little affected by YE(p>0.05), which were same with Blood ammonia concentration and blood Urea-N concentration. Compared by the average number of protozoa in 28 days, the number of protozoa of 300mg/kg group was 9.81×104/ml, lower than control group(p<0.05) significantly.In experiment 3, the effect of YE on protein metabolism was studied. The trial was conduced twice in the later five days of No.2 and No.4 week. Compared by the average value of two trials, the urine urea concetration of 100mg/kg group,200 mg/kg group and 300 mg/kg group were lower than control group by 20.88%,31.90% and 18.79%(p>0.05). and the protein metabolism of 100mg/kg group and 300mg/kg were higher than control group by 6.89 and 4.4 percentage point. The 200mg/kg group's was 70.71%, which was significantly affected by YE(p<0.05). So YE administed at 200mg/kg diet could decrease content of urine urea, and increase diet protein metabolism significantly.In experiment 4, the rumen and blood parameter was studied with no YE in the diet. The trial began at the end of trial 2, and lasted for 7 days, in which all sheep were fed with control group diet. On No.4 and No.7 day, ammonia concentration in rumen increase a little, and Urea-N concentration were unchanged; blood urea concentration increase a little than control group and blood ammonia concentration kept unchanged(p>0.05).Master candidate: Tang Yan-junSupervisor: Prof. Li JieSpeciality:Animal nutrition and feed science... |
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