| A series of in vitro and in vivo experiments were conducted to explored the possibility and efficacy of methylolurea as NPN of ruminants. In the first experiment a in sacco method was employed to see the dynamic dispperance of mythylolureas of different degree polymerization in dairy cow rumens.Then a continuous culture fermentation experiment were done to see the effects of mythylolureas of different degree polymerization on rumen fermentation characteristics. A suitable methylolurea was chosen for the followed experiments based on the results of the first two experiments. In experiments with dairy cows the optimal addition rate in concentrate supplement was selected firstly based on the results of production performances and nitrogen metabolism. Then the other experiment was conducted to compare the effects of different NPN on production performances,nitrogen metabolism and rumen fermentation characteristics. In experiments with beef cattle, one experiment was conducted to determine the optimal addition level in concentrate supplement for finishing beef; then the other experiment was conducted to compared the effects of different NPN on growth performances and nigrogen metabolism.The last experiment was conducted to determined the optimal addition level of methylolurea in Liaoning Cashmere Goat.Experiment 1. This study was aimed to see the rumen degradation of methylolurea with different degree of polymerization with reference of urea. The results showed that urea disappeared totally from nylon bags within 1 hour of incubation. Methylolureaâ… 100% disappeared from nylon bags within 4 hours of incubation. Methylolureaâ…¡disappeared 100% until 12 hours after incubation and methylolureaâ…¢91% disappeared from nylon bag by 30 hours after incubation. So it was concluded that Methylolureaâ…¡and methylolureaâ…¢might be better from the point of view slow release urea.Experiment 2. the effects of different mythylolureas with reference of urea on rumen microbial fermentation were test in a continuous culture system. The results showed that the digestibility of DM,OM,NDF and ADF methylolureaâ…¡were all the highest among different treatments. The baterial efficiency, expressed as grams of bacterial N per kilogram of OM digested were 8.46,9.34, 12.18 and 10.05 for urea treatment,mythylolureaâ… treatment, mythylolureaâ…¡treatment and mythylolureaâ…¢treatment, respectively. The total VFA production of mythylolureaâ…¡treatment was also the highest among different treatments. The dynamic ammonia release pattern of mythylolureaâ…¡and mythylolureaâ…¢treatment treatment was more stable than other treatments. However, the ammonia concentration of different time in fermentators of mythylolureaâ…¡treatment were higher than that of mythylolureaâ…¢treatment. So it concluded that mythylolureaâ…¡might be the suitable NPN in this study.Experiment 3. The objective of this study was to determine the optimal supplemental rate of the mythylolurea for dairy cows. A control diet was formulated with supplemental NPN. The treatments were 0.7% methylolurea,1.4% methylolurea and 2.1% methylolurea supplement in concentrate of dairy cow. The results showed that supplement 2.1% methylolurea in concentrate decreased the milk production significantly(p<0.05). The milk production of 1.4% methylolurea treatment was 1.12kg/d lower than that of the control group, however, it was not statistically significant. There were no differences among treatments in terms of nutrient digestibility, however, the urine nitrogen went up with increased supplemental levels of mythylolurea in dairy cow concentrate. The urine nitrogen of control group,0.7% methylolurea,1.4% methylolurea and 2.1% methylolurea were 153.48 g/d,159.14 g/d,179.65 g/d and 197.00g/d, repectively. The serum urea nitrogen concentration and milk urea nitrogen concentration increased linearly with increased supplemental level of methylolurea. Milk urea nitrogen of 2.1% methylolurea treatment went up to 17.63mg/dl, which was around upper limit of the recommended range and suggesting that 2.1% supplemental level was too high for the dairy cows in this study. There were no significant impact of methylolurea supplement on blood biochemical parameters which were indicative of liver function.Experiment 4. The objective of this study was to test effects of different NPN on dairy cow production performances,nitrogen metabolism and rumen fermentation. Four ruminally canulated dairy cows were used with a Latin Square design. A diet with no supplemental NPN were formulated as control. And the treatment were addition of urea,mythylolurea and starea. All diets were isoenergenic and isonitrogenic. The results showed that the milk yields of control group, urea group, methylolurea group and starea group were 21.34kg/d,18.28kg/d,20.16kg/d and 21.35kg/d, repectively. Milk yield of Urea group was lower than other groups. NPN sources did not change the dietary nutrient digestibility. However, nitrogen utilization efficiency (milk nitrogen/intake nitrogen) of urea treatment were lower than other groups. NPN sources had not impact on the blood biochemical parameters. Rumen fermentation characteristics indicated the starea and methylolurea were both slow release NPN, however, methylolurea was better slow release in term of ammonia release rate. The rumen ammonia concentration of methylolurea group 6 hours after feeding were higher than that of other groups.Experimemt 5. The objective of this study was to determine optimal supplemental level of methylolurea in concentrate supplement of finishing beef. A diet of totally plant protein origin were formulated as control. The treatments were 0.7%,1.4% and 2.1% methylolurea in supplement concentrate of beef. The results showed that supplement methylolurea at rate of 0.7% and 1.4% in beef supplement concentrate had no influences on ADG compared with control group. The ADG of control group,0.7% methylolurea group and 1.4% methylolurea group were 0.899kg,0.885kg and 0.896kg, respectively. However, the ADG of 2.1% methylolurea group were lower than that of other groups(P<0.05). The blood urea nitrogen and urine nitrogen were both went up linearly as the supplemental rate of methylolurea increased. The blood urea content and urine nitrogen excreted were significantly higher than that of other groups. Addition of different levels of methylolurea did not have impact on the blood biochemical parameters indicative of liver functions. It was concluded methylolurea added at a rate of up to 1.4% in beef supplement concentrate had no detrimental effects on production performances and animal health.Ecperiment 6. This study compared supplementation of different NPN on finishing beef performances and nitrogen metabolism with the reference of plant protein control group. The ADG of control group, starea group,methylolurea group and urea group were 0.756kg,0.735kg,0.833kg and 0.806kg, repectively. The ADG of methylolurea group was higher than that of starea group(P<0.05) and there were no significant differences among other groups(P<0.05). The nitrogen utilization efficiency (N retention/N intake) of different groups followed the same pattern of ADG of groups. The serum urea nitrogen content of groups was in order of urea group>starea group>methylolurea>control group.Experiment 7. This study was to determine the optimal addition rate of methylolurea in diet of Liaoning Cashmere wether. Methylolurea was added at rate of 5g,7.5g and lOg to substitute the respective nitrogen-equivalent amount of soybean meal of control group diet, which was 22%,34% and 46% of the dietary soybean meal,repectively. The results showed that there were no statistical differences among groups in terms of body weight gain and cashmere yield. However, the 22% group,34% group and 46% group resulted in 30%,51% and 35% more profit than the control group. |
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