羟甲基脲作为反刍动物NPN的研究
摘要
本研究通过体外和活体试验研究了羟甲基脲作为反刍动物NPN的可行性和有效性。体外试验通过尼龙袋法测定了不同聚合度羟甲基脲的瘤胃降解速率,用持续双外流培养装置研究了不同聚合度羟甲基脲对瘤胃发酵的影响,从而筛选出聚合度适宜的羟甲基脲。然后分别利用奶牛和肉牛进行适宜添加水平的筛选和不同NPN的应用比较,并在绒山羊上做了推广试验。在奶牛研究部分中首先通过饲养试验和氮平衡试验研究了该聚合度羟甲基脲在奶牛精补料中的适宜添加比例,在此基础上比较了不同NPN产品对奶牛生产性能和瘤胃发酵的影响；同样在肉牛研究部分首先研究了该羟甲基脲在肉牛精补料中的适宜添加比例,然后比较了不同NPN产品对肉牛生产性能和氮代谢的影响。最后通过添加不同剂量的羟甲基脲研究了羟甲基脲在绒山羊生产中应用的可行性。
试验一、不同聚合度羟甲基脲瘤胃降解率的研究。本试验以尿素为对照,采用尼龙袋法比较了三种聚合度羟甲基脲的瘤胃降解率。结果表明尿素在1小时内从尼龙袋100%消失,羟甲基脲Ⅰ在4小时内100%消失,羟甲基脲Ⅱ12小时内100%消失,而羟甲基脲Ⅲ30小时的消失率仅为91%。羟甲基脲Ⅱ和羟甲基脲Ⅲ缓释效果较为明显。
试验二、不同聚合度羟甲基脲对瘤胃发酵的影响。本试验利用持续双外流培养装置以尿素为对照研究了不同聚合度羟甲基脲对瘤胃发酵的影响。试验结果表明羟甲基脲Ⅱ处理中DM、OM、NDF和ADF的消化率均高于其它三个处理,尿素处理、羟甲基脲Ⅰ处理、羟甲基脲Ⅱ、羟甲基脲Ⅲ处理的瘤胃微生物合成效率分别为8.46、9.34、12.18和10.05gN/kgOMTD,以羟甲基脲Ⅱ处理组为最高。羟甲基脲Ⅱ处理组的挥发性脂肪酸总量也最高,从氨态氮浓度动态变化规律看羟甲基脲Ⅱ处理组和羟甲基脲Ⅲ处理组的氨态氮释放均比尿素和羟甲基脲Ⅰ处理平稳,羟甲基脲Ⅲ处理各时间点的氨态氮浓度低于羟甲基脲Ⅱ处理组。因此本试验中羟甲基脲Ⅱ聚合度较为适宜。
试验三、不同羟甲基脲添加水平对奶牛生产性能及氮代谢的影响。以植物蛋白日粮为对照,比较奶牛精料补充料中分别添加0.7%、1.4%和2.1%羟甲基脲对奶牛生产性能和氮代谢的影响。试验结果表明精补料中添加2.1%羟甲基脲显著降低了奶牛产奶量,添加1.4%羟甲基脲时产奶量的降低尽管没有达到统计学的显著水平,但与植物蛋白对照相比其产奶量下降了1.12kg/d。羟甲基脲添加水平没有显著影响日粮营养成分的消化率,但从氮代谢看,随着添加水平的提高奶牛尿氮的排出增加,植物蛋白组、羟甲基脲Ⅰ组、羟甲基脲Ⅱ组、羟甲基脲Ⅲ组每天排出的尿氮分别为153.48g/d、159.14 g/d、179.65 g/d、197.00 g/d,血清尿素氮和牛奶尿素氮随着羟甲基脲添加水平的提高也表现出线性上升的过程,特别是2.1%羟甲基脲组的牛奶尿素氮可达到17.63mg/dl,处于推荐的上限,说明2.1%的羟甲基脲添加水平过高。从血液生化指标及肝功指标来看,不同添加水平的羟甲基脲均没有给奶牛健康带来不良影响。因而奶牛精补料中羟甲基脲的适宜添加水平为0.7-1.4%。
试验四、不同NPN对奶牛生产性能、氮代谢和瘤胃发酵的影响。以植物蛋白为对照,按照等能、等氮的原则比较了尿素、羟甲基脲及糊化淀粉尿素对奶牛生产性能、氮代谢和瘤胃发酵的影响。结果表明植物蛋白组、尿素组、羟甲基脲组和糊化淀粉尿素组的产奶量分别为21.34±3.21kg、18.28±4.23kg、20.16±2.76kg和21.35±3.59kg,尿素组产奶量显著低于其它三组。不同NPN来源没有显著影响日粮营养成分的消化率,但尿素处理的氮素转化效率(牛奶氮/进食氮)低于植物蛋白组、羟甲基脲组和糊化淀粉尿素组。添加不同NPN没有对奶牛血液生化指标造成显著的影响。瘤胃发酵指标的测定结果表明糊化淀粉尿素和羟甲基脲对尿素都有缓释作用,但羟甲基脲的缓释效果更好,该处理瘤胃氨态氮浓度在6小时以后显著高于其它处理。
试验五、不同羟甲基脲添加水平对肉牛生产性能及氮代谢的影响。以植物蛋白组为对照,研究了在肉牛精料补充料中分别添加0.7%、1.4%和2.1%羟甲基脲对肉牛生产性能和氮代谢的影响。结果表明添加0.7%和1.4%羟甲基脲对肉牛日增重没有显著的影响,植物蛋白组、0.7%羟甲基脲组和1.4%羟甲基脲组的平均日增重分别为0.899kg、0.885kg和0.896kg,没有显著差异(P>0.05),但当添加水平达到2.1%时肉牛日增重为0.815kg,明显低于其它三组。随着羟甲基脲添加水平的提高肉牛血清尿素氮和尿氮排出均升高,2.1%羟甲基脲组的血清尿素氮和尿氮排量显著高于其它三组。因此在本试验条件下羟甲基脲的适宜添加水平为1.4%左右。添加不同水平羟甲基脲对肉牛血液生化指标没有不良影响。
试验六、不同NPN对肉牛生产性能和氮代谢的影响。以植物蛋白日粮为对照,按照等能、等氮取代的原则研究了肉牛精料补充料中添加羟甲基脲、尿素和糊化淀粉尿素对肉牛生产性能和氮代谢的影响。植物蛋白组、糊化淀粉尿素组、羟甲基脲组和尿素组的日增重分别为0.756kg、0.735kg、0.833kg、0.806kg,其中羟甲基脲组明显高于糊化淀粉尿素组(P<0.05),其它组间差异不显著(P>0.05)。氮素利用效率(沉积氮／食入氮)与日增重趋势相一致。血清尿素氮以尿素组最高,其次是糊化淀粉尿素组,再次是羟甲基脲组,植物蛋白处理组最低。添加使用各种NPN没有对肉牛血液生化指标造成不良的影响。
试验七、不同水平羟甲基脲对绒山羊生产性能的影响。用羟甲基脲分别取代基础日粮中22%、34%和46%的豆粕,研究不同添加水平羟甲基脲对辽宁绒山羊增重和产绒效果的影响。结果表明各处理之间日增重和产绒量差异不显著。但22%处理、34%处理和46%处理分别比对照组增收30%、51%和35%。经济效益显著。
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. MethylolureaⅠ100% disappeared from nylon bags within 4 hours of incubation. MethylolureaⅡdisappeared 100% until 12 hours after incubation and methylolureaⅢ91% disappeared from nylon bag by 30 hours after incubation. So it was concluded that MethylolureaⅡand methylolureaⅢmight 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 methylolureaⅡwere 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,mythylolureaⅠtreatment, mythylolureaⅡtreatment and mythylolureaⅢtreatment, respectively. The total VFA production of mythylolureaⅡtreatment was also the highest among different treatments. The dynamic ammonia release pattern of mythylolureaⅡand mythylolureaⅢtreatment treatment was more stable than other treatments. However, the ammonia concentration of different time in fermentators of mythylolureaⅡtreatment were higher than that of mythylolureaⅢtreatment. So it concluded that mythylolureaⅡmight 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.
试验一、不同聚合度羟甲基脲瘤胃降解率的研究。本试验以尿素为对照,采用尼龙袋法比较了三种聚合度羟甲基脲的瘤胃降解率。结果表明尿素在1小时内从尼龙袋100%消失,羟甲基脲Ⅰ在4小时内100%消失,羟甲基脲Ⅱ12小时内100%消失,而羟甲基脲Ⅲ30小时的消失率仅为91%。羟甲基脲Ⅱ和羟甲基脲Ⅲ缓释效果较为明显。
试验二、不同聚合度羟甲基脲对瘤胃发酵的影响。本试验利用持续双外流培养装置以尿素为对照研究了不同聚合度羟甲基脲对瘤胃发酵的影响。试验结果表明羟甲基脲Ⅱ处理中DM、OM、NDF和ADF的消化率均高于其它三个处理,尿素处理、羟甲基脲Ⅰ处理、羟甲基脲Ⅱ、羟甲基脲Ⅲ处理的瘤胃微生物合成效率分别为8.46、9.34、12.18和10.05gN/kgOMTD,以羟甲基脲Ⅱ处理组为最高。羟甲基脲Ⅱ处理组的挥发性脂肪酸总量也最高,从氨态氮浓度动态变化规律看羟甲基脲Ⅱ处理组和羟甲基脲Ⅲ处理组的氨态氮释放均比尿素和羟甲基脲Ⅰ处理平稳,羟甲基脲Ⅲ处理各时间点的氨态氮浓度低于羟甲基脲Ⅱ处理组。因此本试验中羟甲基脲Ⅱ聚合度较为适宜。
试验三、不同羟甲基脲添加水平对奶牛生产性能及氮代谢的影响。以植物蛋白日粮为对照,比较奶牛精料补充料中分别添加0.7%、1.4%和2.1%羟甲基脲对奶牛生产性能和氮代谢的影响。试验结果表明精补料中添加2.1%羟甲基脲显著降低了奶牛产奶量,添加1.4%羟甲基脲时产奶量的降低尽管没有达到统计学的显著水平,但与植物蛋白对照相比其产奶量下降了1.12kg/d。羟甲基脲添加水平没有显著影响日粮营养成分的消化率,但从氮代谢看,随着添加水平的提高奶牛尿氮的排出增加,植物蛋白组、羟甲基脲Ⅰ组、羟甲基脲Ⅱ组、羟甲基脲Ⅲ组每天排出的尿氮分别为153.48g/d、159.14 g/d、179.65 g/d、197.00 g/d,血清尿素氮和牛奶尿素氮随着羟甲基脲添加水平的提高也表现出线性上升的过程,特别是2.1%羟甲基脲组的牛奶尿素氮可达到17.63mg/dl,处于推荐的上限,说明2.1%的羟甲基脲添加水平过高。从血液生化指标及肝功指标来看,不同添加水平的羟甲基脲均没有给奶牛健康带来不良影响。因而奶牛精补料中羟甲基脲的适宜添加水平为0.7-1.4%。
试验四、不同NPN对奶牛生产性能、氮代谢和瘤胃发酵的影响。以植物蛋白为对照,按照等能、等氮的原则比较了尿素、羟甲基脲及糊化淀粉尿素对奶牛生产性能、氮代谢和瘤胃发酵的影响。结果表明植物蛋白组、尿素组、羟甲基脲组和糊化淀粉尿素组的产奶量分别为21.34±3.21kg、18.28±4.23kg、20.16±2.76kg和21.35±3.59kg,尿素组产奶量显著低于其它三组。不同NPN来源没有显著影响日粮营养成分的消化率,但尿素处理的氮素转化效率(牛奶氮/进食氮)低于植物蛋白组、羟甲基脲组和糊化淀粉尿素组。添加不同NPN没有对奶牛血液生化指标造成显著的影响。瘤胃发酵指标的测定结果表明糊化淀粉尿素和羟甲基脲对尿素都有缓释作用,但羟甲基脲的缓释效果更好,该处理瘤胃氨态氮浓度在6小时以后显著高于其它处理。
试验五、不同羟甲基脲添加水平对肉牛生产性能及氮代谢的影响。以植物蛋白组为对照,研究了在肉牛精料补充料中分别添加0.7%、1.4%和2.1%羟甲基脲对肉牛生产性能和氮代谢的影响。结果表明添加0.7%和1.4%羟甲基脲对肉牛日增重没有显著的影响,植物蛋白组、0.7%羟甲基脲组和1.4%羟甲基脲组的平均日增重分别为0.899kg、0.885kg和0.896kg,没有显著差异(P>0.05),但当添加水平达到2.1%时肉牛日增重为0.815kg,明显低于其它三组。随着羟甲基脲添加水平的提高肉牛血清尿素氮和尿氮排出均升高,2.1%羟甲基脲组的血清尿素氮和尿氮排量显著高于其它三组。因此在本试验条件下羟甲基脲的适宜添加水平为1.4%左右。添加不同水平羟甲基脲对肉牛血液生化指标没有不良影响。
试验六、不同NPN对肉牛生产性能和氮代谢的影响。以植物蛋白日粮为对照,按照等能、等氮取代的原则研究了肉牛精料补充料中添加羟甲基脲、尿素和糊化淀粉尿素对肉牛生产性能和氮代谢的影响。植物蛋白组、糊化淀粉尿素组、羟甲基脲组和尿素组的日增重分别为0.756kg、0.735kg、0.833kg、0.806kg,其中羟甲基脲组明显高于糊化淀粉尿素组(P<0.05),其它组间差异不显著(P>0.05)。氮素利用效率(沉积氮／食入氮)与日增重趋势相一致。血清尿素氮以尿素组最高,其次是糊化淀粉尿素组,再次是羟甲基脲组,植物蛋白处理组最低。添加使用各种NPN没有对肉牛血液生化指标造成不良的影响。
试验七、不同水平羟甲基脲对绒山羊生产性能的影响。用羟甲基脲分别取代基础日粮中22%、34%和46%的豆粕,研究不同添加水平羟甲基脲对辽宁绒山羊增重和产绒效果的影响。结果表明各处理之间日增重和产绒量差异不显著。但22%处理、34%处理和46%处理分别比对照组增收30%、51%和35%。经济效益显著。
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. MethylolureaⅠ100% disappeared from nylon bags within 4 hours of incubation. MethylolureaⅡdisappeared 100% until 12 hours after incubation and methylolureaⅢ91% disappeared from nylon bag by 30 hours after incubation. So it was concluded that MethylolureaⅡand methylolureaⅢmight 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 methylolureaⅡwere 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,mythylolureaⅠtreatment, mythylolureaⅡtreatment and mythylolureaⅢtreatment, respectively. The total VFA production of mythylolureaⅡtreatment was also the highest among different treatments. The dynamic ammonia release pattern of mythylolureaⅡand mythylolureaⅢtreatment treatment was more stable than other treatments. However, the ammonia concentration of different time in fermentators of mythylolureaⅡtreatment were higher than that of mythylolureaⅢtreatment. So it concluded that mythylolureaⅡmight 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.
引文
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