不同糊化淀粉尿素氮替代水平对泌乳中后期奶牛的安全性研究

Effects of Levels of Starea Nitrogen Replacement on the Safety of Dairy Cows in Mid-late Lactation Period

本试验旨在研究不同水平的糊化淀粉尿素氮对泌乳奶牛生产性能和氨氮水平以及三聚氰胺和三聚氰酸在乳中残留的影响,为糊化淀粉尿素在奶牛上的合理安全使用提供数据支持。试验选用5头安装有瘤胃瘘管的泌乳中后期荷斯坦奶牛为研究对象,采用5×5拉丁方试验设计,对照组饲喂不含尿素日粮,U-16%组用尿素氮替代日粮总氮的16%,S-16%、S-24%和S-32%组分别用糊化淀粉尿素氮替代日粮总氮的16%、24%、32%,第一期适应期14d,以后每期适应期7d,采样期5d,共67d,比较研究尿素氮和糊化淀粉尿素氮替代日粮总氮的不同水平对泌乳奶牛生产性能、瘤胃和血液氨浓度、血液尿素氮以及三聚氰胺和三聚氰酸残留的影响。研究结果表明,糊化淀粉尿素氮替代日粮总氮的16%、24%,奶牛生产性能与对照组相比均没有显著变化(P>0.05),血氨浓度正常,当糊化淀粉尿素氮替代水平达32%时,显著降低干物质采食量和产奶量(P<0.05);糊化淀粉尿素氮与尿素氮相比,能有效延缓氨浓度峰值出现时间,降低血氨浓度峰值,但是随着糊化淀粉尿素氮替代水平的升高瘤胃氨峰值和血氨峰值均升高;用糊化淀粉尿素氮替代日粮总氮的不同水平不会产生乳中三聚氰胺和三聚氰酸残留。因此,本研究得出,从安全性角度考虑,在泌乳奶牛上糊化淀粉尿素氮替代日粮总氮的适宜比例不宜超过24%。

The aim of this study was to evaluate the effect of starea nitrogen on production performance,ammonia nitrogen（N） concentration in rumen liquor and blood,blood urea N,and melamine and cyanuric acid residual in milk of lactating dairy cows.Five mid-late lactating Holstein cows with rumen fistula were divided into five groups in a 5×5 Latin square design.The cows of the five groups were fed with control diet without urea,U-16% diet with 16% of the total N of control diet replaced by urea N,and S-16%,S-24% and S-32% diet with 16%,24% and 32% of the total N of control diet replaced by starea N.The adaption period of the first phase was 14 d and the other phase was 7 d,respectively.The sampling period in every phase was 5 d.All of the experiment lasted for 67 d.The results showed that replacing 16% or 24% of the N in control diet with non protein nitrogen from starea did not affect the lactation performance significantly（P〉0.05）,but in the S-32% group the lactation cows had a reduced dry matter intake and milk production（P〈0.05）.Compared with urea,the starea could relieve ammonia concentration in rumen liquor and reduce the peak of blood ammonia concentration effectively,but the peak concentration of rumen ammonia and blood ammonia were also increased with the increasing of the starea.The starea could not cause melamine and cyanuric acid residual in milk.It is concluded that for the dairy cows’ safety the proper proportion of replacing the total nitrogen of diets with starea nitrogen is less than 24%.