【摘要】 为探索荷斯坦牛乳中尿素氮(Milk Urea Nitrogen,MUN)含量变化规律,利用最小二乘法对江苏某大型奶牛场5008头中国荷斯坦奶牛2010年1月到2013年12月98 882条DHI测定日记录中的MUN含量进行了分析。研究表明:该牛场MUN含量为(12.30±0.01)mg/dL,不同年度、测试季节、产犊季节、泌乳月和胎次对MUN含量的影响均达到极显著水平(P<0.01)。其中2013年MUN含量显著高于其余三年;夏季测定的MUN含量较高,冬季较低;冬季产犊的奶牛乳中MUN含量显著高于其余三个季节,夏秋两季产犊的MUN含量最低;第7、8泌乳月的MUN含量最高,第1个泌乳月的MUN含量最低,且差异显著;各胎次间MUN含量差异显著,其中第三胎的MUN含量最高,第一胎最低。该结果可指导牧场重点关注夏冬两季、泌乳前期及冬季产犊奶牛乳中的MUN含量。此外,各胎次间乳中的MUN含量也应区别对待,并根据变化趋势合理调整奶牛日粮配方,以期提高牧场管理水平和经济效益。更多还原

【Abstract】 In order to investigate the variability of milk urea nitrogen of Holstein in China,the data of98 882 DHI test day records for 5008 Chinese Holstein from the large dairy farm of Jiangsu since Jan.2010 to Dec.2013 was analyzed by the method of least mean squares.The results showed that MUN content of this dairy farm was 12.30±0.01mg/dL,and the MUN content was affected extremely by different years,seasons,calving seasons,lactating months and parities(P<0.01).The MUN content in 2013 was significantly higher than other years.MUN content in summer was significantly higher than other seasons,and the minimum MUN content was observed in winter.The MUN content of dairy cow calving in winter was significantly higher than the cows calving in other seasons,while the MUN content of cows calving in summer and autumn were the lowest.The minimum MUN content was observed in the first month of lactation,and then it peaked from 7to 8month of lactation.MUN content was significantly different among parities,which was the lowest in the first parity,and highest for third parity.These results could guide the dairy farms to focus on the MUN content of cows during summer and winter,early lactation and calving cows in winter.In addition,the MUN content among different parities should be treated differently.The diet formula should be adjusted according to the variation trend of MUN content in order to improve the management and economic benefits of dairy farm.更多还原