Ropstad E, Refsdal A O
Acta Vet Scand. 1987;28(1):55-63. doi: 10.1186/BF03548256.
Bulk milk samples were collected from 256 dairy herds from 4 districts in Southern Norway: Gudbrandsdal (n = 35), Bergen (n = 15), Hedmark (n = 117) and Hardanger (n = 89). A total of 6–8 samples were collected in each herd during the indoor season. Data concerning reproductive performance, milk production and nutrition were registered for a period of 15 months starting 7 months before the first milk sample was collected. The urea levels obtained during the sampling period were averaged generating a mean urea level of each herd. The mean urea levels were related to reproductive performance. The urea levels within districts showed only minor variations during the sampling period. The mean urea level in Hardanger was significantly higher (p < 0.05) than in the other distrikts. This district also had the lowest fertility. Significant correlations between mean urea level and fertility were observed only in Hedmark. Fertility status (FS), an integrated index, and number of inseminations per animal inseminated were significantly affected by the interaction between mean urea level and district. Herds in Hardanger with cows treated for ovarian cysts had a significantly higher mean urea level (p = 0.02) than herds with non-treated cows. The results appear to support the notion that a negative relationship may exist between bulk milk urea levels and reproductive performance. The great district variations observed indicate, however, that the practical value of such measurements is limited.
从挪威南部4个地区的256个奶牛场采集了大量牛奶样本：古德布兰斯达勒（n = 35）、卑尔根（n = 15）、海德马克（n = 117）和哈当厄（n = 89）。在室内饲养季节，每个牛场共采集6 - 8个样本。从采集第一个牛奶样本前7个月开始，记录为期15个月的繁殖性能、产奶量和营养数据。对采样期间获得的尿素水平进行平均，得出每个牛场的平均尿素水平。将平均尿素水平与繁殖性能相关联。在采样期间，各地区内的尿素水平仅显示出微小变化。哈当厄的平均尿素水平显著高于其他地区（p < 0.05）。该地区的繁殖力也最低。仅在海德马克观察到平均尿素水平与繁殖力之间存在显著相关性。繁殖力状态（FS）这一综合指标以及每头接受授精动物的授精次数受到平均尿素水平与地区之间相互作用的显著影响。对患有卵巢囊肿的奶牛进行治疗的哈当厄牛场，其平均尿素水平显著高于未治疗奶牛的牛场（p = 0.02）。结果似乎支持了大量牛奶尿素水平与繁殖性能之间可能存在负相关关系的观点。然而，观察到的地区差异很大，表明此类测量的实际价值有限。
