Nielsen N I, Larsen T, Bjerring M, Ingvartsen K L
Department of Animal Health, Welfare and Nutrition, Danish Institute of Agricultural Sciences, Research Centre Foulum, P.O. Box 50, 8830 Tjele, Denmark.
J Dairy Sci. 2005 Sep;88(9):3186-200. doi: 10.3168/jds.S0022-0302(05)73002-2.
Eleven Danish Holstein cows were used to examine the effects of quarter health (healthy vs. unhealthy), milking interval (12 vs. 6 h), and sampling time during milking on the concentration of 8 milk constituents [acetone, beta-hydroxybutyrate (BHBA), N-acetyl-beta-D-glucosaminidase (NAGase), somatic cell count (SCC), urea, fat, protein, and lactose]. The selection criterion was that each cow should have 2 or 3 healthy and 1 or 2 unhealthy quarters. Foremilk was collected before attaching the teat cups of the milking machinery, and thereafter, milk samples were collected automatically from each quarter every 45 s during milking. Compared with milk from healthy quarters, milk from unhealthy quarters had a higher concentration of BHBA, NAGase, SCC, and protein during the entire milking, whereas urea was higher in the last part of the milking process. Healthy quarters had a higher content of acetone and lactose during the whole milking, whereas fat was higher in the first part of the milking process. When the cows were milked at the 6-h interval, all milk constituents except lactose and protein were higher during the whole (NAGase, SCC, and urea) or part of the milking (acetone, BHBA, and fat) compared with when cows were milked at the 12-h interval. Lactose was higher in the first part of the milking at the 12-h compared with the 6-h interval, whereas protein was not affected by milking interval. beta-Hydroxybutyrate, NAGase, SCC, and fat increased during the milking process, whereas acetone, urea, protein, and lactose decreased. Foremilk was remarkably different for all constituents, except acetone, and should not be used as a representative milk sample to achieve the true level of a milk constituent. If these milk constituents are to be used in an inline management system, these effects should be taken into account.
选用11头丹麦荷斯坦奶牛，研究乳腺健康状况（健康与不健康）、挤奶间隔时间（12小时与6小时）以及挤奶过程中的采样时间对8种乳成分浓度的影响，这8种乳成分分别为丙酮、β-羟基丁酸盐（BHBA）、N-乙酰-β-D-氨基葡萄糖苷酶（NAGase）、体细胞计数（SCC）、尿素、脂肪、蛋白质和乳糖。选择标准为每头奶牛应有2或3个健康乳腺和1或2个不健康乳腺。在安装挤奶机的奶杯之前采集前乳，此后，在挤奶过程中每隔45秒自动从每个乳腺采集乳样。与健康乳腺的乳相比，不健康乳腺的乳在整个挤奶过程中BHBA、NAGase、SCC和蛋白质的浓度更高，而在挤奶过程的最后阶段尿素含量更高。健康乳腺在整个挤奶过程中丙酮和乳糖含量更高，而脂肪在挤奶过程的第一阶段含量更高。当奶牛以6小时的间隔挤奶时，与以12小时间隔挤奶相比，除乳糖和蛋白质外，所有乳成分在整个挤奶过程中（NAGase、SCC和尿素）或部分挤奶过程中（丙酮、BHBA和脂肪）的含量更高。与6小时间隔相比，12小时间隔挤奶时，乳糖在挤奶过程的第一阶段含量更高，而蛋白质不受挤奶间隔的影响。β-羟基丁酸盐、NAGase、SCC和脂肪在挤奶过程中增加，而丙酮、尿素、蛋白质和乳糖减少。除丙酮外，所有成分的前乳均有显著差异，因此前乳不应作为代表性乳样来获取乳成分的真实水平。如果将这些乳成分用于在线管理系统，则应考虑这些影响。
