Sampling and Analyses
Blood samples were taken via the tail vein from all cows at dry-off, the day cows left the metabolism stalls (approximately 25 d before anticipated calving), and within 15 h after parturition. Blood from calves (jugularvein) was sampled within 15 h of birth. A sample of first milking colostrum was taken from each cow. Blood samples were collected into heparinized, trace metal free vacutainers, and colostrum samples were placed in acid-washed containers. Over the experiment (approximately 4 mo were required for all cows to finish the experiment), forages and concentrates were sampled weekly and composited into monthly samples. Weekly forage samples were analyzed for DM to adjust TMR for changes in forage moisture. During the metabolism study, feeds, orts (if any), urine, and feces were sampled daily (samples of orts, urine, and feces represented 10, 2, and 1%, respectively, of daily amounts) and were composited within cow. Feeds, orts, and fecal samples were lyophilized and ground (1-mm screen; Wiley mill; Arthur Thomas, Philadelphia, PA). Water samples were taken on approximately d 30 and 60 of the experiment during the second and third collection period (samples were taken from the water stream immediately before water entered the drinking cups).
