Time Budget and Rumen Development of Dairy Calves around the Time of Weaning
The objective of this study was to develop tools to aid in the evaluation of the success of weaning programs for dairy calves, including physiological and behavioural measures and daily time budgets for calves at this stage of life. The study followed 10 ad libitum milk-fed Holstein calves for 24 d: pre-weaning (d 33 - 39 of age), during weaning (d 40 - 49 of age), and post-weaning (d 50 - 56 of age). During weaning, milk replacer was incrementally diluted on d 40, d 43, d 46 and d 49 by 25, 50, 75 and 100%, respectively. Calves were individually housed until weaning was complete (d 49), at which time each calf was paired. Feed intakes were recorded daily. Calves were weighed 2x/wk. Rumination time was observed by live 60-sec scans between 1200 and 1300h on alternate days beginning on d 34 and ending on d 56. Blood beta-hydroxybutyrate (BHBA) concentration was recorded daily, using a calf-side test, on the same schedule. Electronic data loggers continuously recorded standing and lying behavior for the duration of the trial. A mixed effect regression model provided insight on changes from pre- to post-weaning. Starter DMI increased from pre-weaning to post-weaning (51.7 to 3984.5 g DM/calf/d, SE= 160.0; P<0.001). BHBA increased from pre-weaning to post-weaning (0.003 to 0.133mmol/L, SE=0.01; P<0.001) as consumption of concentrate increased. Rumination time decreased from pre-weaning to post-weaning (7.9 vs. 2.9 min/h, SE=1.4; P<0.043). Standing time increased (5.95 to 8.03h/d; SE= 0.16), while both lying time (18.1 to 17.2 to 16.0h/d; SE= 0.16) and lying bouts (21.7 to 18.1 to 16.9 bouts/d; SE= 0.46) decreased from pre-weaning to weaning and again from weaning to post-weaning (P<0.001). The results indicate that these physiological and behavioral measures accurately assess rumen capabilities, daily time budgets, and calf comfort around the time of weaning. Further, BHBA measurements show promise in indicating rumen development in dairy calves.
Keywords: dairy calf, weaning, time budget