Fig. 2

Weekly intakes of calves began to consume forages at different ages (CON, EHAY, MHAY and LHAY). A Weekly forage intake of dairy calves. Asterisks (*) indicate differences (P ≤ 0.05) between groups (week1: LHAY < EHAY and MHAY; week 5: EHAY and MHAY < LHAY). Daggers (†) indicate trends (0.05 ≤ P ≤ 0.1) between groups (weeks 1: MHAY < EHAY; weeks 4: EHAY < LHAY). B Weekly forage intake ratio of dairy calves. Asterisks (*) indicate differences (P ≤ 0.05) between groups (week 1: LHAY < EHAY and MHAY). C Weekly NDF intake of dairy calves. Asterisks (*) indicate differences (P ≤ 0.05) between groups (week 8: CON and MHAY < LHAY; week 9 and 10: CON < LHAY; week 11 and 12: CON < EHAY, MHAY and LHAY). Daggers indicate trends (0.05 ≤ P ≤ 0.1) between groups (weeks 5 and 7: CON, EHAY and MHAY < LHAY). D Weekly ADF intake of dairy calves. Asterisks (*) indicate differences (P ≤ 0.05) between groups (weeks 8, 9 and 10: CON < LHAY; week 11: CON < MHAY and LHAY). Daggers indicate trends (0.05 ≤ P ≤ 0.1) between groups (weeks 7 and 12: CON < LHAY). Error bars represent ± SE. E Weekly peNDF intake of dairy calves. Asterisks (*) indicate differences (P ≤ 0.05) between groups (week1: LHAY < EHAY and MHAY; week 5: EHAY and MHAY < LHAY). Daggers (†) indicate trends (0.05 ≤ P ≤ 0.1) between groups (weeks 1: MHAY < EHAY; weeks 4: EHAY < LHAY). CON = Calves were fed starter concentrate without forage from d 1 to 84, HAY = Starter concentrate and forage were fed to calves as a free choice way from d 1 to 84, EHAY = calves began to consume forage at the earliest (from d 4 to 6), MHAY = calves began to consume the forage from d 7 to 9, LHAY = calves began to consume forage at latest (from d 10 to 15)