Feeding behavior of calves fed small or large amounts of milk

Little is known about feeding behavior in group-housed calves fed with an automated feeding system. To examine the influence of milk feeding level on feeding behavior in such a system, we fed calves either 4 L of milk replacer per d (LIM) or allowed ad libitum (AL) intake (n = 25 per treatment). In a second experiment another set of calves was fed 4 L (low milk volume, LM) or 12 L (high milk volume, HM) of whole milk (n = 14 per treatment). Results were analyzed separately using a mixed model including calf, treatment, and time as factors, and feeding behavior as variables. Milk intake by AL or HM calves increased during the first 2 wk, reaching a maximum intake that reached a plateau during the next 4 wk. Concentrate intake was negligible during the first 14 d, with LIM and LM calves increasing their consumption from d 22. Concentrate intake by AL and HM calves remained low until weaning in experiment 1 and the end of trial in experiment 2 (d 43 for both). The frequency of visits was higher in LIM and LM calves than in AL and HM calves during the first 42 d, with most visits being unrewarded (approximately 90%). This resulted in higher occupancy time of the feeder by LIM and LM calves. During weaning in experiment 1 (d 44 to 48), there was no difference in occupancy time between treatments. Calves in the AL and HM groups distributed their visits throughout the day, whereas LIM and LM calves made most visits just before the time when the next allowance of milk became available. In experiment 1, AL calves showed a greater weight gain during the first 21 d but LIM calves had greater gains between d 22 and 50. However, the overall average daily weight gain was higher for AL calves. In experiment 2, HM calves had a greater gain than LM calves for the first 4 wk of trial but there was no difference between treatments during the last 2 wk. There were no differences between treatments in the incidence of disease in either experiment. The duration of time spent lying down in experiment 2 was higher for HM calves but only when they were older (4 to 5 wk). No differences were found between treatments at 2 wk of age. In conclusion, feeding high levels of milk or replacer improved weight gain and reduced unrewarded visits to the milk feeder, improving the efficiency of use of the milk feeders. However, it reduced concentrate intake and the advantages were less obvious after 3 wk of age. No increased incidence of disease was found for high-fed calves (AL and HM groups). Lying time was also higher for high-fed calves but only at an older age (4 to 5 wk).