Effects of resistance to milk flow and the provision of hay on nonnutritive sucking by dairy calves.

This study examined effects of resistance to milk flow and the provision of hay on the duration of nutritive sucking and subsequent nonnutritive sucking by dairy calves. In a series of four experiments, 12 male Holstein calves were individually fed milk from an artificial teat. Resistance to milk flow was varied by adjusting the orifice size within the milk supply tube. Using a Latin square design, each calf was fed the same quantity of milk using four orifice sizes (one per day for 4 consecutive d). The duration of nutritive sucking (time required to finish the milk meal) was longer when calves were fed from the smallest orifice size (0.16-cm diameter) than when calves were fed from the largest orifice size (0.55-cm diameter). Calves compensated for resistance to milk flow in an attempt to maintain milk intake; however, changes in sucking rate alone were probably not responsible for observed differences in the rate of milk consumption from different orifice sizes. The duration of nonnutritive sucking (sucking of the teat following the milk meal) was significantly reduced when calves were fed from the smallest orifice compared with that when calves were fed from the largest orifice. Nonnutritive sucking was reduced but not eliminated even with the longest meal duration. The provision of hay to calves following the meal also significantly reduced the amount of nonnutritive sucking. Reduction in flow rate when calves drink milk through a teat and the provision of hay after the meal can reduce the incidence of nonnutritive sucking following the meal and may help to limit cross-sucking in group housing systems.