THE MOTIVATION OF NONNUTRITIVE SUCKING IN CALVES, BOS-TAURUS

Although non-nutritive sucking is common, the motivation is poorly understood. The motivation of non-nutritive sucking in dairy calves was examined by independently varying milk intake and prior opportunities for non-nutritive sucking and observing calves sucking at a non-functional teat. Small amounts of milk elicited non-nutritive sucking, suggesting a relatively inflexible response to the taste of milk. Reinforcement from milk was not needed to maintain sucking. When calves were given less than the normal volume of milk, their subsequent non-nutritive sucking was not affected, but calves on a low-feed level sucked more, and those that missed a meal increased sucking after a subsequent meal. When calves sucked after ingesting milk they sucked less after immediately ingesting further milk. Thus, sucking motivation is reduced more by sucking behaviour than by milk intake, although it is not completely independent of hunger. Deprivation of non-nutritive sucking after one meal did not increase sucking 40 min later or sucking after subsequent meals. Thus, sucking motivation does not continue to accumulate across bouts. Non-nutritive sucking by precocial calves has some, but not all of the properties of Lorenzian processes.