Some aspects of milk that elicit non-nutritive sucking in the calf

This experiment examined which aspects of milk ingestion elicited non-nutritive sucking in calves. Male dairy calves were allowed to suck a non-nutritive teat after meals of either cows' milk or milk replacer, and the amount of non-nutritive sucking that occurred during the 10 min following the meal was observed. There were no differences between milk and commercial milk replacer in the amount of non-nutritive sucking elicited. In later experiments, the calves were given small quantities (5–50 ml) of various liquids, either in a bucket or by syringe, allowed to suck the teat, and the non-nutritive sucking during the subsequent 2 min was observed. Non-nutritive sucking was greater after the calves were given milk replacer rather than water, and milk replacer continued to elicit non-nutritive sucking in calves weaned off milk 14 days previously. Non-nutritive sucking increased as the concentration of milk replacer was increased to 300% of normal concentration. A suspension of ground-up grain, and water solutions of casein and whey proteins did not elicit more non-nutritive sucking than water. Post-prandial non-nutritive sucking was elicited specifically by the ingestion of milk, and this was related to the concentration of the milk. However, the concentrations of the protein components alone appear not to be responsible for this effect.