Nonnutritive sucking by the calf and postprandial secretion of insulin, CCK, and gastrin

Early weaned calves were allowed to suck on a dry rubber teat after drinking milk, and samples of blood from the hepatic portal vein and from the jugular vein were assayed for insulin, CCK, and gastrin to determine if nonnutritive sucking affected digestive hormone secretion. Postprandial changes in concentrations of all hormones showed a biphasic response with an initial rapid increase, later followed by a slower increase. In the portal vein, peak postprandial concentrations of insulin and concentrations of CCK 60 min after the meal were higher when the calves could suck the teat after the meal. There was a positive correlation between the time spent sucking the teat and the increase in insulin and CCK concentrations. Nonnutritive sucking did not significantly increase gastrin concentrations, nor were concentrations of insulin and CCK in the jugular vein affected. The performance of normal appetitive feeding behavior can directly affect digestive hormone secretion even if nutrient intake is not affected. Deprivation of normal sucking behavior cannot be assumed to be inconsequential for the well being of calves.