Effect of orally administered cimetidine and ranitidine on abomasal luminal pH in clinically normal milk-fed calves

Objective-To characterize the change of pH In the abomasal lumen throughout a 24-hour period, to determine whether pH of the abomasal body differs fro m pH of the pyloric antrum, and to determine whether oral administration of cimetidine and ranitidine alters pH of the abomasal lumen In milk-fed calv es. Animals-5 male dairy calves (4 Holsteins-Friesian, 1 Ayrshire), 5 to 15 day s old. Procedure-Cannulas were surgically positioned In the abomasal body and pylo ric antrum of each calf. Calves received the following treatments in a rand omized crossover design: milk replacer (60 ml/kg of body weight, q 12 h [un treated control calves]), milk replacer and cimetidine (50 or 100 mg/kg, q 8 h), or milk replacer and ranitidine (10 or 60 mg/kg, q 8 h). The pH of th e abomasal body and pyloric antrum was measured for 24 hours, using miniatu re glass pH electrodes. Results-Suckling of milk replacer immediately increased abomasal luminal pH from 1.4 to 6.0, followed by a gradual decrease to preprandial values by 6 hours. Preprandial and postprandial pH values were not significantly diffe rent between the abomasal body and pyloric antrum, indicating lack of pH co mpartmentalization in the abomasum of milk-fed calves. Administration of ci metidine and ranitidine caused a significant dose-dependent increase in mea n 24-hour abomasal luminal pH. Conclusions and Clinical Relevance-Abomasal acid secretion in milk-fed calv es Is mediated in part by histamine type-2 receptors. Cimetidine and raniti dine may be efficacious in the treatment of abomasal ulcers in milk-fed cal ves.