Effect of omeprazole treatment on feed intake and blood gastrin and pepsinogen levels in the calf.

Previous work has shown blood gastrin levels to be elevated and appetite depressed in ostertagia-infected calves. A possible relationship between raised blood gastrin values and feed intake was investigated in worm-free animals using the human gastric acid secretion inhibitor, omeprazole. An initial dose-titration experiment established that administration of the drug by intravenous injection at 1.95 mg kg-1 (four times the recommended human dose rate) resulted in a marked (5.2-fold) increase in blood gastrin levels in the calf. Daily administration of omeprazole by intravenous injection at 2 mg kg-1 for four days in a subsequent experiment resulted in a significant depression in feed intake (up to 40.4 per cent) which was accompanied by a significant rise in blood gastrin levels (peak 940 pg ml-1; 6.5-fold increase over control values). It is suggested that such a rise in hormone levels would reduce reticuloruminal and abomasal motility, slow down the passage of ingesta and, in turn, lead to a reduction in appetite.